Question

What is the concentration of the solution obtained when 40 g of NaOH is dissolved in 1 L of water?

• A. 0.5 M
• B. 1 M
• C. 2 M
• D. 5 M

Answer 1

The correct option is B

1 M

Mass of NaOH taken = 40 g
The volume of the aqueous solution= 1 L
Molarity of a solution is given by the formula = $\frac{\text{Number of moles of solute}}{\text{Volume of the solution (litres)}}$ ....(i)

Number of moles of solute= $\frac{\text{Given mass}}{\text{Gram molecular mass}}$ ....(ii)
Gram molecular mass of NaOH = 40 g
After inserting the values of given mass of NaOH and its gram molecular mass in equation (ii), we get
Number of moles of solute = $\frac{40}{40}$ = 1
After inserting the values of the number of moles of NaOH and its volume of the solution in equation (i) we get
Molarity of a solution = $\frac{1}{1}$ = 1 M
Hence, the molarity of the solution is 1 M.