Question

2.5 liter of 1 M NaOH solution is mixed with another 3 liters of 0.5 M NaOH solution. Then the molarity of the resulting solution is:

• A. 0.80 M
• B. 1.0 M
• C. 0.73 M
• D. 0.50 M

Answer 1

Answer: (C)

0.73 M

$\begin{array}{c}\text{No. of moles in}2.5L,\text{1 M}NaOH=2.5\times 1\\ =2.5\text{moles}\\ \\ \text{No. of moles in}3L,0.5\text{M}NaOH=3\times 0.5\\ =1.5\text{moles}\\ \\ \text{Total moles}=1.5+2.5=4\text{moles}\end{array}$

$\begin{array}{c}\text{Total volume}=2.5+3=5.5L\\ \\ \text{Molarity}=\frac{4}{5.5}=0.728\approx 0.73\\ \\ \text{Hence option}C\text{is correct}\end{array}$