Question

Assertion :One molar aqueous solution is more concentrated than that of $1$ molal aqueous solution. Reason: Molarity is a function of temperature as volume depends on temperature

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

$M=\frac{Molesofsolute}{Volumeofsolution\left(litres\right)}$

$Molality=\frac{Molesofsolute}{Massofsolvent\left(kg\right)}$

$1$ $molar$ aqueous solution is more concentrated than $1$ $molal$ aqueous solution because $1$ $molar$ solution contain $1$ $mole$ solute in $1$ $litre$ solution which include both solute and solvent. So, the mass of the solvent is less than $1000$ $g$. Therefore, $1$ $molar$ aqueous solution contain $1$ $mole$ of $solute$ in less than $1000$ $g$ of solvent while. $1$ $molal$ solution has $1$ $mole$ of solute in $1000$ $gram$ of solvent. Hence, concentration will be more in $1$ $molar$ solution.

Also, molarity is a function of temperature as volume depends upon temperature

Ex. Osmotic pressure equation $\pi =iCRT$

$C\propto \frac{1}{T}$ where $C$ is concentration.