## Chemistry (4th Edition)

Published by McGraw-Hill Publishing Company

# Chapter 15 - Questions and Problems - Page 709: 15.39

#### Answer

When the mixture reaches equilibrium, the total pressure is less than the sum of the initial pressures.

#### Work Step by Step

1. Write the equilibrium constant expression: - The exponent of each concentration is equal to its balance coefficient. $$K_p = \frac{[Products]}{[Reactants]} = \frac{[ SO_3 ]^{ 2 }}{[ SO_2 ]^{ 2 }[ O_2 ]}$$ 2. At equilibrium, these are the concentrations of each compound: $[ SO_2 ] = 0.350 \space - 2x$ $[ O_2 ] = 0.762 \space - x$ $[ SO_3 ] = 2x$ $$5.60 \times 10^{4} = \frac{(2x)^2}{(0.350-2x)^2(0.350-2x)}$$ x = 0.169 $[ SO_2 ] = 0.350 \space - 2(0.169) = 0.012$ $[ O_2 ] = 0.762 \space - 0.169 = 0.059$ $[ SO_3 ] = 2(0.169) = 0.338$ 3. Total initial pressure = 0.350 + 0.762 + 0 = 1.112 atm 4. Total equilibrium pressure = 0.012 + 0.059 + 0.338 = 0.409 atm

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