Câu 29:

$a)$

Chất oxh: $\rm KMnO_4$

Chất khử: $\rm SO_2$

$\rm ×5\ \hspace{0,1cm}|\ \mathop{S}\limits^{+4}\to\mathop{S}\limits^{+6}+2e\\ ×2\ |\ \mathop{Mn}\limits^{+7}+5e\to \mathop{Mn}\limits^{+2}$

Cân bằng:

$\rm 5SO_2+2KMnO_4+2H_2O\xrightarrow\ 2MnSO_4+K_2SO_4+2H_2SO_4 $

$b)\\ n_{SO_2}=\dfrac{\frac{123,95}{1000}}{24,79}=5.10^{-3}(mol)\\ n_{KMnO_4}=\dfrac{2}{5}n_{SO_2}=2.10^{-3}(mol)\\ V_{dd\ KMnO_4}=\dfrac{2.10^{-3}}{0,02}=0,1(l)$

Câu 30:

$CH\equiv CH_{(g)}+2H_{2(g)}\xrightarrow\ CH_3-CH_{3(g)}\\ \Delta rH^{0}_{298}=\bigg[2E_{b(C-H)}+E_{b(C\equiv C)}+2E_{b(H-H)}\bigg]-\bigg[6E_{b(C-H)}+E_{b(C-C)}\bigg]\\=\bigg[2.414+839+2.436\bigg]-\bigg[6.414+347\bigg]\\=-292(kJ)$