Unit 5 Study Guide

• A Graph 1, because the rate of O2 consumption is half the rate at which NO is consumed; two molecules of NO react for each molecule of O2 that reacts.

• B Graph 1, because O2 molecules are consumed at a slower rate at the beginning of the reaction when there are not as many molecules of NO2 produced.

• C Graph 2, because there is a large excess of O2 molecules and its concentration will not change drastically over time.

• D Graph 2, because a collision between three molecules to form a product has a low probability and the concentration of O2 will remain relatively constant.

• A The rate of formation of CO2(g) will be the same because the mass of CaCO3(s)

  and the volume of HCl(aq) used will be the same in both experiments.

• B The rate of formation of CO2(g) will be the same because the surface area of the solid

  and the average kinetic energy of the particles will be the same in both experiments.

• C CO2(g) will be formed at a faster rate in experiment 2 because more H+ particles can

  react per unit time.

• D CO2(g) will be formed at a faster rate in experiment 1 because the proportion of

  CaCO3(s) particles to H+ particles will be greater.

When the chemical reaction 2NO(g) + O2(g) → 2NO2(g) is carried out under certain conditions, the rate of disappearance of NO(g) is 5.0×10−5Ms−1. What is the rate of disappearance of O2(g) under the same conditions?

• A Because two molecules of NO are consumed per molecule of O2 , the rate of disappearance of O2(g) is 2.5 × 10−5Ms−1 .

• B Because two molecules of NO are consumed per molecule of O2 , the rate of disappearance of O2(g) is 1.0 × 10−4Ms−1 .

• C Because the rate depends on [NO]2 and [O2] , the rate of disappearance of O2(g) is 2.5 × 10−9Ms−1 .

• D Because the O2(g) is under the same experimental conditions as NO , it is consumed at the same rate of 5.0 × 10−5Ms−1 .

C2H4(g) + H2(g) ----->C2H6(g)

Which of the following will most likely increase the rate of the reaction represented above?

• A Decreasing the temperature of the reaction system

• B Adding a heterogeneous catalyst to the reaction system

• C Increasing the volume of the reaction vessel using a piston

• D Removing some H2(g) from the reaction system

C2H4(g) + H2(g) ---->C2H6(g)C2

H4(g) is reduced by H2(g) in the presence of a solid platinum catalyst, as represented by the

equation above.

Factors that could affect the rate of the reaction include which of the following?

I Changes in the partial pressure of H2(g)

II Changes in the particle size of the platinum catalyst

III Changes in the temperature of the reaction system

• A III only

• B I and II only

• C I and III only

• D II and III only

• E I , II and III

5 H2O2(aq) + 2 MnO4-(aq) + 6 H+(aq) → 2 Mn2+(aq) + 8 H2O(l)+ 5 O2(g)

In a titration experiment, H2O2(aq) reacts with aqueous MnO4-(aq) as represented by theequation above. The dark purple KMnO4solution is added from a buret to acolorless, acidified solution of H2 O2(aq) in an Erlenmeyer flask. At a certain time during the titration, the rate of appearance of O2(g) was1.0 x 10-3 mol L-1 s-1 . What was the rate of disappearance of MnO4- at the same time?

• A 6.0 x 10-3 mol L-1 s-1

• B 4.0 x 10-3 mol L-1 s-1

• C 6.0 x 10-4 mol L-1 s-1

• D 4.0 x 10-4 mol L-1 s-1

A kinetics experiment is set up to collect the gas that is generated when a sample of chalk, consisting primarily of solid CaCO3 , is added to a solution of ethanoic acid, CH3 COOH. The rate of reaction between CaCO3 and CH3 COOH is determined by measuring the volume of gas generated at 22 °C and 1 atm as a function of time. Which of the following experimental conditions is most likely to increase the rate of gas production?

• A Decreasing the volume of ethanoic acid solution used in the experiment

• B Decreasing the concentration of the ethanoic acid solution used in the experiment

• C Decreasing the temperature at which the experiment is performed

• D Decreasing the particle size of the CaCO3 by grinding it into a fine powder

A 0.35 g sample of Li(s) is placed in an Erlenmeyer flask containing 100 mL of water at 25 °C. A balloon is placed over the mouth of the flask to collect the hydrogen gas that is generated. Which of the following changes will most likely increase the rate of reaction between Li(s) and water?

• A Using 125 mL of water instead of 100 mL

• B Using a 0.25 g sample of Li(s) instead of a 0.35 g sample

• C Using a 0.35 g sample of Li(s) cut into small pieces

• D Decreasing the water temperature before adding the Li(s)

Relatively slow rates of chemical reaction are associated with which of the following?

• A The presence of a catalyst

• B High temperature

• C High concentration of reactants

• D Strong bonds in reactant molecules

• E Low activation energy

• A The reaction in Figure 1, because the atoms of Mg are more concentrated than those

  in Figure 2

• B The reaction in Figure 1, because the Mg(s) in Figure 1 has a larger mass than the

  Mg(s) in Figure 2

• C The reaction in Figure 2, because more Mg atoms are more exposed to HCI(aq) in

  Figure 2 than in Figure 1

• D The reaction in Figure 2, because the Mg(s) in Figure 2 has less surface area than the

  Mg(s) in Figure 1