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)

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 $=\frac{30}{291 \times 4.3}$
$=0.023\,M$