Undergraduate
Q. In a first-order reaction, if the concentration of reactant decreases from 0.8 M to 0.2 M in 20 minutes, what is the rate constant? (2022)
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A.
0.0347 min⁻¹
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B.
0.0693 min⁻¹
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C.
0.1 min⁻¹
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D.
0.2 min⁻¹
Solution
Using the first-order rate equation, k = (ln[A₀] - ln[A]) / t. Here, k = (ln(0.8) - ln(0.2)) / 20 = 0.0347 min⁻¹.
Correct Answer: A — 0.0347 min⁻¹
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Q. In a first-order reaction, if the half-life is constant, what can be said about the rate constant? (2023)
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A.
It increases with time
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B.
It decreases with time
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C.
It remains constant
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D.
It is zero
Solution
In a first-order reaction, the half-life is constant, which indicates that the rate constant remains constant.
Correct Answer: C — It remains constant
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Q. In a first-order reaction, if the rate constant k is 0.03 min⁻¹, what is the time required for the concentration to decrease to half? (2020)
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A.
23.1 min
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B.
10.0 min
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C.
20.0 min
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D.
15.0 min
Solution
t₁/₂ = 0.693 / k = 0.693 / 0.03 = 23.1 min.
Correct Answer: A — 23.1 min
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Q. In a fluid, what is the relationship between depth and pressure?
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A.
Pressure increases with depth
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B.
Pressure decreases with depth
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C.
Pressure remains constant
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D.
Pressure is independent of depth
Solution
In a fluid, pressure increases with depth due to the weight of the fluid above.
Correct Answer: A — Pressure increases with depth
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Q. In a food chain, which of the following is a primary consumer? (2019)
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A.
Grass
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B.
Rabbit
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C.
Fox
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D.
Eagle
Solution
A rabbit is a primary consumer as it feeds on plants (producers).
Correct Answer: B — Rabbit
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Q. In a food chain, which of the following is the correct order of energy flow? (2021)
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A.
Producer → Consumer → Decomposer
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B.
Consumer → Producer → Decomposer
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C.
Decomposer → Producer → Consumer
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D.
Producer → Decomposer → Consumer
Solution
The correct order of energy flow in a food chain is Producer → Consumer → Decomposer.
Correct Answer: A — Producer → Consumer → Decomposer
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Q. In a galvanic cell, if the anode reaction is 2Ag⁺ + 2e⁻ → 2Ag, what is the cathode reaction? (2022)
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A.
Cu²⁺ + 2e⁻ → Cu
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B.
Zn²⁺ + 2e⁻ → Zn
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C.
Fe²⁺ + 2e⁻ → Fe
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D.
Pb²⁺ + 2e⁻ → Pb
Solution
The cathode reaction must be a reduction reaction, and Cu²⁺ + 2e⁻ → Cu is a common cathode reaction.
Correct Answer: A — Cu²⁺ + 2e⁻ → Cu
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Q. In a galvanic cell, if the anode reaction is 2H₂ → 4H⁺ + 4e⁻, what is the cathode reaction?
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A.
O₂ + 4e⁻ + 4H⁺ → 2H₂O
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B.
2H₂O + 4e⁻ → 2H₂ + O₂
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C.
4H⁺ + 4e⁻ → 2H₂
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D.
2H₂ + O₂ → 2H₂O
Solution
The cathode reaction is O₂ + 4e⁻ + 4H⁺ → 2H₂O.
Correct Answer: A — O₂ + 4e⁻ + 4H⁺ → 2H₂O
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Q. In a galvanic cell, if the anode reaction is Ag⁺ + e⁻ → Ag, what is the cathode reaction?
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A.
Cu²⁺ + 2e⁻ → Cu
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B.
Zn²⁺ + 2e⁻ → Zn
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C.
Fe²⁺ + 2e⁻ → Fe
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D.
Pb²⁺ + 2e⁻ → Pb
Solution
The cathode reaction must be a reduction; Ag⁺ + e⁻ → Ag is the anode reaction.
Correct Answer: A — Cu²⁺ + 2e⁻ → Cu
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Q. In a galvanic cell, if the anode reaction is Zn → Zn²⁺ + 2e⁻, what is the cathode reaction if the cathode is Cu²⁺ + 2e⁻ → Cu?
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A.
Cu → Cu²⁺ + 2e⁻
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B.
Zn²⁺ + 2e⁻ → Zn
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C.
Zn + Cu²⁺ → Zn²⁺ + Cu
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D.
Cu²⁺ + 2e⁻ → Cu
Solution
The cathode reaction is Cu²⁺ + 2e⁻ → Cu.
Correct Answer: D — Cu²⁺ + 2e⁻ → Cu
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Q. In a group of 50 people, 20 are smokers. What is the probability of selecting a non-smoker? (2022)
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A.
2/5
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B.
3/5
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C.
1/2
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D.
1/4
Solution
Number of non-smokers = 50 - 20 = 30. Probability = 30/50 = 3/5.
Correct Answer: B — 3/5
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Q. In a group of 50 people, 20 are smokers. What is the probability that a randomly selected person is a non-smoker? (2021)
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A.
1/2
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B.
3/5
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C.
2/5
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D.
1/5
Solution
There are 50 - 20 = 30 non-smokers. The probability is 30/50 = 3/5.
Correct Answer: B — 3/5
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Q. In a harmonic oscillator, if the mass is doubled while keeping the spring constant the same, how does the frequency change? (2021)
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A.
Increases
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B.
Decreases
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C.
Remains the same
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D.
Becomes zero
Solution
Frequency (f) = (1/2π)√(k/m). If mass (m) is doubled, frequency decreases.
Correct Answer: B — Decreases
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Q. In a heat engine, if the input heat is 500 J and the work done is 300 J, what is the efficiency? (2023) 2023
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A.
60%
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B.
50%
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C.
40%
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D.
70%
Solution
Efficiency (η) = Work done / Input heat = 300 J / 500 J = 0.6 or 60%.
Correct Answer: A — 60%
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Q. In a lottery, there are 10 tickets, and 2 are winning tickets. What is the probability of picking a winning ticket?
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A.
1/5
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B.
1/10
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C.
1/2
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D.
2/10
Solution
Probability = Number of winning tickets / Total tickets = 2/10 = 1/5.
Correct Answer: A — 1/5
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Q. In a lottery, there are 10 tickets, and 3 are winning tickets. What is the probability of picking a winning ticket? (2022)
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A.
1/3
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B.
1/4
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C.
1/5
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D.
1/2
Solution
Probability = Number of winning tickets / Total tickets = 3/10.
Correct Answer: A — 1/3
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Q. In a measurement, if the error is systematic, what can be said about the results? (2020)
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A.
They are random
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B.
They are biased
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C.
They are accurate
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D.
They are precise
Solution
Systematic errors lead to biased results, consistently deviating from the true value.
Correct Answer: B — They are biased
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Q. In a measurement, if the uncertainty is ±0.5 cm, what is the range of the measurement 10.0 cm? (2023)
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A.
9.5 cm to 10.5 cm
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B.
9.0 cm to 11.0 cm
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C.
10.0 cm to 10.5 cm
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D.
10.0 cm to 11.0 cm
Solution
The range is calculated as (10.0 - 0.5) cm to (10.0 + 0.5) cm, which is 9.5 cm to 10.5 cm.
Correct Answer: A — 9.5 cm to 10.5 cm
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Q. In a p-n junction, what happens when the junction is forward biased? (2019)
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A.
Depletion region widens
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B.
Depletion region narrows
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C.
No current flows
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D.
Reverse current increases
Solution
When a p-n junction is forward biased, the depletion region narrows, allowing current to flow.
Correct Answer: B — Depletion region narrows
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Q. In a p-n junction, which type of charge carriers are majority carriers in the p-type region? (2019)
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A.
Electrons
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B.
Holes
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C.
Protons
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D.
Neutrons
Solution
In the p-type region of a p-n junction, holes are the majority charge carriers.
Correct Answer: B — Holes
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Q. In a parallel circuit with two resistors of 6Ω and 3Ω, what is the total current if a 12V battery is connected? (2021)
Solution
First, find the equivalent resistance: 1/R_eq = 1/6 + 1/3 = 1/2, so R_eq = 2Ω. Then, I = V/R_eq = 12V / 2Ω = 6A.
Correct Answer: C — 6A
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Q. In a parallel circuit with two resistors of 6Ω and 3Ω, what is the total resistance? (2019)
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A.
2Ω
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B.
4Ω
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C.
1.5Ω
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D.
9Ω
Solution
Using the formula 1/R_eq = 1/R1 + 1/R2, we get 1/R_eq = 1/6 + 1/3 = 1/6 + 2/6 = 3/6, thus R_eq = 2Ω.
Correct Answer: B — 4Ω
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Q. In a parallel circuit, if one branch has a resistance of 4Ω and another has 8Ω, what is the equivalent resistance? (2020)
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A.
2.67Ω
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B.
3Ω
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C.
4Ω
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D.
6Ω
Solution
1/R_eq = 1/4 + 1/8 = 2/8 + 1/8 = 3/8, so R_eq = 8/3Ω ≈ 2.67Ω.
Correct Answer: A — 2.67Ω
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Q. In a parallel RLC circuit, if R = 50 ohms, L = 0.2H, and C = 50μF, what is the total admittance? (2023)
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A.
0.02 S
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B.
0.04 S
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C.
0.06 S
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D.
0.08 S
Solution
Y = 1/R + j(ωC - 1/ωL); calculate Y for given values.
Correct Answer: C — 0.06 S
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Q. In a parallel RLC circuit, if R = 50Ω, L = 0.2 H, and C = 50μF, what is the quality factor Q? (2015)
Solution
Quality factor Q = (1/R) * √(L/C) = (1/50) * √(0.2/50e-6) = 2.
Correct Answer: B — 2
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Q. In a pedigree chart, a filled circle represents which of the following? (2023)
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A.
Male
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B.
Female
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C.
Affected female
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D.
Affected male
Solution
In a pedigree chart, a filled circle represents an affected female.
Correct Answer: C — Affected female
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Q. In a PN junction diode, what happens when it is forward biased? (2019)
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A.
Depletion region widens
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B.
Depletion region narrows
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C.
No current flows
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D.
Reverse current increases
Solution
When a PN junction diode is forward biased, the depletion region narrows, allowing current to flow.
Correct Answer: B — Depletion region narrows
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Q. In a PN junction, what is formed at the junction of p-type and n-type materials? (2021)
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A.
Electric field
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B.
Magnetic field
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C.
Thermal field
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D.
Gravitational field
Solution
An electric field is formed at the junction of p-type and n-type materials due to the diffusion of charge carriers.
Correct Answer: A — Electric field
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Q. In a predator-prey relationship, what is the primary effect of an increase in the prey population? (2021)
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A.
Decrease in predator population
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B.
Increase in predator population
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C.
Decrease in prey population
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D.
No effect on predator population
Solution
An increase in the prey population typically leads to an increase in the predator population due to more available food.
Correct Answer: B — Increase in predator population
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Q. In a predator-prey relationship, which of the following is true? (2022)
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A.
Predators are always larger than their prey.
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B.
Prey populations are always larger than predator populations.
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C.
Predators help control prey populations.
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D.
Prey can never escape predators.
Solution
Predators help control the population of prey species, maintaining a balance in the ecosystem.
Correct Answer: C — Predators help control prey populations.
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