JEE Mains · Chemistry · STD 12 -1. Solution and colligative properties

The molarity of a \(70 \%\) (mass \(/\) mass) aqueous solution of a monobasic acid \((\mathrm{X})\) is __________ \(\times 10^{-1}\) M.(Nearest integer)
[Given: Density of aqueous solution of (X) is \(1.25 \mathrm{~g} \mathrm{~mL}^{-1}\)
Molar mass of the acid is \(70 \mathrm{~g} \mathrm{~mol}^{-1}\) ]

A 120
B 122
C 124
D 125

Verified Solution

Answer & Solution

Correct Answer

(D) 125

Step-by-step Solution

Detailed explanation

Moles of solute \(=\frac{70}{70}=1\) Volume of solution \(=\frac{100}{1.25}=80 \mathrm{~mL}\) \(\begin{aligned} & M=\frac{1}{80} \times 1000=12.5 \\ & M=125 \times 10^{-1} \end{aligned}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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Match List\(-I\) with List\(-II\).

List\(-I\)	List\(-II\)
\(A\) \(16\,g \text { of } CH _{4( g )}\)	\(I\) Weighs \(28\,g\)
\(B\) \(1\,g \text { of } H _{2( g )}\)	\(II\) \(60.2 \times 10^{23}\) electrons
\(C\) \(1\,mole \text { of } N _{2( g )}\)	\(III\) Weighs \(32\,g\)
\(D\) \(0.5\,mol\) of \(SO _{2( g )}\)	\(IV\) Occupies \(11.4\,L\) volume at STP

Choose the correct answer from the options given below:

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