Calcium chloride when dissolved in water dissociates into its ions according to the following equation.

CaCl(aq) Ca2+ (aq) + 2Cl (aq)


Calculate the number of ions obtained from CaCl2 when 222 g of it is dissolved in water.

Molar mass of CaCl2 = The atomic mass of Ca + 2 × the atomic mass of Cl

= 40 + 35.5 × 2 = 111 g/mol


1 mole of calcium chloride = 111g


Thus, 222g of CaCl2 is equivalent to 2 moles of CaCl2


Since 1 formula unit CaCl2 gives 3 ions (one Ca2+ cation and two Cl- anions),


Therefore, 1 mole of CaCl2 will give 3 moles of ions


2 moles of CaCl2 would give 3 × 2 = 6 moles of ions.


No. of ions = No. of moles of ions × Avogadro number


= 6 × 6.022 ×1023


= 36.132 ×1023


= 3.6132 ×1024 ions


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