Q. What is the electronic configuration of oxygen?
A.
1s2 2s2 2p4
B.
1s2 2s2 2p6
C.
1s2 2s2 2p2
D.
1s2 2s2 2p5
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Solution
Oxygen has 8 electrons, and its electronic configuration is 1s2 2s2 2p4.
Correct Answer: A — 1s2 2s2 2p4
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Q. What is the electronic configuration of the chloride ion (Cl-)?
A.
1s2 2s2 2p6 3s2 3p5
B.
1s2 2s2 2p6 3s2 3p6
C.
1s2 2s2 2p6 3s2 3p4
D.
1s2 2s2 2p6 3s2 3p3
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Solution
Chloride ion has gained one electron, making its configuration 1s2 2s2 2p6 3s2 3p6.
Correct Answer: B — 1s2 2s2 2p6 3s2 3p6
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Q. What is the electronic configuration of the element with atomic number 12?
A.
[Ne] 3s2
B.
[He] 2s2 2p6
C.
[Ne] 3s1
D.
[Ar] 4s2
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Solution
The element with atomic number 12 is magnesium (Mg), and its electronic configuration is [Ne] 3s2.
Correct Answer: A — [Ne] 3s2
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Q. What is the electronic configuration of the element with atomic number 15?
A.
[Ne] 3s2 3p3
B.
[Ne] 3s2 3p4
C.
[Ne] 3s2 3p5
D.
[Ne] 3s2 3p2
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Solution
The element with atomic number 15 is phosphorus (P), and its electronic configuration is [Ne] 3s2 3p3.
Correct Answer: A — [Ne] 3s2 3p3
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Q. What is the electronic configuration of the element with atomic number 17?
A.
1s2 2s2 2p6 3s2 3p5
B.
1s2 2s2 2p6 3s2 3p4
C.
1s2 2s2 2p6 3s2 3p6
D.
1s2 2s2 2p6 3s2 3p3
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Solution
Chlorine (Cl) has the configuration 1s2 2s2 2p6 3s2 3p5.
Correct Answer: A — 1s2 2s2 2p6 3s2 3p5
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Q. What is the electronic configuration of the element with atomic number 20?
A.
[Ne] 3s2 3p6
B.
[Ar] 4s2
C.
[He] 2s2 2p6 3s2 3p6
D.
[Ne] 3s2 3p4
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Solution
The element with atomic number 20 is Calcium, which has the configuration [Ar] 4s2.
Correct Answer: B — [Ar] 4s2
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Q. What is the electronic configuration of the element with atomic number 26?
A.
[Ar] 4s2 3d6
B.
[Ar] 4s2 3d5
C.
[Kr] 5s2 4d6
D.
[Ar] 4s1 3d7
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Solution
The element with atomic number 26 is iron (Fe), and its electronic configuration is [Ar] 4s2 3d6.
Correct Answer: A — [Ar] 4s2 3d6
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Q. What is the electronic configuration of the element with atomic number 29?
A.
[Ar] 4s2 3d9
B.
[Ar] 4s2 3d10
C.
[Kr] 5s1 4d10
D.
[Ne] 3s2 3p6
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Solution
Copper (Cu) has the configuration [Ar] 4s2 3d9.
Correct Answer: A — [Ar] 4s2 3d9
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Q. What is the electronic configuration of the iron (Fe) atom?
A.
[Ar] 4s2 3d6
B.
[Ar] 4s2 3d5
C.
[Ar] 4s1 3d7
D.
[Ar] 4s2 3d4
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Solution
Iron (Fe) has 26 electrons, and its electronic configuration is [Ar] 4s2 3d6.
Correct Answer: A — [Ar] 4s2 3d6
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Q. What is the electronic configuration of the nitrogen atom?
A.
1s2 2s2 2p3
B.
1s2 2s2 2p4
C.
1s2 2s2 2p2
D.
1s2 2s2 2p5
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Solution
Nitrogen has 7 electrons, and its electronic configuration is 1s2 2s2 2p3.
Correct Answer: A — 1s2 2s2 2p3
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Q. What is the electronic configuration of the potassium ion (K+)?
A.
1s2 2s2 2p6 3s2
B.
1s2 2s2 2p6
C.
1s2 2s2 2p6 3s1
D.
1s2 2s2 2p6 3s2 3p1
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Solution
The potassium ion (K+) loses one electron, resulting in the configuration 1s2 2s2 2p6.
Correct Answer: B — 1s2 2s2 2p6
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Q. What is the electronic configuration of the sodium ion (Na+)?
A.
1s2 2s2 2p6
B.
1s2 2s2 2p5
C.
1s2 2s2 2p4
D.
1s2 2s2 2p3
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Solution
Sodium ion (Na+) has lost one electron, resulting in the configuration 1s2 2s2 2p6.
Correct Answer: A — 1s2 2s2 2p6
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Q. What is the empirical formula of a compound containing 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass?
A.
CH2O
B.
C2H4O2
C.
C3H6O3
D.
C4H8O4
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Solution
Convert percentages to grams (assume 100 g total): 40 g C, 6.7 g H, 53.3 g O. Convert to moles: C=3.33, H=6.67, O=3.33. The simplest ratio is 1:2:1, giving CH2O.
Correct Answer: A — CH2O
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Q. What is the empirical formula of a compound containing 40% carbon, 6.7% hydrogen, and 53.3% oxygen?
A.
CH2O
B.
C2H4O2
C.
C3H6O3
D.
C4H8O4
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Solution
Converting percentages to moles gives C: 40/12 = 3.33, H: 6.7/1 = 6.7, O: 53.3/16 = 3.33. The simplest ratio is 1:2:1, giving the empirical formula CH2O.
Correct Answer: A — CH2O
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Q. What is the empirical formula of C6H12O6?
A.
C2H4O2
B.
CH2O
C.
C3H6O3
D.
C6H12O6
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Solution
The empirical formula is the simplest whole number ratio, which is CH2O.
Correct Answer: B — CH2O
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Q. What is the empirical formula of glucose (C6H12O6)?
A.
C6H12O6
B.
CH2O
C.
C3H6O3
D.
C2H4O2
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Solution
The empirical formula is the simplest whole number ratio of the elements in a compound. For glucose, it is CH2O.
Correct Answer: B — CH2O
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Q. What is the enthalpy change for the formation of 1 mole of CO2 from its elements in their standard states?
A.
-393.5 kJ/mol
B.
-285.8 kJ/mol
C.
0 kJ/mol
D.
100 kJ/mol
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Solution
The standard enthalpy of formation of CO2 is -393.5 kJ/mol.
Correct Answer: A — -393.5 kJ/mol
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Q. What is the enthalpy change for the formation of water from hydrogen and oxygen?
A.
It is positive.
B.
It is negative.
C.
It is zero.
D.
It is undefined.
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Solution
The formation of water from hydrogen and oxygen is an exothermic reaction, resulting in a negative enthalpy change.
Correct Answer: B — It is negative.
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Q. What is the enthalpy change for the reaction 2Na + Cl2 → 2NaCl?
A.
-411 kJ
B.
-240 kJ
C.
0 kJ
D.
411 kJ
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Solution
The enthalpy change for the formation of NaCl from its elements is -411 kJ.
Correct Answer: A — -411 kJ
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Q. What is the enthalpy change for the reaction at constant pressure?
A.
ΔH = ΔU + PΔV
B.
ΔH = ΔU - PΔV
C.
ΔH = ΔU + VΔP
D.
ΔH = ΔU - VΔP
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Solution
At constant pressure, the enthalpy change is given by ΔH = ΔU + PΔV.
Correct Answer: A — ΔH = ΔU + PΔV
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Q. What is the enthalpy change for the reaction N2(g) + 3H2(g) → 2NH3(g) at standard conditions?
A.
-92.4 kJ
B.
-45.9 kJ
C.
0 kJ
D.
0.5 kJ
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Solution
The standard enthalpy change for the formation of ammonia is -92.4 kJ.
Correct Answer: A — -92.4 kJ
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Q. What is the enthalpy change for the reaction: 2H2(g) + O2(g) → 2H2O(g)?
A.
It is positive.
B.
It is negative.
C.
It is zero.
D.
It is dependent on temperature.
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Solution
The formation of water from hydrogen and oxygen is an exothermic reaction, thus the enthalpy change is negative.
Correct Answer: B — It is negative.
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Q. What is the enthalpy change for the reaction: 2H2(g) + O2(g) → 2H2O(l)?
A.
-571.6 kJ
B.
-285.8 kJ
C.
0 kJ
D.
285.8 kJ
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Solution
The enthalpy change for the formation of 2 moles of water is -571.6 kJ.
Correct Answer: A — -571.6 kJ
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Q. What is the enthalpy change for the reaction: C(s) + O2(g) -> CO2(g)?
A.
-393.5 kJ/mol
B.
-241.8 kJ/mol
C.
0 kJ/mol
D.
285.8 kJ/mol
Show solution
Solution
The enthalpy change for the formation of CO2 from carbon and oxygen is -393.5 kJ/mol.
Correct Answer: A — -393.5 kJ/mol
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Q. What is the enthalpy change for the reaction: C(s) + O2(g) → CO2(g)?
A.
-393.5 kJ/mol
B.
-241.8 kJ/mol
C.
0 kJ/mol
D.
285.8 kJ/mol
Show solution
Solution
The enthalpy change for the formation of CO2 from its elements is -393.5 kJ/mol.
Correct Answer: A — -393.5 kJ/mol
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Q. What is the enthalpy change for the reaction: CaCO3(s) → CaO(s) + CO2(g)?
A.
It is an endothermic reaction.
B.
It is an exothermic reaction.
C.
It has no enthalpy change.
D.
It is spontaneous at all temperatures.
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Solution
The decomposition of calcium carbonate is an endothermic reaction, requiring heat input.
Correct Answer: A — It is an endothermic reaction.
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Q. What is the enthalpy change for the reaction: H2(g) + 1/2 O2(g) → H2O(l)?
A.
-285.8 kJ/mol
B.
0 kJ/mol
C.
-241.8 kJ/mol
D.
-572 kJ/mol
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Solution
The standard enthalpy change for the formation of water from its elements is -241.8 kJ/mol.
Correct Answer: C — -241.8 kJ/mol
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Q. What is the enthalpy change for the reaction: N2(g) + 3H2(g) → 2NH3(g)?
A.
It is always positive.
B.
It is always negative.
C.
It can be either positive or negative depending on conditions.
D.
It is zero.
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Solution
The formation of ammonia from nitrogen and hydrogen is an exothermic reaction, thus the enthalpy change is negative.
Correct Answer: B — It is always negative.
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Q. What is the enthalpy change when 1 mole of NaCl is dissolved in water?
A.
-3.87 kJ
B.
0 kJ
C.
+3.87 kJ
D.
-7.0 kJ
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Solution
The enthalpy change when 1 mole of NaCl is dissolved in water is approximately -3.87 kJ.
Correct Answer: A — -3.87 kJ
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Q. What is the enthalpy change when 1 mole of water vapor condenses to liquid water?
A.
It is positive.
B.
It is negative.
C.
It is zero.
D.
It is dependent on pressure.
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Solution
The condensation of water vapor to liquid water releases heat, making the enthalpy change negative.
Correct Answer: B — It is negative.
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