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

A first order reaction is $50 \%$ complete in 30 minutes at 300 K and in 10 minutes at 320 K . The activation energy of the reaction ( $E_a$ ) is: $\left[R=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1} ; \log 2=0.3010 ; \log 3=0.4771\right]$

A

$75.2 \mathrm{~kJ} \mathrm{~mol}^{-1}$

B

$43.8 \mathrm{~kJ} \mathrm{~mol}^{-1}$

C

$23.7 \mathrm{~kJ} \mathrm{~mol}^{-1}$

D

$52.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$

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

Which of the following factors is altered by the addition of a catalyst during a chemical reaction?

A

Internal energy

B

Activation energy

C

Enthalpy

D

Entropy

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

The standard enthalpies of formation of $\mathrm{CH}_4(\mathrm{~g}), \mathrm{CO}_2(\mathrm{~g})$ and $\mathrm{H}_2 \mathrm{O}(\mathrm{l})$ are $-74.8 \mathrm{~kJ} \mathrm{~mol}^{-1},-393.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and $-285.8 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively. Then the enthalpy change for the given reaction in $\mathrm{kJ} \mathrm{mol}^{-1}$ will be:

$$ 2 \mathrm{CH}_4(\mathrm{~g})+4 \mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{CO}_2(\mathrm{~g})+4 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) $$

A

$ -890.3$

B

$+890.3$

C

$+1780.6$

D

$ -1780.6$

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

With reference to the two statements Assertion and Reason, choose the correct option.

Assertion: The order of reactivity towards $\mathrm{S}_{\mathrm{N}} 1$ reaction is: $\mathrm{C}_6 \mathrm{H}_5-\mathrm{CH}_2 \mathrm{Br}>\left(\mathrm{CH}_3\right)_3-\mathrm{C}-\mathrm{Br}>\left(\mathrm{CH}_3\right)_2-\mathrm{CH}-\mathrm{Br}$.

Reason: Among the given 3 compounds, the Benzyl carbocation formed is the most stable while Isopropyl carbocation is the least stable one.

A

Reason is correct but Assertion is wrong

B

Both Assertion and Reason are correct and Reason is the correct explanation of Assertion

C

Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion

D

Assertion is correct but Reason is wrong