Question

Density of water is 1g/mL. The concentration of water in mol/litre is:

• A. 1000
• B. 18
• C. 0.018
• D. 55.5

Answer 1

The correct option is (C)

Density is defined as the ratio of the mass of a substance to the volume of the same substance.

$Density=\frac{mass}{volume}$

Step 1: Calculating the mass of substance

$mass=density\times volume$

Given, $d=1g/mL$

$V=1L=1000mL$

$mass=1g/mL\times 1000mL$

Therefore, $mass=1000g$

Step 2: Calculating the molarity of solution

The molarity of solution is defined as the number of moles of solute dissolve in one litre of solution.

$Molarity=\frac{numberofmolesofsolute}{volumeofsolution\left(L\right)}$

$M=\frac{Givenmass}{molarmass\times volume\left(L\right)}$

$M=\frac{1000g}{18g/mol\times 1L}$

$M=55.55moles/L$