Calculate the molarity of each of the following solutions: (a) 30 g of Co(NO3)2. 6H2O in 4.3 L of solution (b) 30 mL of 0.5 M H2SO4 diluted to500 mL.

Molarity is the concentration of a solution expressed as the number of moles of solute per litre of solution.


Molarity =


(a) Given,


In 4.3 L of solution there is 30 g of Co(NO3)2. 6H2O


Molar mass of Co(NO3)2.6H2O = (1 × 59 + 2 × (1 × 14 + 3 × 16) + 6 × 18)


= 291 g/mol.


∴ Moles = = 0.103 mol.


Now, Molarity =


= 0.023 M


(b) Given,


30 mL of 0.5 M H2SO4 diluted to500 mL.


In 1000 mL of 0.5 M H2SO4, number of moles present is 0.5 mol.


∴ In 30 mL of 0.5 M H2SO4, number of moles present = mol.


= 0.015 mol.


∴ Molarity =


= 0.03 M.


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