a)  $H_2+C{l}_2\to 2HCl$  

b)  $S{O}_2+H_{2}O\to H_{2}S{O}_3$ $S{O}_2+H_{2}O\to H_{2}S{O}_3$  

c)  $N_2{O}_3+H_{2}O\to 2HN{O}_3$  

d)  $H_2+S\to H_{2}S$  

e)  $N_2{O}_5+H_{2}O\to 2HN{O}_3$  

f)  $P_4{O}_{10}+6H_{2}O\to 4H_{3}P{O}_4$