The equilibrium constant

Question 1

a homogeneous system is a system in which

Answer 1

all components are in the same phase (state)

Question 2

a heterogeneous system is where

Answer 2

at least two different phases are present

Question 3

Kc = (what does it represent)

Answer 3

the equilibrium constant

Question 4

Kc=

Answer 4

Kc= ([C]c x [D]d) / ([A]a x [B]b)

Question 5

we represent equilibrium reactions as:

Answer 5

aA +bB ⇌ cC + dD

Question 6

the equilibrium law equation for the equilibrium constant is:

Answer 6

[C]c x [D]d
Kc= ________
[A]a x [B]b

When aA + bB ⇌ cC + dD

Question 7

the equilibrium constant is measure in

Answer 7

concentration, which changes depending on the order of reaction

Question 8

the value of Kc depends on : (2 items)

Answer 8

• temperature
• the reaction as written

-it DOES NOT depend on the pressure or te presence of a catalyst

Question 9

for heterogeneous reactions, the………..is omitted from the equation because………………………………..

Answer 9

the solid is omitted because it is assumed that the concentration of a pure solid is constant. we can assume this because solids are incompressible

Question 10

write the equilibrium constant for the following reaction:
CaCO3(s) ⇌ CaO(s) + CO2(g)

Kc=

Answer 10

Kc= [CO2]

The CaCO3 and the CaO are solid, so constant and therefore omitted form the equation

Question 11

the three rules for [H2O] in equilibrium expressions are:

Answer 11

• when water is in the GASEOUS state, [H2O] MUST ALWAYS appear in the equilibrium constant expression
• when water is a reactant but NOT the solvent, the term [H2O] MUST ALWAYS appear in the equilibrium constant expression
• hen water is the SOLVENT, even if it is also a reactant or product, [H2O] does NOT appear in the expression for the equilibrium constant

Question 12

we can use the equilibrium constant expression to predict the effect of concentration on the equilibrium position.
so, if we increase the concentration of NO2, then what will happen to the equilibrium position on this reaction:
(use the expression!)
2NO2(g) ⇌ N2O4(g)

Answer 12

• Kc= [N2O4] / [NO2]²
• if NO2 is increased, then the equation’s value will greatly decrease
• this means the expression’s value is less than that of Kc
• in order for the values to be equal, the concentration of N2O4 must increase so that the expression’s values is increase to equal Kc, so the equilibrium must shift right in order for the concentration of N2O4 to increase