Everything Science Grade 12

CHAPTER 3. REACTION RATES 3.8

(a) decrease the concentration of B

(b) decrease the temperature of A

(c) grind A into a fine powder

(d) decrease the pressure

(IEB Paper 2, 2002)

5. Gases X and Y are pumped into a 2 dm^3 container. When the container is sealed,
   4 moles of gas X and 4moles of gas Y are present. The following equilibrium is
   established:

2 X (g) + 3Y (g)� X 2 Y 3

The graph below shows the number of molesof gas X and gas X 2 Y 3 that are

present from the time the container is sealed.

30

time (s)

0,5

4

number

(^70100)
moles
of
(a) How many moles ofgas X 2 Y 3 are formed by the timethe reaction reaches
equilibrium at 30 seconds?
(b) Calculate the valueof the equilibrium constant at t = 50 s.
(c) At 70 s the temperature is increased. Is theforward reaction endothermic
or exothermic? Explainin terms of Le Chatelier’s Principle.
(d) How will this increase in temperature affect the value of the equilibrium
constant?
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