1
COMEDK 2024 Evening Shift
MCQ (Single Correct Answer)
+1
-0

A dry cell consists of a moist paste of $$\mathrm{NH}_4 \mathrm{Cl}$$ and $$\mathrm{ZnCl}_2$$ contained in a $$\mathrm{Zn}$$ casing which encloses a Carbon rod surrounded by black $$\mathrm{MnO}_2$$ paste. What is the role of $$\mathrm{ZnCl}_2$$ in it?

A
It prevents pressure being developed in the cell due to $$\mathrm{NH}_3$$ gas formation.
B
It serves as cathode thus permitting Carbon rod to act as anode.
C
It acts as the anode while Carbon rod acts as the cathode.
D
It keeps the contents dry and prevents leakage of electrolyte.
2
COMEDK 2024 Evening Shift
MCQ (Single Correct Answer)
+1
-0

A current of 3.0A is passed through 750 ml of 0.45 M solution of CuSO$$_4$$ for 2 hours with a current efficiency of 90%. If the volume of the solution is assumed to remain constant, what would be the final molarity of CuSO$$_4$$ solution?

A
0.296
B
0.4
C
0.237
D
0.316
3
COMEDK 2024 Evening Shift
MCQ (Single Correct Answer)
+1
-0

Arrange the following redox couples in the increasing order of their reducing strength:

$$\begin{array}{ll} {[\mathrm{A}]=\mathrm{Cu} / \mathrm{Cu}^{2+}} & \mathrm{E}^0=-0.34 \mathrm{~V} \\ {[\mathrm{~B}]=\mathrm{Ag} / \mathrm{Ag}^{+}} & \mathrm{E}^0=-0.8 \mathrm{~V} \\ {[\mathrm{C}]=\mathrm{Ca} / \mathrm{Ca}^{2+}} & \mathrm{E}^0=+2.87 \mathrm{~V} \\ {[\mathrm{D}]=\mathrm{Cr} / \mathrm{Cr}^{3+}} & \mathrm{E}^0=+0.74 \mathrm{~V} \end{array}$$

A
B < A < D < C
B
A < C < B < D
C
C < D < A < B
D
D < A < C < B
4
COMEDK 2023 Morning Shift
MCQ (Single Correct Answer)
+1
-0

Assuming no change in volume, the time required to obtain solution of $$\mathrm{pH}=4$$ by electrolysis of $$100 \mathrm{~mL}$$ of $$0.1 \mathrm{~M} \mathrm{~NaOH}$$ (using current $$0.5 \mathrm{~A}$$ ) will be

A
1.93 s
B
2.63 s
C
1.80 s
D
4.26 s
COMEDK Subjects
EXAM MAP
Medical
NEET
Graduate Aptitude Test in Engineering
GATE CSEGATE ECEGATE EEGATE MEGATE CEGATE PIGATE IN
Civil Services
UPSC Civil Service
Defence
NDA
CBSE
Class 12