Question

A solution contains 1.32×10-2 M lead nitrate and 1.16×10-2 M copper(II) acetate. Solid sodium carbonate is added slowly to this mixture.
A. What is the formula of the substance that precipitates first? formula =
B. What is the concentration of carbonate ion when this precipitation first begins? [CO32-] = M

Answer 1

Answer:

CuCO₃ is the formula of the substance that will precipitate out first

the concentration of carbonate ion when this precipitation first begins = 1.212 × 10⁻¹¹ M

Explanation:

$Pb(NO_3)_2 \ + \ Na_2CO_3 -----> PbCO_3 \ + \ 2NaNO\\\\ksp \ of \ PbCO_3 = 1.6*10^{-13} \\\\ \\Cu (CH_3COO)_2 \ + \ Na_2CO_3 ------> CuCO_3 \ + \ Na(C_2H_3O_2)\\\\ksp \ of CuCO_3 = 1.3*10^{-10}\\\\As \ ksp \ of CuCO_3 > PbCO_3\\\\Then \ \ CuCO_3 \ will \ precipitate \ out \ first$

$PbCO_3 ----> Pb^{2+}_{(aq)} + CO^{2-}_{3(aq)}$

$[Pb^{2+}]$ will be $[Pb(NO_3)_2] = 1.32 *10^{-2} \ M$

$ksp = [Pb^{2+}][CO^{2-}_3]$

$1.6*10^{-13} = (1.32*10^{-2})(CO^{2-}_3)\\\\(CO^{2-}_3) = \frac{1.6*10^{-13}}{(1.32*10^{-2})}\\\\(CO^{2-}_3) = 1.212 *10^{-11} \ \ M$