Question

Calculate the number of molecules in 1 kg of calcium chloride.

Answer 1

1 mole of calcium chloride ${\mathrm{CaCl}}_2$ = Avogadro's number of molecules of ${\mathrm{CaCl}}_2$ = 6.023×10²³ molecules of ${\mathrm{CaCl}}_2$

Also, 1 mole of ${\mathrm{CaCl}}_2$ = Molecular mass of ${\mathrm{CaCl}}_2$

i.e., Molecular mass of ${\mathrm{CaCl}}_2$ = 6.023×10²³ molecules of ${\mathrm{CaCl}}_2$

Molecular mass of calcium chloride = Mass of calcium +2 x Mass of chlorine

= 40 + 2 x 35.5

= 110 g

110 g of ${\mathrm{CaCl}}_2$ = $6.022\times {10}^{23}$molecules of ${\mathrm{CaCl}}_2$

1 kg of ${\mathrm{CaCl}}_2$ = $\frac{6.022\times {10}^{23}}{110}\times 1000$

1 kg of ${\mathrm{CaCl}}_2$contains $5.42\times {10}^{24}$molecules of ${\mathrm{CaCl}}_2$ .