a, $CH_3COOH+NaOH\to CH_3COONa+H_2O$
$n_{NaOH}=\frac{10}{40}=0,25 mol$
$\Rightarrow n_{CH_3COOH}=n_{CH_3COONa}=0,25 mol$
$m_{CH_3COONa}=0,25.82=20,5g$
b,
$C_{M_{CH_3COOH}}=\frac{0,25}{0,5}=0,5M$
c,
$n_{CH_3COOH}=0,25:2=0,125 mol$
$2CH_3COOH+K_2CO_3\to 2CH_3COOK+CO_2+H_2O$
$\Rightarrow n_{K_2CO_3}= 0,0625mol$
$m_{dd K_2CO_3}=\frac{0,0625.138.100}{20}=43,125g$