Giải bài 9 trang 257 - SGK môn Hóa học lớp 11 nâng cao

a)

$m_{CH_3COOH}=V.D=10,5\,gam$

$n_{CH_3COOH}=0,175\,mol$

$C_{M\,dd{CH_3COOH}}=\dfrac{0,175}{1,75}=0,1\,M$

b)

$C{{H}_{3}}-COOH\rightleftharpoons \text{ }C{{H}_{3}}CO{{O}^{-}}+{{H^+}}.$

$pH=2,9\Rightarrow [H^+]=10^{-2,9}=1,26.20^{-3}=\alpha.0,1\Rightarrow \alpha=0,0126$

c)

$K=\dfrac{\text{ }\!\![\!\!\text{ }{{H}^{+}}\text{ }\!\!]\!\!\text{ }\text{. }\!\![\!\!\text{ }C{{H}_{3}}CO{{O}^{-}}\text{ }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ }C{{H}_{3}}COOH\text{ }\!\!]\!\!\text{ }}=\dfrac{{{(0,1.\alpha )}^{2}}}{(0,1-0,1\alpha )}\approx 1,{{6.10}^{-5}}$

Ghi nhớ:

Với dung dịch $CH_3COOH$ ta có hằng số cân bằng là:

$K=\dfrac{\text{ }\!\![\!\!\text{ }{{H}^{+}}\text{ }\!\!]\!\!\text{ }\text{. }\!\![\!\!\text{ }C{{H}_{3}}CO{{O}^{-}}\text{ }\!\!]\!\!\text{ }}{\text{ }\!\![\!\!\text{ }C{{H}_{3}}COOH\text{ }\!\!]\!\!\text{ }}$