Chemistry Test Chemical Equilibrium

Question 1

What is the correct definition of chemical equilibrium in a reversible reaction?

Accepted Answer

The rates of the forward and reverse reactions are equal

Answer

At chemical equilibrium, the forward and reverse reactions proceed at the same rate, so the net concentrations of reactants and products remain constant.

Question 2

Which expression correctly represents the equilibrium constant Kc for the reaction: N₂(g) + 3H₂(g) ⇌ 2NH₃(g)?

Accepted Answer

Kc = [NH₃]² / ([N₂][H₂]³)

Answer

Kc is expressed as products over reactants, each raised to the power of their stoichiometric coefficients: [NH₃]² / ([N₂]¹[H₂]³).

Question 3

If Kc >> 1 for a reaction, what does this indicate about the equilibrium position?

Accepted Answer

The equilibrium strongly favors the products

Answer

A large Kc (>> 1) means the numerator (products) dominates the expression, so the equilibrium lies far to the right, favoring product formation.

Question 4

For the reaction H₂(g) + I₂(g) ⇌ 2HI(g), if [H₂] = 0.5 M, [I₂] = 0.5 M, and [HI] = 2.0 M at equilibrium, what is Kc?

Accepted Answer

16

Answer

Kc = [HI]² / ([H₂][I₂]) = (2.0)² / (0.5 × 0.5) = 4.0 / 0.25 = 16.

Question 5

What is the relationship between Kp and Kc for a gas-phase reaction?

Accepted Answer

Kp = Kc(RT)^Δn

Answer

Kp = Kc(RT)^Δn, where Δn is the change in moles of gas (moles of gaseous products minus moles of gaseous reactants), R is the gas constant, and T is temperature in Kelvin.

Chemistry Practice Test Practice Test

Chemistry Practice Test Practice Test

Chemistry Test Chemical Equilibrium