1. The cell constant of a conductivity cell is defined as:
A.
l/A
B.
A/l
C.
l × A
D.
1/(l × A)
Correct Answer:
l/A
Explanation:
Cell constant is the ratio of the distance between the electrodes (l) to the area of cross-section of the electrodes (A), so it is l/A.
2. What is the SI unit of cell constant?
A.
m
B.
m⁻¹
C.
S m⁻¹
D.
Ω m
Correct Answer:
m⁻¹
Explanation:
Cell constant is l/A, with l in metres and A in square metres. Therefore, its unit is m/m², or m⁻¹.
3. A conductivity cell has an electrode separation of 2 cm and an electrode area of 1 cm². Its cell constant is:
A.
0.5 cm⁻¹
B.
1 cm⁻¹
C.
2 cm⁻¹
D.
3 cm⁻¹
Correct Answer:
2 cm⁻¹
Explanation:
Cell constant = l/A = 2 cm/1 cm² = 2 cm⁻¹.
4. If the distance between the electrodes is increased while their area remains unchanged, the cell constant will:
A.
Decrease
B.
Increase
C.
Become zero
D.
Remain unchanged
Correct Answer:
Increase
Explanation:
Since cell constant is l/A, increasing l while keeping A constant increases the cell constant.
5. If the area of the electrodes is doubled while the distance between them remains unchanged, the cell constant will:
A.
Double
B.
Become four times larger
C.
Become half
D.
Remain unchanged
Correct Answer:
Become half
Explanation:
Cell constant is inversely proportional to electrode area, as K = l/A. Doubling A makes the cell constant half its original value.
6. The conductance G of a solution and its conductivity κ are related to the cell constant K by:
A.
κ = G/K
B.
κ = G × K
C.
κ = K/G
D.
κ = G + K
Correct Answer:
κ = G × K
Explanation:
Conductivity is calculated using κ = G × K, where K is the cell constant.
7. A conductivity cell has a cell constant of 1.5 cm⁻¹. If the conductance of a solution is 0.02 S, its conductivity is:
A.
0.0133 S cm⁻¹
B.
0.03 S cm⁻¹
C.
1.48 S cm⁻¹
D.
0.75 S cm⁻¹
Correct Answer:
0.03 S cm⁻¹
Explanation:
Using κ = G × K, conductivity = 0.02 S × 1.5 cm⁻¹ = 0.03 S cm⁻¹.
8. The cell constant of a conductivity cell is generally determined using a solution of:
A.
Unknown concentration
B.
Known conductivity
C.
Distilled water only
D.
Pure solvent with zero conductivity
Correct Answer:
Known conductivity
Explanation:
A standard solution with known conductivity is used to determine the cell constant from its measured conductance.
9. A conductivity cell has an electrode distance of 1 cm and electrode area of 0.5 cm². The cell constant is:
A.
0.5 cm⁻¹
B.
1 cm⁻¹
C.
2 cm⁻¹
D.
5 cm⁻¹
Correct Answer:
2 cm⁻¹
Explanation:
Cell constant = l/A = 1 cm/0.5 cm² = 2 cm⁻¹.
10. Which change would decrease the cell constant of a conductivity cell?
A.
Increasing the distance between electrodes
B.
Decreasing the electrode area
C.
Increasing the electrode area
D.
Increasing both distance and area equally
Correct Answer:
Increasing the electrode area
Explanation:
Because K = l/A, increasing the electrode area while keeping the distance fixed decreases the cell constant.
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