# What is the mass of Cl in 21 g of NaCl?

Nov 7, 2015

12.78g

#### Explanation:

21g of $N a C l$ is equivalent to 0.36mol.

$N a$ (atomic mass = 23 g/mol), $C l$ (atomic mass = 35.5g/mol)

Mole = $\left(\text{Atomic Mass") ("Molar Mass}\right)$

Total molar mass of $N a C l$ = 23 + 35.5 = 58.5 g/mol

Mole = $21 \cancel{g} N a C l$ x $\frac{\text{1 mol}}{58.5 \cancel{g}} N a C l$ = 0.36 mol NaCl

1 mol of NaCl consists of 1 mol of Na ion and 1 mol of Cl ion

or

$N a C l$ $\rightarrow$ $N {a}^{+}$ + $C {l}^{-}$

Therefore, 0.36mol of NaCl is equal to 0.36mol of Cl.

Mass of Cl = (Mole $C l$) (Atomic Mass $C l$)

Mass of Cl = $0.36 \text{mol Cl}$ x "35 g"/ (1 cancel "mol") Cl

Mass of Cl = 12.78g $C l$