Everything Science Grade 12

CHAPTER 3. REACTION RATES 3.8

SOLUTION

1. The rate of the forward reaction will increasesince it is the forward re-
   action that is exothermic and therefore produces energy to balance the
   loss of energy from thedecrease in temperature. The rate of the reverse
   reaction will decrease.


2. The rate of the reverse and the forward reaction will increase.


3. The rate of the reverse reaction will increaseso that the extra NO gas is
   converted into NO 2 gas.

Example 7: Reaction Rates 2

QUESTION

Write a balanced equation for the exothermic reaction between Zn(s) and HCl.

Also name 3 ways to increase the reaction rate between hydrochloric acid and

zinc metal.

SOLUTION

1. Zn (s) + 2 HCl (aq)� ZnCl 2 (aq) + H 2 (g)


2. A catalyst could beadded, the zinc solid could be ground into afine
   powder to increase its surface area, the HCl concentration could be in-
   creased, or the reactiontemperature could be increased.

Exercise 3 - 6

1. The following reaction reaches equilibrium ina closed container:

CaCO 3 (s)� CaO (s) + CO 2 (g)

The pressure of the system is increased by decreasing the volume of the container.

How will the number ofmoles and the concentration of the CO 2 (g) have changed

when a new equilibriumis reached at the same temperature?