Chemistry 111
Practice EXAM 1B
NAME: __________________________
SECTION #: ______________
1. ______How many significant figures are in 0.01020?
(a) 2
(c) 4
(b) 3
(d) 5
2. ______An example of a chemical property is:
(a) Color
(c) Melting point
(b) Flammability
(d) Density
3. ______Which of the following forms of radiation would be attracted to a
positively charged plate?
(a) α particle
(c) γ particle
(b) β particle
(d) none of these choices
4. ______How many neutrons are in the following isotope: 131I ?
(a) 53
(c) 127
(b) 78
(d) 131
5. ______Which of the following is the correct formula for potassium nitrate?
(a) KNO3
(c) KNO2
(b) K3N
(d) KCN
6. ______The sodium atom typically loses 1 electron to become:
(a) A larger sodium anion
(c) A larger sodium cation
(b) A smaller sodium anion
(d) A smaller sodium cation
7. ______Sodium azide, a shock-sensitive solid, is commonly used in automobile air
bags because of its ability to rapidly release N2 gas according to the following
unbalanced equation: NaN3(s) → Na(s) + N2(g)
How much N2 will be produced if 84.5 g of 93.7% pure NaN3 reacts completely:
(a) 24.3 g
(c) 51.2 g
(b) 34.1 g
(d) 79.2 g
8. ______How many grams of carbon dioxide are generated in the combustion of
43.0 g of hexane (C6H14(l)) in air?
(a) 63.0 g
(c) 216 g
(b) 132 g
(d) 301 g
9. ______If 3.62 g of hydrogen gas reacts with 7.01 g of nitrogen gas to form
ammonia gas, what is the limiting reagent?
(a) Hydrogen gas
(c) Ammonia gas
(b) Nitrogen gas
(d) Water vapor
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10. ______What is the percent yield of a reaction in which 19.78 g of NiCO3
produces 11.6 g of NiO?
(a) 58.6%
(c) 93.2%
(b) 78.3%
(d) 98.9%
11. ______Which of the following would not dissolve in water?
(a) Li3PO4
(c) CuCl2
(d) SrSO4
(b) Pb(NO3)2
12. ______What is the percentage by mass of copper in copper (II) sulfate?
(a) 39.8%
(c) 57.0%
(b) 43.6%
(d) 66.4%
13. ______Hydrogen will be displaced from cold water by all of the following except:
(a) Li
(c) Na
(b) Sn
(d) K
14. ______Choose the most appropriate definition for equivalence point from below:
(a) The point when you have used all of the solution in your burette and must
now refill with standard solution.
(b) The point at which you have stoichiometrically equivalent quantities of
reactants.
(c) The point at which you are ready to add the indicator to the solution you
are titrating.
(d) The point at which the eriochrome black T exhibited a bright yellow tinge
in the analysis of bottled water samples.
15. _______What was the gas given off during the reaction of your seltzer tablet?
(a) Carbon dioxide
(c) Hydrogen
(b) Oxygen
(d) Sulfur trioxide
Part 2 (40 pts total). Partial credit may be given where appropriate. Show all work.
16. Caffeine, a stimulant commonly found in coffee, tea, and chocolate, contains (by
mass) 49.48% C, 5.15% H, and 28.87% N, with the balance being oxygen.
(a) Find the empirical formula of caffeine. (6 pts)
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(b) If there are 4 N atoms in each caffeine molecule, what is the molar mass of
caffeine? (3 pts)
(c) If your 100. g chocolate bar is 0.24% caffeine by mass, how many
caffeine molecules are present in this bar? (4 pts)
17. For the following reaction:
Ba(OH)2(aq) + HClO2(aq) → Ba(ClO2)2(aq) + H2O(l)
(a) Name each reactant and product from above. (2 pts)
(b) Write a balanced complete ionic equation. (2 pts)
(c) Write a balanced net ionic equation. (2 pts)
(d) If 7.15 g of Ba(OH)2 is added to sufficient water to yield 125 mL of
solution, what is the minimum amount, in L, of 0.21 M HClO2 that must
be added to neutralize the Ba(OH)2? (4 pts)
(e) If phenolphthalein is added to the Ba(OH)2 solution prepared in Part (d)
above and this solution is then titrated with HClO2, how will you know
when the neutralization is complete (be explicit!)? (2 pts)
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