PreLab Quiz: Experiment 5, Le Chateliers Principle and Chemical Equilbrium

A change in pressure can shift a gaseous equilibrium system.

To determine the impact of pressure, use the

to determine the relative amount of gas in the system.

If pressure increases, the equilibrium shifts to

If pressure decreases, the equilibrium shifts to

coefficients of gases from the balanced equation

the side with fewer moles of gas

the side with more moles of gas

Consider the given gaseous system at equilibrium in a closed, rigid container.

N2O4(g)↽−−⇀2NO2(g) ΔH=+57.2 kJ

Determine how each change with shift the system to reestablish equilibrium.

Increasing temperature

Removing NO2

Decreasing the volume of the container

Adding N2O4

shift toward product side

shift toward product side

shift toward reacctant side

shift toward product side

Consider the system of copper complexes at equilibrium.

Determine how each change with shift the system to reestablish equilibrium.

Adding H2O

Adding Cu(H2O)4²+

Removing Cu(NH3)4²+

Adding HCl

No impact

shift toward product side

shift toward product side

shift toward reactant side

Consider an endothermic equilibrium system involving gases and solids in a closed, expandable container kept at constant pressure.

A(s)↽−−⇀B(g)+C(g)

Which changes will cause the equilibrium to shift?

Select one or more:

a. Increase in temperature

b. Removal of gaseous B

c. Addition of solid A

d. Addition of an inert gas

a. Increase in temperature

b. Removal of gaseous B

d. Addition of an inert gas

A change in temperature can shift an equilibrium system.

To determine the impact of temperature, use the

to determine whether the reaction is endothermic or exothermic.

If the reaction is endothermic, treat heat as a

in the equilibrium. If the reaction is exothermic, treat heat as a

in the equilibrium.

sign of the enthalpy change

reactant

product

Consider the two reactions of iron ions, one with thiocyanate (SCN−) ions and one with chloride (Cl−) ions. 

Fe3++SCN−↽−−⇀FeSCN2+

Fe3++4Cl−⟶FeCl4−

If you create an equilibrium mixture from Fe3+ and SCN− ions, adding Cl− ions will  remove the Fe3+ from the equilibrium mixture and will cause the reaction to

proceed in the reverse direction

According to Le Châtelier's Principle, heat applied to an exothermic reaction will shift the reaction towards

Heat applied to an endothermic reaction will shift the reaction towards

the reactants

the products

Review the reversible reactions given, along with the associated equilibrium constant K at room temperature. In each case, determine whether the products or reactants are favored.

• AgCl↽−−⇀Ag++Cl−Ksp=1.6×10−10

• A+B↽−−⇀CK=4.9×103

• Al(OH)3↽⇀Al3++3OH−Ksp=3.7×10−15

• CH3COOH↽⇀CH3COO+H+Ka=1.8×10−5

reactants

products

reactants

reactants

Fill in the expression for the equilibrium constant K for the reaction given.

A(aq)+2B(aq)↽−−⇀2C(aq)+D(aq)

K= 

C²D/B²A