Question

Molarity equation of a mixture of solutions of same substance is given by

• A. $M_{1}+V_{1}\times M_{2}+V_{2}\times M_{3}+V_{3}+...= M_{1}+M_{2}+M_{3}$
• B. $M_{1}V_{1}+M_{2}V_{2}+M_{3}V_{3}+...=M\left(V_{1}+V_{2}+V_{3}\right)$
• C. $\frac{M_{1}}{V_{1}}+\frac{M_{2}}{V_{2}}+\frac{M_{3}}{V_{3}}+ ... = M\left(\frac{1}{V_{1}}+\frac{1}{V_{2}}+\frac{1}{V_{3}}\right)$
• D. $\frac{M_{1}}{V_{1}}\times\frac{M_{2}}{V_{2}}\times\frac{M_{3}}{V_{3}}+ ... = M\left(\frac{1}{V_{1}}\times\frac{1}{V_{2}}\times\frac{1}{V_{3}}\right)$

Answer 1

Answer: (B)

Molarity, $M =$ number of moles/volume of solution
$M=\frac{n}{V}$
for mixture of solutios
$n _{1}+ n _{2}+ n _{3}+\ldots= M _{1} V _{1}+ M _{2} V _{2}+ M _{3} V _{3}+\ldots$
$\left( n _{1}+ n _{2}+ n _{3}+\ldots\right) \times \frac{\left( V _{1}+ V _{2}+ V _{3}+\ldots\right)}{\left( V _{1}+ V _{2}+ V _{3}+\ldots\right)}= M _{1} V _{1}+ M _{2} V _{2}+ M _{3} V _{3}+\ldots$
total number of moles in the mixture $=n_{ T }$, total volume $=V_{ T }$
final molarity $= M _{ T }= M$
$\frac{ n _{ T }}{ V _{ T }} \times\left( V _{1}+ V _{2}+ V _{3}+\ldots\right)= M _{1} V _{1}+ M _{2} V _{2}+ M _{3} V _{3}+\ldots$
$M _{ T } \times\left( V _{1}+ V _{2}+ V _{3}+\ldots\right)= M _{1} V _{1}+ M _{2} V _{2}+ M _{3} V _{3}+\ldots$
or $M \times\left( V _{1}+ V _{2}+ V _{3}+\ldots\right)= M _{1} V _{1}+ M _{2} V _{2}+ M _{3} V _{3}+\ldots$