equilibrium

Question 1

Kc equation

Answer 1

Kc= [C]c + [D]d
—————-
[A]a + [B]b.

Question 2

units for Kc

Answer 2

Kc = (moldm-3)(moldm-3)
——————————
(moldm-3)2(moldm-3)2. =. mold-2dm6

Question 3

example: CrO4 2- -> Cr2O7 2-

Answer 3

as acid is added, the position of equilibrium shifts to the right, causing the orange dichromate (VI) ion, Cr2O7 to dominate. However in alkaline conditions, the position of equilibrium shifts to the left and the yellow chromate (VI) ion, CrO4 ion dominates. In each case, the value of Kc remains constant on the addition of acid or alkaline however the amount of each ion adjusts to esablish a new equilibrium, which is described ny Kc.

Question 4

effects of temperature on Kc

Answer 4

A high Kc value would indicate that the position of the equilibrium lies to the RHS. A low Kc value would indicate that the position of equilibrium lies to the left hand side. the higher the Kc value then the further the position of equilibrium is to the right

Question 5

exothermic reaction

Answer 5

A + B <=> C + D + heat

Question 6

endothermic reactions

Answer 6

A+ B + heat <=> C + D

Question 7

what is the only factor that influences kc

Answer 7

Temperature

Question 8

example; The formation of ammonium carbonate is being investigated as a possible method to
remove carbon dioxide from combustion processes.
CO2 + 2NH3 + H2O ⇌ (NH4)2CO3
The equilibrium constant for the reaction at 20oC is 2.5 x 104. At 80oC the
equilibrium constant is 0.12. Explain the drop in the value of K and state how this
would affect the CO2 removal process

Answer 8

Increasing the temperature from 20 oC to 80 oC shows a decrease in the value of Kc.
The lower Kc value at the higher temperature suggests that the equilibrium shifts to
the left hand side and that the reverse reaction is favoured; which would in turn suggest
that the reaction is exothermic. Increasing the temperature would cause a decrease
in the removal of CO2 in this combustion process.