Answer:
1)NaCl=23+35,5=58,5 grams/molecules
2)H2O=2+16=18 grams/molecules
3)O2=2*16=32 grams/molecules
4)Fe2O3=2*56+3*16=160 grams/molecules
5)Na2O=2*23+16=62 grams/molecules
6)Cl2=2*35,5=71 grams/molecules
Explication
When you need to calculate the molar mass .
1 use the periodic table
2 look at the atomic mass for each element
3 if you have a number after the element multiply it by that number just that element
4 and then calculate the amount of the whole substance and that will be your molar mass