Practice Chemical Equilibrium in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

A dynamic state in a reversible reaction where the forward and reverse reactions proceed at equal rates, so the macroscopic concentrations of reactants and products stay constant even though molecules keep converting in both directions.

The reaction is still happening both ways, but the amounts stay constant.

Showing a random 20 of 76 problems.

Example 1

easy
Does adding a catalyst shift the equilibrium position?

Example 2

easy
For H2(g)+I2(g)⇌2HI(g), at equilibrium [H2]=0.10 M, [I2]=0.10 M, and [HI]=0.80 M. Compute Kc.

Example 3

medium
For the reaction N2+3H2⇌2NH3, at equilibrium [N2]=0.50 M, [H2]=1.50 M, and [NH3]=0.60 M. Calculate Keq.

Example 4

hard
For an endothermic reaction at equilibrium, predict the effect on K of (a) raising T, (b) adding an inert gas at constant volume.

Example 5

easy
At chemical equilibrium, what is true about the forward and reverse reaction rates?

Example 6

medium
For PCl5(g)⇌PCl3(g)+Cl2(g), Kc=0.040 at T. If [PCl5]=0.10 M, [PCl3]=0.20 M, [Cl2]=0.10 M, compute Q and predict the shift direction.

Example 7

challenge
For H2+I2⇌2HI, K=50. If [H2]0=[I2]0=1.00 M, no HI initially, find [HI] at equilibrium.

Example 8

medium
For 2SO2+O2⇌2SO3, at equilibrium [SO2]=0.20, [O2]=0.50, [SO3]=0.40 M. Find K.

Example 9

medium
For A⇌B with K=0.01, are reactants or products favored, and by roughly how much?

Example 10

hard
Reaction 1: A⇌B has K1=2. Reaction 2: B⇌C has K2=3. Find K for A⇌C.

Example 11

medium
For N2O4⇌2NO2, K=0.211 at equilibrium [N2O4]=0.500 M. Find [NO2].

Example 12

medium
At equilibrium in a reversible reaction, have the reactions stopped? Explain what is equal at equilibrium.

Example 13

challenge
Reaction X⇌Y has K=9 at 300 K and K=4 at 400 K. Is the forward reaction exothermic or endothermic? Explain.

Example 14

easy
If K≫1 for a reaction at equilibrium, are products or reactants favored?

Example 15

easy
Which direction does CO(g)+H2O(g)⇌CO2(g)+H2(g) shift if H2 is removed?

Example 16

hard
Reaction X⇌Y has K=16 at 25∘C and K=4 at 80∘C. Is the forward reaction exothermic or endothermic?

Example 17

hard
Kc for N2+3H2⇌2NH3 is 0.50 at T. Compute Kc for 12N2+32H2⇌NH3.

Example 18

medium
Acetic acid dissociates as HC2H3O2⇌H++C2H3O2− with Ka=1.8×10−5. Find [H+] in a 0.10 M solution.

Example 19

hard
Kp for N2+3H2⇌2NH3 at T=500 K is 1.5×10−5 atm−2. Convert to Kc. Use R=0.0821 L atm/(mol K).

Example 20

hard
If Kc=4.0 for A+B⇌C+D, what is Kc for the reverse reaction C+D⇌A+B?
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