Question

The decomposition reaction, 4HNO₃ (g) $\rightleftarrows$

4NO₂ (g) + 2H₂O (g) + O₂ (g)

is started with pure HNO₃ (g). If p is the total pressure at equilibrium, then

• A. K_p = ($p_{O_{2}}$)⁷/ (p – 7$p_{O_{2}}$)⁴
• B. K_p = 1024($p_{O_{2}}$)⁷/ (p – 7$p_{O_{2}}$)⁴
• C. K_p = 7$p_{O_{2}}$ / (p – 4$p_{O_{2}}$)
• D. K_p = ( p –$p_{O_{2}}$)⁷/ (p – 7$p_{O_{2}}$)⁴

Answer 1

Answer: (B)

K_p = 1024($p_{O_{2}}$)⁷/ (p – 7$p_{O_{2}}$)⁴

Answer 2

4HNO₃ (g) $\rightleftarrows$ 4NO₂ (g) + 2H₂O (g) + O₂ (g)

p_o — —

p_o – 4$p_{O_{2}}$ 4$p_{O_{2}}$ 2$p_{O_{2}}$ $p_{O_{2}}$

\ p_o + 3$p_{O_{2}}$= p

\ p_o = (p – 3$p_{O_{2}}$)

\ p_o – 4$p_{O_{2}}$ = p – 3$p_{O_{2}}$ – 4$p_{O_{2}}$ = p – 7$p_{O_{2}}$

\K_p = $\frac{(4p_{O_{2}})^{4}(2p_{O_{2}})^{2} \times p_{O_{2}}}{(p - 7p_{O_{2}})^{4}}$ = $\frac{1024 \times {p_{O}}_{2}^{7}}{(p - 7p_{O_{2}})^{4}}$