Question

8. Convert into mole.
(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of carbon dioxide.​

Answer 1

$mole \: = \frac{mass}{molar \: mass} \\ molar \: mass \: of \: oxygen \: gas \: = 16 \times 2 \\ = 32 \\ mole \: = \frac{12}{32} \\ mole \: = 0.375mol$

$molar \: mass \: of \: h2o \: = (1 \times 2) + (1 \times 16) \\ = 2 + 16 \\ = 18 \\ mole \: = \frac{mass}{molar \: mass } \\ = \frac{20}{18} \\ = 1.11mol$

$molar \: mass \: of \: co2 = (1 \times 12) + (2 \times 16) \\ = 12 + 32 \\ = 44 \\ mole \: = \frac{mass}{molar \: mass} \\ = \frac{22}{44} \\ = 0.5mol$

SI unit of molar mass is g/mol

Hope this helps you