Question

$100{\text{cm}}^3$ of a 0.1 M $HCl$ solution is mixed with $100{\text{cm}}^3$ of a 0.2 N $NaOH$ solution. The concentration of excess reagent left and the nature of resulting solution is:

• A. Molarity = 0.1 M and the solution is basic
• B. Molarity = 0.1 M and the solution is acidic
• C. Molarity = 0.05 M and the solution is basic
• D. Molarity = 0.05 M and the solution is acidic

Answer 1

The correct option is C Molarity = 0.05 M and the solution is basic

$\text{Molarity}=\frac{\text{number of moles of solute}}{\text{volume of solution in mL}}\times 1000$

$\text{Number of moles of}HCl=\frac{100\times 0.1}{1000}=0.01$

$\text{Number of moles of}NaOH=\frac{100\times 0.2}{1000}=0.02$

Since the moles of base are greater, the solution will be basic.
Moles of NaOH left after neutralization
$=0.02–0.01=0.01$
Molarity of NaOH in the resultant solution
$=\frac{0.01}{200}\times 1000=0.05M$