Question

Calculate the resultant molarity on mixing 2500 mL of a 2.5 M $HN{O}_3$ solution and 157.5 g of $HN{O}_3$.

• A. 3.5 M
• B. 4.7 M
• C. 2.8 M
• D. 1.5 M

Answer 1

The correct option is A 3.5 M

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

$\text{Initial number of moles of solute}=\frac{2.5\times 2500}{1000}=6.25mol$

$\text{Moles of}HN{O}_3\text{added}=\frac{157.5}{63}=2.5$

$\text{Total moles}=6.25+2.5=8.75\text{mol}$

$\text{New molarity}=\frac{8.75}{2500}\times 1000=3.5M$

Molarity after addition of solute will be $3.5M$.