JEE Main 2021 — Chemistry Physical Chemistry

2021integereasy

$0.4g$ mixture of $\mathrm{NaOH},{\mathrm{Na}}_{2}{\mathrm{CO}}_{3}$ and some inert impurities was first titrated with $\frac{N}{10}\mathrm{HCl}$ using phenolphthalein as an indicator, $17.5\mathrm{mL}$ of $\mathrm{HCl}$ was required at the end point. After this methyl orange was added and titrated. $1.5\mathrm{mL}$ of same $\mathrm{HCl}$ was required for the next end point. The weight percentage of ${\mathrm{Na}}_{2}{\mathrm{CO}}_{3}$ in the mixture is (Rounded-off to the nearest integer)

Official previous-year question

Held on 25 Feb 2021 · Verified 6 Jul 2026.

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Solution

Upto first end point gm equi. of $(\mathrm{NaOH}+{\mathrm{Na}}_{2}{\mathrm{CO}}_{3})=\mathrm{HCl}$

$x+y\times 1=\frac{1}{10}\times 17.5$

$x+y=1.75....(1)$

Upto second end point

$\mathrm{NaOH}+{\mathrm{Na}}_{2}{\mathrm{CO}}_{3}\equiv \mathrm{HCl}$

$x+y\times 2=\frac{1}{10}\times 19$

$x+2y=1.9....(2)$

$y=0.15$

$%{\mathrm{Na}}_{2}{\mathrm{CO}}_{3}=\frac{0.15\times {10}^{-3}\times 106}{0.4}\times 100$

$=3.975%$

$=4%$

Hence answer is $(4)$

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JEE Main 2021 — Chemistry Physical Chemistry

2021integereasy

Official previous-year question

Held on 25 Feb 2021 · Verified 6 Jul 2026.

Did you get this right?

Solution

Upto first end point gm equi. of $(\mathrm{NaOH}+{\mathrm{Na}}_{2}{\mathrm{CO}}_{3})=\mathrm{HCl}$

$x+y\times 1=\frac{1}{10}\times 17.5$

$x+y=1.75....(1)$

Upto second end point

$\mathrm{NaOH}+{\mathrm{Na}}_{2}{\mathrm{CO}}_{3}\equiv \mathrm{HCl}$

$x+y\times 2=\frac{1}{10}\times 19$

$x+2y=1.9....(2)$

$y=0.15$

$%{\mathrm{Na}}_{2}{\mathrm{CO}}_{3}=\frac{0.15\times {10}^{-3}\times 106}{0.4}\times 100$

$=3.975%$

$=4%$

Hence answer is $(4)$

Your note

JEE Main Physical Chemistry in other years

Keep practicing Physical Chemistry

Work through every JEE Main Physical Chemistry PYQ, year by year.

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JEE Main 2021 — Chemistry Physical Chemistry

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Solution

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JEE Main Physical Chemistry in other years

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JEE Main 2021 — Chemistry Physical Chemistry

Did you get this right?

Solution

Your note

JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry