# Question 13.1: Writing Equilibrium Equations for Gas-Phase Reactions Write ......

Writing Equilibrium Equations for Gas-Phase Reactions

Write the equilibrium equation for each of the following reactions:

(a) $N_2$(g) + 3 $H_2$(g) $\rightleftharpoons$ 2 $NH_3$(g)

(b) 2 $NH_3$(g) $\rightleftharpoons$ $N_2$(g) + 3 $H_2$(g)

STRATEGY

Put the concentrations of the reaction products in the numerator of the equilibrium-constant expression and the concentrations of the reactants in the denominator. Then raise the concentration of each substance to the power of its coefficient in the balanced chemical equation.

Step-by-Step
The 'Blue Check Mark' means that this solution was answered by an expert.
$\text { (a) } K_{\mathrm{c}}=\frac{\left[\mathrm{NH}_3\right]^{2 \ \leftarrow \ Coefficient \ of \ NH_3}}{\left[\mathrm{~N}_2\right]\left[\mathrm{H}_2\right]^{3 \ \leftarrow \ Coefficient \ of \ H_2}}$

(b) $K_{\mathrm{c}}{ }^{\prime}=\frac{\left[\mathrm{N}_2\right]\left[\mathrm{H}_2\right]^{3 \ \leftarrow \ Coefficient \ of \ H_2}}{\left[\mathrm{NH}_3\right]^{2 \ \leftarrow \ Coefficient \ of \ NH_3}} \ \ \ \ \ \ \ \ K_c{ }^{\prime}=\frac{1}{K_c}$

Because the balanced equation in part (b) is the reverse of that in part (a), the equilibrium-constant expression in part (b) is the reciprocal of the expression in part (a) and the equilibrium constant $K_{c}^{ʹ}$ is the reciprocal of $K_c$

Question: 13.6

## Determining the Equilibrium Constant Kp Methane (CH4) reacts with hydrogen sulfide to yield H2 and carbon disulfide, a solvent used in manufacturing rayon and cellophane: CH4(g) + 2 H2S(g) ⇔ CS2(g) + 4 H2(g) What is the value of Kp at 1000 K if the partial pressures in an equilibrium mixture at ...

K_{\mathrm{p}}=\frac{\left(P_{\mathrm{CS}_2...
Question: 13.16

## Applying Le Châtelier’s Principle to Temperature Changes The following pictures represent the composition of the equilibrium mixture at 600 K and 650 K for the combination of two A molecules, 2 A(g) ⇔ A2(g): Is the reaction endothermic or exothermic? Explain using Le Châtelier’s principle. ...

Two A and five $A_2$ molecules are pr...
Question: 13.15

## Applying Le Châtelier’s Principle to Temperature Changes In the first step of the Ostwald process for the synthesis of nitric acid, ammonia is oxidized to nitric oxide by the reaction 4 NH3(g) + 5 O2(g) ⇔ 4 NO(g) + 6 H2O(g) ΔH°  = -901.2 kJ How does the equilibrium amount of NO vary with an ...

Because the oxidation of ammonia is exothermic, we...
Question: 13.14

## Applying Le Châtelier’s Principle to Pressure and Volume Changes Does the number of moles of reaction products increase, decrease, or remain the same when each of the following equilibria is subjected to a decrease in pressure by increasing the volume? (a) PCl5(g) ⇔ PCl3(g) + Cl2(g) ...

(a) Because the forward reaction converts 1 mol of...
Question: 13.13

## Applying Le Châtelier’s Principle to Concentration Changes The reaction of iron(III) oxide with carbon monoxide occurs in a blast furnace when iron ore is reduced to iron metal: Fe2O3(s) + 3 CO(g) ⇔ 2 Fe(l) + 3 CO2(g) Use Le Châtelier’s principle to predict the direction of the net reaction when ...

(a) Because $Fe_2O_3$ is a pure solid...
Question: 13.12

## Calculating Equilibrium Partial Pressures from Initial Partial Pressures One reaction that occurs in producing steel from iron ore is the reduction of iron(II) oxide by carbon monoxide to give iron metal and carbon dioxide. The equilibrium constant Kp for the reaction at 1000 K is 0.259. ...

Step 1 The balanced equation is \mathrm{FeO...
Question: 13.11

## Calculating Equilibrium Concentrations from Unequal Initial Concentrations Calculate the equilibrium concentrations of H2, I2, and HI at 700 K if the initial concentrations are [H2] = 0.100 M and [I2] = 0.200 M. The equilibrium constant Kc for the reaction H2(g) + I2(g) ⇔ 2 HI(g) is 57.0 at 700 K. ...

Step 1 The balanced equation is \mathrm{H}_...
Question: 13.10

## Calculating Equilibrium Concentrations from Equal Initial Concentrations The equilibrium constant Kc for the reaction of H2 with I2 is 57.0 at 700 K: H2(g) + I2(g) → 2 HI(g) Kc = 57.0 at 700 K If 1.00 mol of H2 is allowed to react with 1.00 mol of I2 in a 10.0 L reaction vessel at 700 K, what are ...

Step 1 The balanced equation is given: \mat...
Question: 13.9

## Predicting the Direction of Reaction A mixture of 1.57 mol of N2, 1.92 mol of H2, and 8.13 mol of NH3 is introduced into a 20.0 L reaction vessel at 500 K. At this temperature, the equilibrium constant Kc for the reaction N2(g) + 3 H2(g) ⇔ 2 NH3(g) is 1.7 × 10² . Is the reaction mixture at ...

The initial concentration of $N_2$ is...
(a) K_{\mathrm{c}}=\frac{[\mathrm{CO}]^2}{\...