The mass fraction of hydrogen in a compound of group 14 element is 0.25. The chemical formula of the hydride of this element is(at. wt.,C=12,Si=28,H=1 )

Let element of group 14 is A and its mass number is B. Since valency of group 14 element is 4, so its formula is AH4 Mass fraction of hydrogen in                      AH4=4×1B+4Hence,        4B+4=0.25 (given); 4=0.25B+4×0.25Or        0.25B=4−1=3.So,               B=30.25=12 (= at. wt. of C)∴ Chemical formula of AH4 = CH4.