Ch. 10 & 14 gas & kinetics      test                   80 points                                  AP chemistry

In problems involving any calculation, show your work in an organized manner, include (i) any relevant equation (or formula), (ii) conversion factor(s), (iii) put the proper units in your calculations and answer, and (iv) have the proper number of significant figures in your answer.

1. 2 HCOONa + H2SO4 → 2 CO + 2 H2O + Na2SO4

A 0.964 gram sample of a mixture of sodium formate and sodium chloride is analyzed by adding sulfuric acid. The equation for the reaction for sodium formate with sulfuric acid is shown above. The carbon monoxide formed measures 242 milliliters when collected over water at 752 torr and 22.0°C. Calculate the percentage of sodium formate in the original mixture.   [15 points; HW problem]

2. At STP, 5.0 L of nitrogen gas reacts with 12.0 L of hydrogen gas to form __ grams of ammonia.  [10 points]


3. A 6.19 gram sample of PCl5 is placed in an evacuated 2.00 liter flask and is completely vaporized at 252°C.  [15 points; HW problem]

(a) Calculate the pressure in the flask if no chemical reaction were to occur.

(b) Actually at 252°C, the PCl5 is partially dissociated according to the following equation:

PCl5(g) → PCl3(g) +  Cl2(g)

The observed pressure is found to be 1.00 atmosphere. In view of this observation, calculate the
partial pressure of PCl5and PCl3in the flask at 252°C.

4. In regards to the reaction:  C2H6  +  O2  →  CO2  +  H2O,  [10 points]

a. If rate = 2.0 mM / sec, then what is    ?

b. If the rate of oxygen gas consumption is 5.0 mM / sec, what is rate of production of carbon dioxide ?

5.  2 NO(g) + 2 H2(g) → N2(g) + 2 H2O(g).  Experiments were conducted to study the rate of the reaction represented by the equation above. Initial concentrations and rates of reaction are given in the table below.  [20 points; HW problem]

expt

[NO] (M)

[H2] (M)

Rate (M / minutes)

1

.0060

.0010

1.8 * 10 -4

2

.0060

.0020

3.6 * 10 -4

3

.0010

.0060

0.30 * 10 -4

4

.0020

.0060

1.20 * 10 -4

a.  What is the rate law of the reaction.

b. The following sequence of elementary steps is a proposed mechanism for the reaction.

I. NO + NO  → N2O2
II. N2O2 + H2 → H2O + N2O
III. N2O + H2→N2+ H2O

Based on the data presented, which of the above is the rate-determining step?  Show that the mechanism is consistent with the observed rate law for the reaction.

6. Radioactive decay is described by first-order kinetics.  The half-life of 14C is 5,730 years.  A sample contains 1.0 g of 14C; how much 14C would be in the sample after 7,500 years ?  [10 points]