Major Competitive Exams
Q. What is the speed of sound in air at 20°C?
A.
343 m/s
B.
330 m/s
C.
300 m/s
D.
350 m/s
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Solution
The speed of sound in air at 20°C is approximately 343 m/s.
Correct Answer: A — 343 m/s
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Q. What is the speed of sound in air at room temperature (20°C)?
A.
343 m/s
B.
300 m/s
C.
1500 m/s
D.
1200 m/s
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Solution
The speed of sound in air at 20°C is approximately 343 m/s.
Correct Answer: A — 343 m/s
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Q. What is the spin quantum number (m_s) for an electron in an orbital?
A.
0
B.
+1/2
C.
-1/2
D.
1
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Solution
The spin quantum number can be +1/2 or -1/2 for an electron in an orbital.
Correct Answer: B — +1/2
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Q. What is the spin quantum number (m_s) for an electron with a clockwise spin?
A.
-1/2
B.
0
C.
+1/2
D.
1
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Solution
The spin quantum number (m_s) is +1/2 for an electron with clockwise spin.
Correct Answer: C — +1/2
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Q. What is the spin quantum number (m_s) for an electron?
A.
0
B.
+1/2
C.
-1/2
D.
Both +1/2 and -1/2
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Solution
The spin quantum number (m_s) can be +1/2 or -1/2 for an electron.
Correct Answer: D — Both +1/2 and -1/2
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Q. What is the square of the modulus of the complex number 1 + 2i? (2014)
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Solution
The modulus is √(1^2 + 2^2) = √(1 + 4) = √5. The square of the modulus is 5.
Correct Answer: A — 5
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Q. What is the square of the modulus of the complex number 1 + i? (2020)
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Solution
The modulus is √(1^2 + 1^2) = √2, and the square of the modulus is 2.
Correct Answer: A — 2
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Q. What is the square root of 64? (2020)
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Solution
The square root of 64 is 8.
Correct Answer: C — 8
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Q. What is the standard acceleration due to gravity in m/s²?
A.
9.8
B.
10
C.
9.81
D.
9.75
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Solution
The standard acceleration due to gravity is approximately 9.81 m/s².
Correct Answer: C — 9.81
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Q. What is the standard deviation of the data set {10, 12, 23, 23, 16, 23, 21, 16}?
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Solution
Mean = 19.5, Variance = 25, Standard Deviation = √25 = 5.
Correct Answer: A — 5
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Q. What is the standard deviation of the data set {10, 12, 23, 23, 16, 23, 21}?
A.
5.5
B.
4.5
C.
6.5
D.
3.5
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Solution
Mean = 19.14, Variance = 20.25, Standard Deviation = √20.25 = 4.5.
Correct Answer: B — 4.5
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Q. What is the standard deviation of the data set {4, 8, 6, 5, 3}?
A.
1.58
B.
2.58
C.
3.58
D.
4.58
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Solution
Mean = 5.2. Variance = [(4-5.2)² + (8-5.2)² + (6-5.2)² + (5-5.2)² + (3-5.2)²]/5 = 6.56. Standard Deviation = √6.56 ≈ 2.56.
Correct Answer: B — 2.58
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Q. What is the standard deviation of the data set: 1, 2, 3, 4, 5?
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Solution
Mean = 3. Standard Deviation = sqrt[((1-3)^2 + (2-3)^2 + (3-3)^2 + (4-3)^2 + (5-3)^2)/5] = sqrt[2] = 1.414.
Correct Answer: A — 1
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Q. What is the standard electrode potential of the half-reaction Zn²⁺ + 2e⁻ → Zn?
A.
0.76 V
B.
0.34 V
C.
-0.76 V
D.
-0.34 V
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Solution
The standard electrode potential for Zn²⁺/Zn is -0.76 V.
Correct Answer: C — -0.76 V
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Q. What is the standard electrode potential of the hydrogen electrode?
A.
0.00 V
B.
0.34 V
C.
1.23 V
D.
0.76 V
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Solution
The standard electrode potential of the hydrogen electrode is defined as 0.00 V.
Correct Answer: A — 0.00 V
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Q. What is the standard electrode potential of the hydrogen electrode? (2023) 2023
A.
0 V
B.
1 V
C.
2 V
D.
0.5 V
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Solution
The standard electrode potential of the hydrogen electrode is defined as 0 V.
Correct Answer: A — 0 V
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Q. What is the standard enthalpy change (ΔH°) for the formation of water from its elements? (2022)
A.
-285.83 kJ/mol
B.
0 kJ/mol
C.
285.83 kJ/mol
D.
-241.82 kJ/mol
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Solution
The standard enthalpy change for the formation of water from its elements (H2 and O2) is -285.83 kJ/mol.
Correct Answer: A — -285.83 kJ/mol
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Q. What is the standard enthalpy change (ΔH°) for the reaction: C(s) + O2(g) → CO2(g)? (2022)
A.
It is always positive.
B.
It is always negative.
C.
It can be zero.
D.
It depends on the temperature.
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Solution
The standard enthalpy change for combustion reactions, such as the formation of CO2 from carbon and oxygen, is typically negative, indicating that the reaction is exothermic.
Correct Answer: B — It is always negative.
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Q. What is the standard enthalpy change for the formation of a compound?
A.
ΔHf
B.
ΔHc
C.
ΔHrxn
D.
ΔHsol
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Solution
The standard enthalpy change for the formation of a compound is denoted as ΔHf.
Correct Answer: A — ΔHf
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Q. What is the standard enthalpy change for the formation of an element in its standard state?
A.
Zero
B.
Positive
C.
Negative
D.
Depends on the element
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Solution
The standard enthalpy change for the formation of an element in its standard state is defined as zero.
Correct Answer: A — Zero
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Q. What is the standard enthalpy change for the formation of water from its elements?
A.
-285.83 kJ/mol
B.
-241.82 kJ/mol
C.
-393.5 kJ/mol
D.
-572.4 kJ/mol
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Solution
The standard enthalpy change for the formation of water (H2 + 1/2 O2 -> H2O) is -285.83 kJ/mol.
Correct Answer: A — -285.83 kJ/mol
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Q. What is the standard enthalpy change for the reaction 2H2 + O2 → 2H2O if the enthalpy of formation of H2O is -285.8 kJ/mol?
A.
-571.6 kJ
B.
-285.8 kJ
C.
0 kJ
D.
285.8 kJ
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Solution
ΔH = 2 * (-285.8 kJ) = -571.6 kJ
Correct Answer: A — -571.6 kJ
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Q. What is the standard enthalpy change for the reaction 2H2(g) + O2(g) → 2H2O(l)?
A.
-285.83 kJ/mol
B.
-241.82 kJ/mol
C.
-572.4 kJ/mol
D.
-1000 kJ/mol
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Solution
The standard enthalpy of formation of water is -241.82 kJ/mol.
Correct Answer: B — -241.82 kJ/mol
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Q. What is the standard enthalpy change for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) if ΔHf°(NH3) = -45.9 kJ/mol?
A.
-91.8 kJ
B.
0 kJ
C.
45.9 kJ
D.
91.8 kJ
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Solution
ΔH = 2 * ΔHf°(NH3) = 2 * (-45.9) = -91.8 kJ
Correct Answer: A — -91.8 kJ
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Q. What is the standard enthalpy change for the reaction: C(s) + O2(g) → CO2(g) if ΔHf° for CO2 is -393.5 kJ/mol?
A.
-393.5 kJ
B.
0 kJ
C.
393.5 kJ
D.
None of the above
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Solution
The standard enthalpy change is equal to the enthalpy of formation of CO2, which is -393.5 kJ.
Correct Answer: A — -393.5 kJ
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Q. What is the standard enthalpy change of formation for a substance?
A.
The enthalpy change when one mole of a compound is formed from its elements in their standard states.
B.
The enthalpy change when one mole of a substance is completely burned in oxygen.
C.
The enthalpy change when one mole of a substance is dissolved in water.
D.
The enthalpy change when one mole of a gas is compressed to a smaller volume.
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Solution
The standard enthalpy change of formation is defined as the enthalpy change when one mole of a compound is formed from its elements in their standard states.
Correct Answer: A — The enthalpy change when one mole of a compound is formed from its elements in their standard states.
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Q. What is the standard enthalpy change of formation for an element in its standard state?
A.
0 kJ/mol
B.
100 kJ/mol
C.
298 kJ/mol
D.
1 kJ/mol
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Solution
The standard enthalpy change of formation for an element in its standard state is defined as 0 kJ/mol.
Correct Answer: A — 0 kJ/mol
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Q. What is the standard enthalpy change of formation for elements in their standard state?
A.
0 kJ/mol
B.
100 kJ/mol
C.
298 kJ/mol
D.
1 kJ/mol
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Solution
The standard enthalpy change of formation for elements in their standard state is defined as zero.
Correct Answer: A — 0 kJ/mol
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Q. What is the standard enthalpy change of formation for water (H2O) at 25°C?
A.
-285.83 kJ/mol
B.
-241.82 kJ/mol
C.
-393.5 kJ/mol
D.
-241.0 kJ/mol
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Solution
The standard enthalpy change of formation for water at 25°C is -241.82 kJ/mol.
Correct Answer: B — -241.82 kJ/mol
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Q. What is the standard enthalpy of formation for an element in its standard state?
A.
0 kJ/mol
B.
100 kJ/mol
C.
298 kJ/mol
D.
1 kJ/mol
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Solution
The standard enthalpy of formation for an element in its standard state is defined as 0 kJ/mol.
Correct Answer: A — 0 kJ/mol
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