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# Calculate the molarity of each of the following solutions: (a) 30 g of (CoNO_3)_2. 6H_2O in 4.3 L of solution

2.3   Calculate the molarity of each of the following solutions:

(a)  $\inline 30\; g$ of  $\inline Co(NO_{3})_{2}.\; 6H_{2}O$  in  $\inline 4.3\: L$  of solution

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For finding molarity we need the moles of solute and volume of solution.

So moles of solute :

$= \frac{Given\ mass}{Molar\ mass} = \frac{30}{291} = 0.103$

$Since\ molar\ mass\ of\ Co(NO_3)_2.6H_2O \right = 59 + 2(14 + 3 � 16) + 6 (16 +1 � 2)$

$= 291\ g\ mol^{-1}$

Now,                                     $Molarity = \frac{No.\ of\ moles\ of\ solute}{Volume\ of\ solution\ (l)}$

$= \frac{0.103}{4.3} = 0.023\ M$

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