General Chemistry: Principles and Modern Applications (10th Edition)

Published by Pearson Prentice Hal
ISBN 10: 0132064529
ISBN 13: 978-0-13206-452-1

Chapter 15 - Priciples of Chemical Equilibrium - Exercises - Writing Equilibrium Contants Expressions - Page 688: 1


(a) $$2COF_2(g) \leftrightharpoons CO_2(g) + CF_4(g)$$ $$K_c = \frac{[CO_2][CF_4]}{[COF_2]^2}$$ (b) $$Cu(s) + 2Ag^{+}(aq) \leftrightharpoons Cu^{2+}(aq) + 2Ag(s)$$ $$K_c = \frac{[Cu^{2+}]}{[Ag^{+}]^2}$$ (c) $$S_2O{_8}^{2-}(aq) + 2Fe^{2+}(aq) \leftrightharpoons 2SO{_4}^{2-}(aq) + 2Fe^{3+}(aq)$$ $$K_c = \frac{[SO{_4}^{2-}]^2[Fe^{3+}]^2}{[S_2O{_8}^{2-}][Fe^{2+}]^2}$$

Work Step by Step

1. Write and balance each reaction. (a) $$COF_2(g) \leftrightharpoons CO_2(g) + CF_4(g)$$ $$2COF_2(g) \leftrightharpoons CO_2(g) + CF_4(g)$$ (b) $$Cu(s) + Ag^{+}(aq) \leftrightharpoons Cu^{2+}(aq) + Ag(s)$$ $$Cu(s) + 2Ag^{+}(aq) \leftrightharpoons Cu^{2+}(aq) + 2Ag(s)$$ (c) $$S_2O{_8}^{2-}(aq) + Fe^{2+}(aq) \leftrightharpoons SO{_4}^{2-}(aq) + Fe^{3+}(aq)$$ $$S_2O{_8}^{2-}(aq) + 2Fe^{2+}(aq) \leftrightharpoons 2SO{_4}^{2-}(aq) + 2Fe^{3+}(aq)$$ 2. The $K_c$ expression follows this pattern: $aA + bB \leftrightharpoons cC + dD$ $$K_c =\frac{[Products]}{[Reactants]} = \frac{[C]^c[D]^d}{[A]^a[B]^b}$$ Where solids and pure liquids do not appear on the expression. (a) $$K_c = \frac{[CO_2][CF_4]}{[COF_2]^2}$$ (b) $$K_c = \frac{[Cu^{2+}]}{[Ag^{+}]^2}$$ (c) $$K_c = \frac{[SO{_4}^{2-}]^2[Fe^{3+}]^2}{[S_2O{_8}^{2-}][Fe^{2+}]^2}$$
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