Calculate the number of Cl- and …

The chemical formula and molar mass of calcium chloride are respectively CaCl2 and 111 g respectively. Thus, there are 6.022{tex}\times{/tex}1023 formula units in 111g of CaCl2. So,
number of formula units of CaCl2 in 111 g of CaCl2 = 6.022 {tex}\times{/tex}1023
number of formula units of CaCl2 in 1g of CaCl2 = {tex}\frac{(6.022\times1023)}{111}{/tex}

number of formula units in 222g of CaCl2 ={tex}\frac{(6.022\times1023\times222)}{111}{/tex} 
= 12.044 {tex}\times{/tex} 1023
Now, each formula unit of CaCl2 contains one Ca2+ ion and two Cl- ions. Therefore
number of Ca2+ ions in one unit of CaCl2 = 1
number of Ca2+ ions in 12.044 {tex}\times{/tex} 1023 units of CaCl2 = 1 {tex}\times{/tex} 12.044 {tex}\times{/tex} 1022 = 1.2044 {tex}\times{/tex} 1024
Similarly
number of Cl- ions in one unit of CaCl2 = 2
number of Cl- ions in 12.044 {tex}\times{/tex} 1023 units of CaCl2 = 2 {tex}\times{/tex} 12.044 {tex}\times{/tex} 1023
= 2.4088 {tex}\times{/tex} 1024
Hence, there are 1.2044 {tex}\times{/tex} 1024 Ca2+ ions and 2.4088 {tex}\times{/tex} 1024 Cl- ions in 222 g of CaCl2.