Question

Determine the number of atoms present in 4.0g of sodium hydroxide [ Na=23, C=12, O=16, H=1 , 1

mole of a substance contains 6.022 ×1023 atoms ]

Answer 1

Molar mass NaOH = 40g/mol

Mol NaOH in 4.0g = 0.1 mol

1 mol NaOH has 6.022×10^23 molecules

0.1 mol = 6.022*10^22 molecules

3atoms / molecule $= 3 × 6.022×10^{22} = 1.8×10^{23} atoms$