CHEMISTRY 101Name ______
Hour Exam II
October 28, 2008Signature ______
Adams/Denofrio
Section ______
"Try not to become a person of success but rather try to become a person of value."
--Albert Einstein (Adapted)
This exam contains 17 questions on 7 numbered pages. Check now to make sure you have a complete exam. You have one hour and fifteen minutes to complete the exam. Determine the best answer to the first 15 questions and enter these on the special answer sheet. Also, circle your responses in this exam booklet. Show all of your work and provide complete answers to questions 16 and 17.
1-15(30 pts.)______
16 (14 pts.)______
17 (16 pts.)______
Total (60 pts)______
Useful Information:
1.000 L = 1000.0 mL
Always assume ideal behavior for gases (unless explicitly told otherwise).
PV = nRT
R = 0.08206 L·atm/mol·K
K = C + 273
NA = 6.022 x 1023
Solubility Rules:
1. Most nitrate salts are soluble.
2. Most salts of sodium, potassium, and ammonium cations are soluble.
3. Most chloride salts are soluble. Exceptions: silver(I), lead(II), and mercury(I) chloride.
4. Most sulfate salts are soluble. Exceptions: calcium, barium, and lead(II) sulfate.
5. Most hydroxide salts can be considered insoluble. Soluble ones: sodium, potassium, and calcium hydroxide.
6. Consider sulfide, carbonate, and phosphate salts to be insoluble. Soluble ones: sodium and potassium.
CHEMISTRY 101Fall 2008
Hour Exam IIPage No. 1
1.Which of the following most accurately describes a spectator ion?
a)An ion that is used up in a chemical reaction; it is limiting.
b)An ion that participates in a chemical reaction but is always present in excess.
c)An ion that becomes part of the precipitate in a chemical reaction.
d)An ion that does not have a charge but can dissolve in solution and thus does not conduct electricity.
e)An ion that is present in solution but does not participate directly in the chemical reaction.
2.Recall the “pop bottle” demonstration where hydrogen and oxygen gases react to form water. Which of the following statements is false concerning this chemical reaction?
a)In order for this reaction to occur, the hydrogen bonds and oxygen bonds must break and reform into O–H bonds to make water.
b)The chemical reaction will make the most noise when using a 2:1 mole mixture of hydrogen to oxygen gases.
c)The same numbers of molecules on the reactant side must appear on the product side in order to follow the law of conservation of matter.
d)The total mass that is present before the reaction takes place must be accounted for after the reaction occurs.
e)The flame of the Bunsen burner does not act as a source of hydrogen and oxygen gases to make the water, it only gets the reaction going.
3.Elemental phosphorus burns in oxygen with an intensely hot flame, producing a brilliant light and clouds of the oxide product.
If 6.25 g of phosphorus is burned, what mass of oxygen does it combine with?
a)0.252 gb)0.323 gc)4.04 gd)8.07 ge)32.3 g
4. You add 300.0 mL of water to 300.0 mL of a 2.00 M sugar solution. How many of the following will change?
I.total volume of the solution
II.moles of solute in the solution
III.mass of solute in the solution
IV.concentration of the solution
V.number of solute molecules in the solution
a)1b)2c)3d)4e)5
5. Consider the following unbalanced equation:
Which of the following best represents the equation balanced in standard form?
a)
b)
c)
d)
e)
6.Consider 1.00 L of 1.00 M potassium chloride with 1.00 L of 1.00 M sodium nitrate. After the solutions are mixed and allowed to react, will the final solution conduct electricity (light up a light bulb like in lecture)? Choose the best answer.
a)Yes. Not all of the ions will be used up to make the precipitate, therefore some will be left in solution and will conduct electricity.
b)Yes. All of the ions are soluble and will remain in solution when mixed and can therefore conduct electricity.
c)No. Both reactants will be completely used up to make the precipitate, so no ions will be left to conduct electricity.
d)No. None of these compounds are soluble in water, therefore they do not even break up into ions in solution and thus they cannot conduct electricity.
e)No. Even though these compounds dissolve in water, they are not charged and thus cannot conduct electricity.
7.Consider the following reaction:
If 15.00 g of solid zinc reacts with 100.0 mL of 4.00 M hydrochloric acid, what volume of hydrogen gas is produced at 25°C and 1.00 atm?
a)4.89 Lb)0.200Lc)19.6 Ld)9.78 Le)5.61 L
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Use the following scenario to answer questions8 – 10.
Consider the following reaction between 150.0 mL of 0.10 M Na2CrO4 and 100.0 mL of
0.10 M AgNO3. A red precipitate forms.
8.Which of the following microscopic drawings best represents what is in solution after the reaction is complete?
a) b) c)
d) e)
9. What mass of precipitate will form?
a)0.0050 gb)0.010 gc)1.7 gd)3.3 ge)6.6 g
10. What is the concentration of sodium ions left in solution after the reaction is complete?
a)0.030Mb)0.10 Mc)0.12 Md)0.20 Me)0.060M
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11.What volume of a 10.0 M stock solution of sodium dichromate would you need to make 250.0 mL of a 3.5 M solution?
a)88 mLb)11 mLc)250 mLd)163 mLe)714 mL
12.Consider separate solutions of NaCl, CaCl2, and AuCl3 made by dissolving equal masses of each solute in equal volumes of solution. Which solution has the greatest concentration of chloride ions?
a)NaCl
b)CaCl2
c)AuCl3
d)At least two of the above solutions have the same greatest concentration of chloride ions.
e)Not enough information is given to solve this problem.
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Use the following scenario to answer questions13 – 14.
Consider the reaction for lighting a match:
13.If 3.50 moles of P2O5 were produced in this reaction, how many moles of KCl were produced?
a)1.75 molb)2.10 molc)3.50 mold)5.83 mole)435 mol
14.If 3.50 moles of P2O5 were produced in this reaction, how many moles of P4 were required?
a)1.75 molb)3.50 molc)5.83 mold)7.00 mole)217 mol
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15.Recall from lab where you mixed two different acids with sodium hydroxide and measured the temperature change for various amounts added. The larger the temperature change, the more products formed. For the reaction of sulfuric acid with sodium hydroxide, which trial would show the greatest temperature change?
mol Acid / mol BaseTrial 1 / 5.00 / 10.0
Trial 2 / 5.00 / 5.00
Trial 3 / 10.0 / 20.0
Trial 4 / 10.0 / 30.0
a)Trial 1
b)Trial 2
c)Trial 3
d)Trial 4
e)At least two trials would show the same greatest temperature change.
16.10.0 g of sodium metal reacts with 2.50 L of nitrogen gas at 0.976 atm and 28°C, to produce sodium nitride.
Answer each question below thoroughly. Show all of your work in an organized manner in the space provided.
a.Write the balanced chemical equation in standard form for this reaction. Do not include phases.
b.How many grams of sodium nitride are produced in this reaction?
c.Prove that mass has been conserved (within two significant figures).
17.The following are true/false statements that require explanation. State whether each are “true” or “false” and then provide the requested explanation or support. Please limit your answers to the space provided.
True or False?For the following unbalanced reaction: , a coefficient of “10” in front of oxygen can be used to balance the equation. Whether true or false, provide a thorough explanation along with a correctly balanced equation.
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Consider a solution with the following ions present:
.
True or False?When all are allowed to react (and there is plenty available of each), exactly three different solids will form. Whether true or false, list all of the solids that will form using the correct formulas in your explanation.
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True or False?The limiting reactant is always the reactant that has the smallest molar
mass. If true, explain why. If false, explain why along with a counterexample.
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Consider the following scenario: You create 900. mL of solution by dissolving 50.0 g of
potassium sulfate in water. You leave the solution uncovered for a week and find that 300. mL of water evaporated.
True or False?The concentration of the solution will remain the same over this period of time. Whether true or false, explain why and include the actual concentration of the final solution. (Show all work.)