Vamos a isso)
a) MM(H2S)=2+32=34g/mol
se 34g--------------1mol
300g---------------X
X=8,82moles de H2S
b) MM(H2SO4)= 2+32+64=98g/mol
1mol------------------98g
x----------------------500g
x=5,1moles de H2SO4
c) MM(HI)=1+127=128g/mol
n=m/MM
n=128/128
n=1mol