Đáp án:

$\rm n_{alcohol}=2n_{H_2}=0,12\ (mol)$

$\rm n_{O_2}=\dfrac{28,224}{22,4}=1,26\ (mol)$

Dồn chất cho alcohol: $\begin{cases}\rm CH_2:a\ (mol)\\\rm H_2O:0,12\ (mol)\end{cases}$

Tương quan đốt:

$\rm n_{CH_2}=\dfrac{n_{O_2}}{1,5}=0,84\ (mol)$

Bảo toàn nguyên tố C:

$\rm n_{CO_2}=n_{CaCO_3}=n_{CH_2}=0,84\ (mol)$

$\rm n_{H_2O}=n_{CO_2}+n_{alcohol}=0,96\ (mol)$

Khối lượng dd giảm:

$\rm\Delta m=m_{CO_2}+m_{H_2O}-m_{CaCO_3}\\\kern,8cm=0,84×44+0,96×18-0,84×100\\\kern,8cm=-29,76\ (g)$