Question

Calculate the molarity of a solution of $30\,g$ of $Co(NO_3)_2.6H_2O$ in $4.3\, L$ of solution ? Consider atomic mass of $Co = 59\, u$ , $N = 14\, u$ , $O = 16\,u$ , $H = 1\,u$

• A. $0.023 \,M$
• B. $0.23 \,M$
• C. $0.046 \,M$
• D. $0.46 \,M$

Answer 1

Answer: (A)

$0.023 \,M$

Answer 2

Mass =$30\, g$
Molar mass $=59+14\times 2+12\times 16+12\times1=291$
Moles of $Co(NO_{3})_{2}\cdot 6H_{2}O=\frac{30}{291}$
Molarity $=\frac{30}{291 \times 4.3}$
$=0.023\,M$