1) Masa moleculara Na2SO4=2·23+32+4·16=142g/mol
un mol Na2SO4.......142g
0,2moli Na2SO4.....x g
x=(0,2·142)/1=28,4g
2) Masa moleculara
HNO3=1+14+3·16=63g/mol
un mol.....63g
5moli.....y g
y=5·63=315g
3)Masa moleculara
Ca(OH)2=40+2·16+2·1=40+32+2=74g/mol
un mol......74g
10moli......z g
z=10·74=740g