1
COMEDK 2026 Morning Shift
MCQ (Single Correct Answer)
+1
-0

Identify the correct mathematical expression which represents the variation in molar conductivity of a weak acid having concentration C and ionisation constant $\mathrm{K}_{\mathrm{a}}$

( $\lambda_m^{\infty}=$ molar conductivity at infinite dilution, $\lambda_{\mathrm{m}}=$ molar conductivity at concentration C )

A

$K_a=\lambda_m^2 C / \lambda_m^{\infty}\left(\lambda_m^{\infty}-\lambda_m\right)$

B

$K_a=\lambda_m \lambda_m^{\infty}-\left(\lambda_m^{\infty}\right)^2+\lambda_m^2 C$

C

$\lambda_m+\lambda_m^{\infty}+K_a C^{\frac{1}{2}}=0$

D

$K_a=\lambda_m^2 C / \lambda_m^{\infty}\left(\lambda_m^{\infty}+\lambda_m\right)$

2
COMEDK 2026 Morning Shift
MCQ (Single Correct Answer)
+1
-0

Lassaigne's test for the detection of nitrogen fails in

A

$\mathrm{NH}_2-\mathrm{NH}_2 \mathrm{HCl}$

B

$\mathrm{NH}_2 \mathrm{CONHNH}_2 \mathrm{HCl}$

C

$\mathrm{C}_6 \mathrm{H}_5 \mathrm{NHNH}_2 \mathrm{HCl}$

D

$\mathrm{NH}_2 \mathrm{CONH}_2$

3
COMEDK 2026 Morning Shift
MCQ (Single Correct Answer)
+1
-0

$\Delta \mathrm{H}$ and $\Delta \mathrm{S}$ for a reaction are $35.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and $83.6 \mathrm{~J} \mathrm{~K}^{-1}$ respectively. Assuming that $\Delta \mathrm{H}$ and $\Delta \mathrm{S}$ do not vary with temperature, the reaction is spontaneous when:

A

$\mathrm{T}<425 \mathrm{~K}$

B

$\mathrm{T}<350 \mathrm{~K}$

C

$\mathrm{T}>425 \mathrm{~K}$

D

$T>298 \mathrm{~K}$

4
COMEDK 2026 Morning Shift
MCQ (Single Correct Answer)
+1
-0

When the initial concentration of a zero order reaction is doubled, the half-life of the reaction is:

A

doubled

B

not changed

C

tripled

D

halved