1
WB JEE 2026
MCQ (Single Correct Answer)
+2
-0.5
Change Language

A $5.0 \mathrm{~cm}^3$ solution of $\mathrm{H}_2 \mathrm{O}_2$ liberates 1.27 g of iodine from an acidified KI solution. The percentage strength of $\mathrm{H}_2 \mathrm{O}_2$ is close to

A

$11 \cdot 2$

B

$5\cdot8$

C

$1\cdot9$

D

$3 \cdot 4$

2
WB JEE 2026
MCQ (Single Correct Answer)
+2
-0.5
Change Language

An organic compound undergoes first order decomposition.The time taken for its decomposition to $\frac{1}{8}$ th and $\frac{1}{10}$ th of its initial concentration are $t_{1 / 8}$ and $t_{1 / 10}$ respectively.The value of $\left[\frac{t_{1 / 8}}{t_{1 / 10}}\right]$ is [Given $\log _{10} 2=0 \cdot 3$ ]

A

0.9

B

0.6

C

0.3

D

0.5

3
WB JEE 2026
MCQ (Single Correct Answer)
+2
-0.5
Change Language

For the metal complex $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{SO}_4\right] \mathrm{Br}$ ,coordination number,oxidation number,number of $d$-electrons and number of unpaired $d$-electrons are respectively

A

$6,3,6,0$

B

$6,2,6,0$

C

$7,2,6,2$

D

$6,2,7,0$

4
WB JEE 2026
MCQ (Single Correct Answer)
+2
-0.5
Change Language

$$ \mathrm{RO}-\mathrm{CH}_2-\mathrm{C} \equiv \mathrm{CH} \xrightarrow{\mathrm{X}} \xrightarrow{\mathrm{Y}} \mathrm{RO}^{-} \mathrm{CH}_2-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}_2 \mathrm{CH}_2-\mathrm{Br} $$

To carry out the above conversion X and Y are respectively

A

$\mathrm{NaNH}_2, \mathrm{Br}-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{Cl}$

B

$\mathrm{NaNH}_2, \mathrm{I}-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{Br}$

C

$\mathrm{NaNH}_2, \mathrm{~F}-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{Br}$

D

$\mathrm{NaNH}_2, \mathrm{CH}_2=\mathrm{CH}-\mathrm{Br}$