Segment 1 Exam Review



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Segment 1 Exam Review

This review is neither a replica of the exam nor does it contain every concept in the module or what may be on the exam. This review contains only the concepts in the regular lessons. It is always best practice to review all lessons and assessments. Resubmitting is a great way to review/learn and improve your grade. In this review, questions 1 – 21 are the general topics for the multiple choice type questions on the module exam; questions 22-25 are covered as essays on the exam. There are approximately 61 questions (about 5 are essays) on the regular exam; approximately 74 questions (about 10 are essays) on the honors exam. The number in parenthesis corresponds to the lesson for that question.



Student Help Site (Teaching videos and all module reviews): http://bit.ly/ZtUhQK

Multiple Choice Topics

  1. What is science? (1.02)



  1. Define pseudoscience and list one example. (1.02)



  1. How can we increase the scientific reliability of scientific claims? (1.02)




  1. Describe important factors when testing a hypothesis. (1.02)




  1. Explain why the model of the atom has changed so much. (1.02)



  1. Why is it important to test alternative explanations to hypothesis? (1.03)



  1. Compare scientific theory and scientific law. (1.03)



  1. An infomercial claims their product will grow hair in 2 weeks. It has been advertised in many popular magazines as well. How could the company increase the scientific reliability of this claim? (1.03)



  1. Explain what a scientist could do to contribute to the strength of a scientific theory. (1.03)



  1. Environmental scientists and biologists investigate the causes of global warming. Explain how having scientists with different backgrounds and expertise will affect the predictions made by the group of scientists. (1.03)



  1. Scientists tracking the extinction of certain animals have found a sudden increase in the population of one species. One group of scientists have analyzed the data and hypothesized that new laws preventing hunting of this species have contributed to this change in population. Another group of scientists have hypothesized that this population trend is part of a cycle related to ecosystem changes. If these two groups of scientists have access to the same population data, describe how they could have formed two very different hypotheses. (1.03)



  1. A scientist in America published her findings from a scientific investigation that she conducted. What could this scientist do in order to strengthen the findings of her investigations? (1.03)



  1. According to the lesson, “Observation and experimentation have led some scientists to accept a theory about the origin of the universe, known as the Big Bang Theory. Scientific evidence suggests that our universe is ever-expanding from a hot and dense initial state. Some evidence that supports this theory is cosmic microwave background radiation that is uniform throughout the universe. This supports the notion that the gas which emitted this radiation long ago was very uniformly distributed.” Why is this considered a theory and not a law? (1.02-1.03)



  1. List 4 types of equipment commonly found in the lab and identify what it measures. What equipment do we need to determine density of a liquid? (1.04)



  1. Compare kinetic and potential energy; include at least 4 types of each. (1.05)



  1. Give an example of a situation where potential energy is being converted into

kinetic energy. (1.05)

  1. Define temperature. Give three common units to measure temperature. (1.05)



  1. Convert 2.34 cm to nm. (1.06)



  1. Is the following group of data accurate, precise, both or neither if the true measurement is 13.74 cm? Data collected: 12.45 cm, 12.75 cm, 12.52 cm. (1.07)



  1. How many significant figures are in the measurement 0.02040 cm? (1.07)



  1. Describe the implications of Rutherford’s experiment. (2.01)



  1. Why do theories sometimes evolve over time? (2.01)



  1. Describe the implications of Thomson’s cathode ray experiment. (2.01)



  1. How many protons, neutrons and electrons are in an atom of sulfur? (2.02)



  1. An atom has 50 electrons, 52 protons and 67 neutrons. What is the atomic mass and overall charge of this atom or ion? What is the identity? (2.02)



  1. Does chlorine-34 have the same number of neutrons as calcium-40? (2.02)



  1. The atomic and mass numbers for four different atoms are given below. Which two are isotopes? (2.03)



Atom

Atomic Number

Atomic Mass (amu)

A

29

63

B

30

63

C

29

65

D

28

65



  1. How many atoms are in 24.9 g of Al? (2.04)



  1. How many grams of gold are there in 5.35 moles? (2.04)



  1. Which of the following contains the greatest mass? (2.04)

    1. 23.7 g C

    2. 2.10 moles C

    3. 6.45 X 1023 atoms C



  1. Describe what happens when a gaseous atom is placed in a flame. (2.05)



  1. What is a line spectrum? (2.05)



  1. Describe how energy, frequency and wavelength are related. (2.05)



  1. What is the general electron configuration for a noble gas? (2.06)



  1. What would be the most likely charge of an ion formed from an atom with the electron configuration: 1s22s22p63s23p3 (2.06)



  1. Compare Moseley and Mendeleev’s periodic tables. (3.01)



  1. Explain how the modern periodic table was derived. (3.01)



  1. Could the following pair of elements, A and B, possibly be in the same group on the periodic table? Explain why or why not. (3.02)

A tends to form a 1+ ion; B tends to gain one electron.

  1. Identify at least 1 element that Lithium would have properties most similar to. (3.02)



  1. Does the following ordered pair of elements show a decrease in ionization energy and an increase in radius? (3.03)

Cl and F

  1. Which element on the periodic table has the smallest atomic radius? (3.03)



  1. Identify a compound which experiences hydrogen bonding. (3.07)



  1. Identify a compound which contains only single bonds? (3.06)



  1. Identify a compound which contains both ionic and covalent bonds? (3.06)



  1. What will be the formula of a compound formed by magnesium and phosphorus? (3.05/3.08)



  1. What is the name of the acid with the formula HNO3? (3.08)



  1. What is the name of the acid with the formula H3N? (3.08)



  1. What is the name of the compound Pb(SO4)2? (3.08)



  1. What is the molar mass of Pb(SO4)2? (2.04/3.09)



  1. Define physical and chemical properties. (4.01)



  1. List three physical and three chemical properties. (4.01)



  1. Define extensive and intensive properties. Give an example of each. (4.01)



  1. When the following reaction is balanced with the lowest possible whole number coefficients, what is the coefficient in front of CO2? (4.02)

C2H4 + O2 CO2 + H2O

  1. Pick two chemicals, that when placed together would NOT produce a successful single-replacement reaction. (4.03)

  2. What is the balanced equation when sulfur trioxide reacts with water? (4.04)



  1. If 4.65 moles of barium react with excess bromine gas, how many grams of barium bromide can be produced? (4.06) Equation: Ba + Br2 BaBr2



  1. When 2.6 mol HCl react with 9.6 mol Mg(OH)2, what is the limiting reactant and how many moles of H2 can be formed? (4.07)

unbalanced equation: Mg(OH)2 + HCl MgCl2 + H2O

  1. If the reaction of 3.75 moles of lithium with excess hydrofluoric acid produced a 96.5% yield of hydrogen gas, what was the actual yield of hydrogen gas? (4.08) Unbalanced equation: Li + HF LiF + H2

Essay Topics


  1. Create a question that can be tested through science. Create a question that cannot be tested through science Explain why these can or cannot be. (1.02)



  1. Pick one scientist (Dalton, Crookes, Thomson, Rutherford or Chadwick) and explain how the experiment led to specific changes to the model of the atom. (2.01)



  1. Write the complete balanced equation for the reaction between LiNO3 and Mg3P2. (4.02-4.05)



  1. List one of the products that forms when Mg(OH)2 decomposes. (4.04)



  1. Write the balanced equation for the combustion of C5H12. (4.05)



  1. If 5.24 grams of sodium nitrate reacts with 4.35 grams of aluminum phosphate to produce 2.50 g of sodium phosphate, what are the theoretical yield and percent yield of this reaction? Be sure to show the work that you did to solve this problem. (4.06-4.08) unbalanced equation: NaNO3 + AlPO4 Na3PO4 + Al(NO3)3


Segment 1 Exam Review ANSWER KEY

Multiple Choice Topics

  1. What is science? (1.02)

Science is the effort to increase an understanding of the world around us by using the knowledge acquired and to acquire new knowledge.

  1. Define pseudoscience and list one example. (1.02)

A pseudoscience is a practice or belief that claims to be science, but does not or cannot follow the scientific method. Astrology is an example.

  1. How can we increase the scientific reliability of scientific claims? (1.02)

We can increase the reliability by having the hypothesis tested by an independent organization. The greater number of scientists throughout the globe who conduct the experiment will increase the strength of any claim.

  1. Describe important factors when testing a hypothesis. (1.02)

A scientist should be unbiased, having no stake in the outcome of the experiment. The scientist should use creativity to design experiments and have other scientists test the hypothesis by conducting their own experiments. Once data is collected, the scientist should look at the variables to ensure this is the only explanation.

  1. Explain why the model of the atom has changed so much. (1.02)

Objective experimentation by independent organizations across the globe have brought about new discoveries which enhances our knowledge. Therefore, we must revise our current theories.

  1. Why is it important to test alternative explanations to hypothesis? (1.03) Ans: A scientist will strengthen support for a theory if he continues to test alternative explanations and determine them to be invalid. Without testing alternative, we can never be sure that the results we get are truly the only explanation.



  1. Compare scientific theory and scientific law. (1.03)

A scientific theory tries to explain why things happen the way they do in the natural world. A scientific law tells us what happens in nature (does NOT explain why). Remember this: Law is the ‘what’; theory is the ‘why’. A theory NEVER becomes a law as a why cannot become a what. Those are two completely different concepts.

  1. An infomercial claims their product will grow hair in 2 weeks. It has been advertised in many popular magazines as well. How could the company increase the scientific reliability of this claim? (1.03)

To increase reliability, an experiment should be repeated by independent organizations across the globe by scientists who are objective and gain nothing from the outcome.

  1. Explain what a scientist could do to contribute to the strength of a scientific theory. (1.03)

To increase the strength of a theory, a scientist should have numerous independent organizations across the globe test the theory by conducting their own experiments; these organizations should represent a variety of points of view, consider alternative explanations, and use creativity to design their experiments.

  1. Environmental scientists and biologists investigate the causes of global warming. Explain how having scientists with different backgrounds and expertise will affect the predictions made by the group of scientists. (1.03)

Scientists with diverse backgrounds and specialties will strengthen an experiment/theory as it shows that regardless of the specialty, the scientists agree on the results.

  1. Scientists tracking the extinction of certain animals have found a sudden increase in the population of one species. One group of scientists have analyzed the data and hypothesized that new laws preventing hunting of this species have contributed to this change in population. Another group of scientists have hypothesized that this population trend is part of a cycle related to ecosystem changes. If these two groups of scientists have access to the same population data, describe how they could have formed two very different hypotheses. (1.03)

Scientists with different backgrounds and specialists may interpret data differently. This will cause the need for more experimentation and data collection.

  1. A scientist in America published her findings from a scientific investigation that she conducted. What could this scientist do in order to strengthen the findings of her investigations? (1.03)

This scientist could have an independent organization formed by diverse scientist’s test her hypothesis by conducting experiments.

  1. According to the lesson, “Observation and experimentation have led some scientists to accept a theory about the origin of the universe, known as the Big Bang Theory. Scientific evidence suggests that our universe is ever-expanding from a hot and dense initial state. Some evidence that supports this theory is cosmic microwave background radiation that is uniform throughout the universe. This supports the notion that the gas which emitted this radiation long ago was very uniformly distributed.” Why is this considered a theory and not a law? (1.02-1.03)

A theory explains why something happens. In this example, the scientists are attempting to explain what their data shows. A law has been tested again and again and is accepted as what happens.

  1. List 4 types of equipment commonly found in the lab and identify what it measures. What equipment do we need to determine density of a liquid? (1.04)




Equipment:

Measures this variable:

Variable Units:

Graduated cylinder

volume

mL (base unit: L)

Triple beam balance

Mass

Kg, g (base unit: g)

Digital balance

mass

Kg, g (Base unit: g)

Ruler

length

in, cm, (base unit: m)

For a liquid, we need balance and a graduated cylinder

density

g/L, g/mL (common unit: g/L)




  1. Compare kinetic and potential energy; include at least 4 types of each. (1.05)

Potential energy is stored energy. Examples include: stored mechanical energy, chemical, nuclear and gravitational energy. Kinetic energy is energy in motion. Examples include: mechanical, electrical, radiant, sound and thermal energy.

  1. Give an example of a situation where potential energy is being converted into

kinetic energy. (1.05)

A ball that was sitting atop a hill begins moving down the hill. At the top, the ball has potential energy while it is sitting. The potential energy is converted into kinetic energy when the ball begins rolling down the hill.



  1. Define temperature. Give three common units to measure temperature. (1.05)

Temperature is the measure of a substances average kinetic energy. Three common units are the Kelvin, degrees Celsius (°C) and degrees Fahrenheit (°F – only in America)


  1. Convert 2.34 cm to nm. (1.06)

There are many ways to do this type of problem by simply moving the decimal the correct number of places or by using dimensional analysis. I personally like to convert back to the main unit (meters in this case), then to the other unit. This prevents a lot of silly errors that can occur when trying to take short cuts.

2.34 cm X X = 2.34 X 107 nm



  1. Is the following group of data accurate, precise, both or neither if the true measurement is 13.74 cm? Data collected: 12.45 cm, 12.75 cm, 12.52 cm. (1.07)

This data is pretty close to one other; therefore, they are considered precise. The group of data is not close to the accepted value of 13.74; therefore they are not accurate.

  1. How many significant figures are in the measurement 0.02040 cm? (1.07)

There are 4 significant figures 0.02040 cm. Here is a quick explanation if you have difficulty in which I explain all the rules into two basic categories:

(1) Do not have a decimal: zeros at the end don't 'count'

Ex: 10 (1 sig figs)

Ex: 250 (2 sig figs)

Ex: 40490 (4 sig figs)

(2) If you do have a decimal: everything after the first nonzero 'counts' (including the non-zero)

Ex: 10.0 (3 sig figs)

Ex: 0.025 (2 sig figs)

Ex: 0.0040901 (5 sig figs)


  1. Describe the implications of Rutherford’s experiment. (2.01)

Rutherford designed his experiment to further support Thomson’s model of the atom. Bohr believed that the small particles were evenly distributed throughout the entire atom. In Rutherford’s experiment, he shot positive alpha particles at a small piece of gold foil (hence the name of the experiment). He expected all of the alpha particles to pass through the foil, undeterred. What he actually saw was that most of the particles did pass through. However, a random particle hit something and got deflected, sometimes coming back at him. This was extremely surprising giving the speed of the alpha particles. He concluded that there must be something small, dense and positive (deflected, not attracted positive alpha particles) in the center of the atom. He named it the nucleus. This caused the scientific community to reevaluate and amend the atomic model of the atom.

  1. Why do theories sometimes evolve over time? (2.01)

Theories change over time due to new experimental evidence which has been corroborated by independent scientists.

  1. Describe the implications of Thomson’s cathode ray experiment. (2.01)

Thomson used the cathode ray tube and discovered the atom had another small particle which had a negative charge. Today, we call these particles the electron. .

  1. How many protons, neutrons and electrons are in an atom of sulfur? (2.02)

Sulfur has an atomic number of 16 and an atomic mass of approximately 32 amu. The atomic number tells us the number of protons.

16 protons

We are speaking of an atom, which is electrically neutral. Therefore, the number of protons (positive) must equal the number of electrons (negative).

16 protons = 16 electrons

The atomic mass is the sum of protons and neutrons. The mass of sulfur is 32. Therefore there is a total of 32 protons and neutrons. We have already determined that sulfur has 16 protons. So, 32 = 16 + neutrons.

16 neutrons.



  1. An atom has 50 electrons, 52 protons and 67 neutrons. What is the atomic mass and overall charge of this atom or ion? What is the identity? (2.02)

The atomic mass is the sum of protons and neutrons: 52 protons + 67 neutrons = 119 amu.

To determine the overall charge, we must look at the number of protons (positive) and electrons (negative):

52 protons (+)

50 electrons (-)

Overall charge = 2+ (2 extra positives gives a 2+ charge)

To determine the identity, we look up the atomic number. Recall the number of protons equals the atomic number. This ion has 52 protons, so its atomic number is 52. Tellerium, Te, is the element on the periodic table with an atomic number of 52.



  1. Does chlorine-34 have the same number of neutrons as calcium-40? (2.02)

We must determine how many neutrons each of these isotopes have. The number after the name is the atomic mass, which is the sum of protons and neutrons. The atomic number on the periodic table tells us the number of protons.

Chlorine-34. Mass = 34. Atomic number = 17. So, this isotope has 17 protons and a total of 34 protons and neutrons.

34 = 17 + neutrons

Neutrons = 17

Calcium-40. Mass = 40. Atomic number = 20. So, this isotope has 20 protons and a total of 40 protons and neutrons.

40 = 20 + neutrons

Neutrons = 20

To answer the question: No, these two isotopes do not have the same number of neutrons.



  1. The atomic and mass numbers for four different atoms are given below. Which two are isotopes? (2.03)



Atom

Atomic Number

Atomic Mass (amu)

A

29

63

B

30

63

C

29

65

D

28

65

To be isotopes of the same element, they must have the same number of protons, which is the same atomic number. Atoms “A” and “C” both have an atomic number of 29. These two are isotopes of the same element.

  1. How many atoms are in 24.9 g of Al? (2.04)

Always start with what you are given. Then, ‘follow the units’. Whatever unit you start with MUST be on the bottom of the first conversion. We can ONLY do certain conversions. Here is a flowchart to help you.

24.9 g Al X X = 5.57 X 1023 atoms Al

Molar mass of Al Avogadro’s #


  1. How many grams of gold are there in 5.35 moles? (2.04)

5.35 moles Au X = 1050 g Au (1053.4 rounded to 3 sig figs)

Molar mass of Au



  1. Which of the following contains the greatest mass? (2.04)

    1. 23.7 g C

    2. 2.10 moles C

    3. 6.45 X 1023 atoms C

In order to ascertain which of these three has the greatest mass, we must convert all of them to grams (unless you really understand the scale of units-most don’t until years of practice).


  1. 23.7g C



  1. 2.10 moles C X = 25.22 g C




  1. 6.45 X 1023 atoms C X X 12.86 grams C

Comparing the three masses, sample “B” has the greatest mass.

  1. Describe what happens when a gaseous atom is placed in a flame. (2.05)

When we place a gaseous atom into a flame, it will gain energy. The valence electrons will jump up into higher orbitals, which we call the excited state. This is very unstable, so the electrons will eventually release that energy as they fall back down to lower energy levels. As an electron falls, energy equal to the difference between the two orbits is emitted in the form of light, which we see as visible light.

  1. What is a line spectrum? (2.05)

According to the lesson, “When atoms in the gas state are heated, they give off light. Each element produces its own unique color when heated. You have seen examples of this in neon lights and fireworks. Scientists used prisms to examine the light emitted by these heated elements. They observed that each element produces a unique pattern of lines, called a line spectrum, instead of a continuous rainbow.” The hydrogen line spectrum:





  1. Describe how energy, frequency and wavelength are related. (2.05)

Energy and frequency are directly related. As the energy increases, so does the frequency. Energy/frequency and wavelength are indirectly proportional. As the energy (and thus frequency) increases, the wavelength will decrease (get shorter).

  1. What is the general electron configuration for a noble gas? (2.06)

All noble gases have a full valence shell. Which shell it is, depends on which period they are in on the periodic table.

A few examples: 1s22s22p63s23p6



1s22s22p63s23p64s24p6

Notice the highest energy level (largest big number) has a total of 6 electrons (superscripts). I have colored these blue.



  1. What would be the most likely charge of an ion formed from an atom with the electron configuration: 1s22s22p63s23p3 (2.06)

To determine what the most likely charge is, we must determine how many electrons are in the valence shell. The valence shell is the outermost (or highest) energy level. 1s22s22p63s23p3. For this element, we see there are 5 electrons in the valence shell. Elements want to have 8. So, thinking of just the numbers, is it ‘easier’ to gain 3 electrons (to have a total of 8) or to lose 5 electrons? If you guessed gain 3, you are correct! If we gain 3 electrons, we would have an overall charge of 3-.

  1. Compare Moseley and Mendeleev’s periodic tables. (3.01)

Mendeleev arranged his periodic table in order of increasing atomic mass. This left spaces and special situations in which elements had to be out of mass order in order to fit in the reactivity trend.

Moseley arranged his periodic table in order of increasing atomic number, which he realized equaled the number of protons. This fixed the issues Mendeleev had with his table.

Moseley’s atomic number supported and justified the observed periodic properties of elements and the organization of elements on Mendeleev’s periodic table.


  1. Explain how the modern periodic table was derived. (3.01)

The periodic table was arranged so that elements with similar properties were arranged in rows and columns. By arranging the elements in increasing atomic mass, a “periodic” trend of properties was noticed.

  1. Could the following pair of elements, A and B, possibly be in the same group on the periodic table? Explain why or why not. (3.02)

A tends to form a 1+ ion; B tends to gain one electron.

If “A” tends to form a 1+ ion, which means it loses one electron. “B” tends to gain one electron, which forms a -1 charge (electrons are negative). The periodic table is arranged so that elements in the same group (vertical column) often form the same charge. Therefore, these two elements are not likely found in the same group on the periodic table. In fact, they are on opposite sides!

  1. Identify at least 1 element that Lithium would have properties most similar to. (3.02)

The periodic table is arranged so that elements in the same group have similar properties and valance electrons. Therefore, any of the elements found in the same group as Li would have similar properties. Lithium in an alkali metal, and is found in group 2. Na is an atom that would have similar properties.

  1. Does the following ordered pair of elements show a decrease in ionization energy and an increase in radius? (3.03)

Cl and F

For this, we must know the trends. Cl is lower than F on the periodic table, but they are in the same column/group. Ionization energy increases as you go left to right, decreases as you go top to bottom. Therefore, we would expect elements on the right-top to have the highest ionization energy.

That is only half of this. Atomic radius decreases slightly as you go left to right, and increases top to bottom. Therefore, the largest element is on the bottom-left.

To go from Cl to F, we are going up the periodic table. This is an increase in ionization energy and a decrease in radius. To answer the question: no, they do not.





  1. Which element on the periodic table has the smallest atomic radius? (3.03)

Atomic radius decreases slightly as you go left to right, and increases top to bottom. Therefore, the smallest element is at the top-right, which is He.

  1. Identify a compound which experiences hydrogen bonding. (3.07)

Hydrogen bonding is where hydrogen is directly bonded to F, O or N. Any compound that has this combination would experience hydrogen bonding. There are numerous examples, including water, H2O and ammonia, NH3.

Some non-examples include CH3 and H3P.



  1. Identify a compound which contains only single bonds. (3.06)

There are thousands of examples that you could pick. You must accurately draw the Lewis Dot Structure to determine how many bonds there are. CH4 is a common example of a compound with only single bonds.

C has 4 valance electrons. When draw the LDS for C, remember there is one electron on each side (represents an orbital – 4 max) before the double up.



H has 1 valence electron, there are 4 of them.



Arrange H so that each one can bond with C’s valence electrons



This compound forms 4 single covalent bonds.

  1. Identify a compound which contains both ionic and covalent bonds? (3.05-3.08)

In order to have both ionic and covalent, we must have an ionic compound with a polyatomic ion. Therefore, we need a metal + polyatomic. A few examples:

NaNO3, LiOH and AlPO4



  1. What will be the formula of a compound formed by magnesium and phosphorus? (3.05/3.08)

We must have the ‘common charges’ (found in the lesson, click on “using the periodic table’)

Mg is in group 2, and it forms a common charge of +2

P is in group 5 and it forms a common charge of -3.

So, how many of each do we need to be neutral overall (zero)?

Mg+2 P-3

Mg+2 P-3



Mg+2

+6 -6 = 0

So, we need 3 magnesium ions and 2 phosphorus ions in order to be neutral. Those will be their respective subscripts.

Mg3P2



  1. What is the name of the acid with the formula HNO3? (3.08)

This acid is made with the nitrate polyatomic ion. I know this because there are 3 or more different elements (indication you have a polyatomic ion).

This polyatomic ion ends in –ate, and we learned to change the ending to –ic and and the word acid. So, we get: nitric acid.



  1. What is the name of the acid with the formula H3N? (3.08)

This is a binary (only 2 atoms) acid. For this type of acid, we will use the ‘hydro’ suffix and the word acid at the end: hydro__________ acid.

So, now we need to figure out what the middle part is. The acid has the element N in it, which is commonly referred to as nitride. For binary acids, we always change the ending to –ic. So, we get: hydronitric acid.



  1. What is the name of the compound Pb(SO4)2? (3.08)

Pb is lead, and is a ‘special’ metal meaning it requires a roman numeral indicating its charge. We must figure out its charge from the formula.

There is one Pb and two sulfates. We know Pb is positive because it is a metal and it is written first. Pb?+ Sulfate is a polyatomic ion which always has the same charge: SO42-

If it took 1 Pb to balance 2 sulfates (total of 4- charge), what must the charge of Pb be?

Pb?+ SO42-



SO42-

(+ ?) (- 4) = 0

The charge must be +4. Pb +4.

So, we will name that compound lead (IV) sulfate.



  1. What is the molar mass of Pb(SO4)2? (2.04/3.09)

Molar mass is the mass, in grams, of one mole of your substance according to the periodic table.

So, we need to determine how many atoms of each element we have:

Pb x 1

S X 2


O X 8 (there are 4 O’s in each sulfate ion, but there are two sulfate ions)

Let’s look up their masses on the periodic table and multiply by how many we have:

Pb = 207.2 X 1 = 207.2

S = 32.06 X 2 = 64.12

O = 16 X 8 = 128

Add the totals: 207.2 + 64.12 + 128

The molar mass of this compound is: 399.32 g/mol


  1. Define physical and chemical properties. (4.01)

Physical properties can be observed (look, feel, etc) without altering the chemical identity of the substance. Chemical properties

  1. List three physical and three chemical properties. (4.01)

A few examples of physical properties are color, density, ductility and phase changes. A few examples of chemical properties are flammability, chemical reactivity and oxidation state.

  1. Define extensive and intensive properties. Give an example of each. (4.01)

Extensive physical properties depend on the amount of matter present in a sample of matter. An example is mass. Intensive physical properties do not depend on the amount of matter present in a sample of matter. An example is density. The density of water is 1g/mL if you have one drop or 500 gallons.

  1. When the following reaction is balanced with the lowest possible whole number coefficients, what is the coefficient in front of CO2? (4.02)

C2H4 + O2 CO2 + H2O

Let’s make a table to help us balance the equation.



Element

# Reactants

# Products

C

2

1

H

4

2

O

2

3

Since O is found in two different chemicals on the right side, I will balance that last (my personal strategy). Let’s start with C.

C2H4 + O2 2CO2 + H2O

Element

# Reactants

# Products

C

2

1 2

H

4

2

O

2

3

Now, let’s balance H’s:

C2H4 + O2 2CO2 + 2H2O

Element

# Reactants

# Products

C

2

1 2

H

4

2 4

O

2

3

Now, let’s recount our O’s as we changed the total number of O’s on the right side by placing the 2 in front of both the products:

C2H4 + O2 2CO2 + 2H2O

Element

# Reactants

# Products

C

2

1 2

H

4

2 4

O

2

3 6

Finally, let’s balance O:

C2H4 + 3O2 2CO2 + 2H2O

Element

# Reactants

# Products

C

2

1 2

H

4

2 4

O

2 3

3 6

To answer the question, the coefficient in front of CO2 when balanced, is a 2.

  1. Pick two chemicals, that when placed together would NOT produce a successful single-replacement reaction. (4.03)

A single replacement reaction is where a single element, a metal, reacts with an ionic compound. We need the activity series, which is found in the lesson. In order to write a reaction that would NOT react, the easiest way is to pick an element from the bottom to put by itself. For example: Au. Then, we can write any ionic compound that has a metal which is found higher than Au. An example: LiNO3.

So, if we write: Au + LiNO3 ? The answer is no reaction as gold, Au, is lower on the activity series. Thus, it is not reactive enough to replace lithium.

Au + LiNO3 no reaction


  1. What is the balanced equation when sulfur trioxide reacts with water? (4.04)

Sulfur trioxide is SO3. In the lesson, we learned that a nonmetal oxide reacts with water in a synthesis reaction. Basically, they just add together to form one compound (keeping things simple).

SO3 + H2O H2SO4



  1. If 4.65 moles of barium react with excess bromine gas, how many grams of barium bromide can be produced? (4.06)

Equation: Ba + Br2 BaBr2

Given/asked for: 4.65mol ? g


We are given information about one chemical, 4.65 moles Ba, and asked about another, grams BaBr2. Therefore, we need a balanced equation. This equation is already balanced (always be sure to check!)

Here is the flowchart to help:



So, we start with what we are given:

4.65 mol Ba X X = 1380 g Ba (1381.67 rounded to 3 sig figs)


  1. When 2.6 mol HCl react with 9.6 mol Mg(OH)2, what is the limiting reactant and how many moles of MgCl2 can be formed? (4.07)

unbalanced equation: Mg(OH)2 + HCl MgCl2 + H2O
Since we are switching chemicals, we must balance the equation first:

Mg(OH)2 + 2HCl MgCl2 + 2H2O


Given/asked for: 2.6 mol 9.6 mol
Since we have a specific amount of both reactants, we have a limiting reactant. We must calculate how much product each reactant could make. Whichever one produces the least amount of that product is the limiting reactant. This requires a lot of stoichiometry from lesson 4.06.
We need to setup two stoichiometry problems; each one starting with a reactant and convert to moles of MgCl2 since that is part of the question:
9.6 mol HCl X = 4.8 mol MgCl2
2.6 mol Mg(OH)2 X = 2.6 mol MgCl2
What this means is that 2.6 moles of Mg(OH)2 will produce 2.6 mol of MgCl2 and then we are out. Since Mg(OH)2 produces the least amount of product, that is the limiting reactant. The amount of the product that the limiting reactant makes is how much will form.
Limiting Reactant: Mg(OH)2

# moles of MgCl2: 2.6 moles




  1. If the reaction of 3.75 moles of lithium with excess hydrofluoric acid produced a 96.5% yield of hydrogen gas, what was the actual yield of hydrogen gas? (4.08) Unbalanced equation: Li + HF LiF + H2

We need to balance the equation first: 2Li + 2HF 2LiF + H2

This question asks for the actual yield. In order to determine that, we must start with the formula: percent yield = X 100%

We are given/asked for the following:

% yield = 95.5%

3.75 moles Li

Actual Yield = ?

Theoretical yield = ?

So, we need to use the 3.75 moles of Li and calculate how much of the product, H2, we could form. That is the theoretical yield.

3.75 mol Li X X = 3.78 g H2 (theoretical yield)

Now, we can plug & chug into the formula:

percent yield = X 100%

96.5% = X 100%

Actual yield = (0.965)(3.78 g H2)

Actual yield = 3.65 g H



Essay Topics


  1. Create a question that can be tested through science. Create a question that cannot be tested through science Explain why these can or cannot be. (1.02)

To design a question that can be tested through science, it must have a measureable basis and be able to be retested by independent groups of scientists.

Example: Which fertilizer will make my plant grow the tallest?

This is scientific as there is a clear independent variable which is type of fertilizer and a clear dependent variable which is the plant growth. Both are measureable and reproducible by others.

A question that is not scientific could include any question that asks for an opinion. An example is: What is the prettiest color flower? That is not ‘testable.’ It is a survey, not a scientific experiment. There is no independent or dependent variable.

  1. Pick one scientist (Dalton, Crookes, Thomson, Rutherford or Chadwick) and explain how the experiment led to specific changes to the model of the atom. (2.01)

You must be able to describe all the scientists and the importance of each experiment found in the lesson. Here I will explain Chadwick. He began to work with Rutherford, who had already changed the model of the atom to include the nucleus which housed the protons and the majority of the atom’s mass. Chadwick noticed that the number of protons in the nucleus was consistently less than the mass of the nucleus. There were a couple of theories that Chadwick and Rutherford devised to explain the phenomenon. Chadwick designed an experiment to test Rutherford’s belief that there was another particle in the nucleus with no charge. Chadwick was successful and discovered the nuetron’s existence and that its mass was very close to that of a proton.

  1. Write the complete balanced equation for the reaction between LiNO3 and Mg3P2. (4.02-4.05)

We have two compounds, which is indicative of a double replacement reaction. We must have mastered 3.05/3.08 in order to write our products. We need the common charges from 3.05.

LiNO3 + Mg3P2

Li is going to bond with P

Mg is going to bond with NO3 (Nitrate ion – lesson 3.08)

Notice that I wrote the metal first!

So, if Li bonds with P, we need to look up their common charges from 3.05.

Li+ P-3 How many of each ion do we need to equal zero?

Li+



Li+

+3 -3 So, it takes 3 Li’s and 1 P: Li3P

Let’s look at the other product: Mg and NO3

Mg+2 NO3-



NO3 -

+2 -2 So, it takes 1 Mg and 2 nitrates to be neutral: Mg(NO3)2

Let’s write it as one complete balanced equation:

6LiNO3 + Mg3P2 2Li3P + 3Mg(NO3)2



  1. List one of the products that forms when Mg(OH)2 decomposes (4.04)

In the lesson, we learned that decomposition occurs for many types of chemicals. We must identify the general type of chemical we have. Mg is a metal, OH is the hydroxide ion. Therefore, we have a metal hydroxide.

In the lesson, it states “metal hydroxides break down to produce a metal oxide and water”



So, we will form water and the metal oxide. Though the question didn’t ask us to write the reaction, you should be able to: Mg(OH)2 MgO + H2O

  1. Write the balanced equation for the combustion C5H12. (4.05)

This is a hydrocarbon (compound consisting of hydrogen and carbon). In the lesson, it states “When a hydrocarbon is burned completely, the products of the combustion reaction are usually carbon dioxide and water”

Looking at the examples in the lesson, you will notice that O2 is always the second reactant.

C5H12 + O2 CO2 + H2O

Now to balance: C5H12 + 8O2 5CO2 + 6H2O



  1. If 5.24 grams of sodium nitrate reacts with 6.35 grams of aluminum phosphate to produce 3.00 g of sodium phosphate, what are the theoretical yield and percent yield of this reaction? Be sure to show the work that you did to solve this problem. (4.06-4.08) unbalanced equation: NaNO3 + AlPO4 Na3PO4 + Al(NO3)3

We must balance the equation first: 3NaNO3 + 3AlPO4 Na3PO4 + Al (NO3)3

Given/Asked for: 5.24 g 6.35g 5.10g produced

Actual Yield: 3.00 g Na3PO4

Since we are given an exact amount of each reactant, we have a limiting reactant problem. We need to set up two stoichiometry problems each starting with a different reactant and converting to grams of the Na3PO4 product since that is the actual yield given in the problem.

5.24 g NaNO3 X X X = 10.11 g Na3PO4

6.35 g AlPO4 X X X = 2.85 g Na3PO4

Since the AlPO4 formed the least amount of the product, it is the limiting reactant. And, we can theoretically form a maximum of 2.85 grams of Na3PO4. Of course, when in the lab, errors are made, so we typically actually make a little less than what we should be able to. This gives rise to the “actual yield.”

Limiting reactant = AlPO4

Theoretical Yield = 2.85 grams of Na3PO4

Percent yield = ? Still have to calculate that

% yield = X 100%



% yield = X 100%

% yield = 87.7%


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