Question

What is the concentration of Ag⁺ ion in a 1L solution containing 0.02 mol of AgNO₃ and 0.14 mol of NH₃. For Ag(NH₃)₂⁺, K_instab = 10⁸

• A. 2 × 10^–7(M)
• B. 10^–8(M)
• C. 2 × 10^–8(M)
• D. 2 × 10^–9(M)

Answer 1

Answer: (C)

2 × 10^–8(M)

Answer 2

Ag⁺ + 2NH₃Ag(NH₃)₂⁺ 0.02 mol 0.14 mol

—0.1 mol 0.02 mol

10⁸ = $\frac { \left[ \mathrm { Ag } \left( \mathrm { NH } _ { 3 } \right) _ { 2 } ^ { + } \right] } { \left[ \mathrm { Ag } ^ { + } \right] \left[ \mathrm { NH } _ { 3 } \right] ^ { 2 } }$ = $\frac { 0.02 } { \left[ \mathrm { Ag } ^ { + } \right] \times 0.01 }$

or [Ag⁺] = 2 × 10^–8 (M)