Chemistry Team Test Answers
9th Annual FGCU Invitational Mathematics Competition
December 8, 2011
__________________________________________________________________________
1. The reaction A → B is first order in [A]. Consider the following data.
The rate constant for this reaction is __________
.
Answer: 0.071 s-1, 0.069 s-1, or 0.084 s-1 depending which data points the students use to calculate k using
the formula ln [At / A0] = - kt
2. Calculate the pH of a buffer formed by mixing 65 mL of 0.20 M NaHCO3 with 75 mL of 0.15 M
Na2CO3. For H2CO3; Ka1= 4.46 ×10-7;
Ka2 = 4.69×10-11
Answer is 10.27.
3. The formula of a salt is XSO4. The X-ion in this salt has 39 electrons. The metal X is __________.
Answer: Nb
4. The volume of fluorine gas required to react with 4.26 g of calcium bromide to form calcium fluoride and
bromine at 25.0°C and 4195 torr is __________ L.
Answer: 0.0945 L
5. What volume (mL) of a concentrated solution of magnesium chloride (9.00 M) must be diluted to 350. mL
to make a 2.75 M solution of magnesium chloride?
Answer: 107 mL
Diff: 2
Page Ref: Sec. 4.5
6. The combustion of ammonia in the presence of oxygen yields NO2 and H2O:
NH3 (g) + O2 (g) →
NO2 (g) + H2O (g) (not balanced)
The combustion of 43.9 g of ammonia with 258 g of oxygen produces __________ g of NO2.
Answer: 119 g NO2
7. The pressure of a sample of CH4 gas (6.022 g) in a 30.0 L vessel at 402 K is __________ atm.
Answer: 0.413 atm
Diff: 3
Page Ref: Sec. 10.4
8. Rank the compounds in order of lowest boiling point to highest boiling point.
H2S
NH3
HCl
CH4
Answer: CH4 < H2S < HCl < NH3
9. In a titration of 35.00 mL of 0.737 M H2SO4, __________ mL of a 0.827 M KOH solution is required for
neutralization.
Answer: 62.4 mL
Diff: 3
Page Ref: Sec. 4.6
10. The data in the table below were obtained for the reaction:
A + B → P
The rate law for this reaction is rate = __________.
Answer: k[A]2
11. Propane (C3H8) reacts with oxygen in the air to produce carbon dioxide and water. In a particular
experiment, 38.0 grams of carbon dioxide are produced from the reaction of 22.05 grams of propane with
excess oxygen. What is the percent yield in this reaction?
Answer: 57.6
12. HZ is a weak acid. An aqueous solution of HZ is prepared by dissolving 0.020 mol of HZ in sufficient
water to yield 1.0 L of solution. The pH of the solution was 4.93 at 25.0°C. At 25.0°C, what is the Ka of
HZ is __________.
Answer: 6.9 × 10-9
Diff: 4
Page Ref: Sec. 16.6