Ionization energy generally decreases down a group because: MCQ with Answer and Explanation

Ionization energy generally decreases down a group because:
A. Atomic radius increases and shielding effect increases
B. Number of valence electrons increases
C. Electron affinity increases
D. Nuclear charge decreases
Answer: Option A
Solution (By JKSSB Mock Tests)
Down a group, number of shells increases, atomic radius increases, and inner electrons shield the outermost electron from the nucleus. The effective nuclear charge experienced by valence electron decreases, making it easier to remove. Thus ionization energy decreases. For example, IE of Cs

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Question #1
During the extraction of aluminium by Hall-Héroult process, cryolite (Na₃AlF₆) is added to alumina to:
A. Prevent corrosion
B. Lower the melting point and increase conductivity
C. Increase the yield of aluminium
D. Act as catalyst

Correct Answer: Option B


Explanation:
Alumina has a very high melting point (~2050°C). Cryolite (and fluorspar) is mixed to form a molten mixture with lower melting point (~950°C) and better electrical conductivity, enabling electrolytic reduction. The electrolyte is a solution of alumina in molten cryolite. Carbon anodes are consumed. This reduces energy consumption.

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CNG is considered a cleaner fuel than diesel because:
A. It produces less CO₂ and negligible particulate matter
B. It is a liquid
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D. It is more expensive

Correct Answer: Option A


Explanation:
CNG (mainly methane) has a higher H/C ratio than diesel, so it emits less CO₂ per unit energy. It burns almost completely, producing very little carbon monoxide, unburnt hydrocarbons, and particulate matter (soot). It also contains negligible sulfur, thus no SO₂ emissions.

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Which of the following statements about a catalyst is incorrect?
A. It does not change the enthalpy of the reaction.
B. It initiates the reaction.
C. It remains unchanged in mass after the reaction.
D. It lowers the activation energy.

Correct Answer: Option B


Explanation:
A catalyst does not initiate a reaction; it only changes the rate of a reaction that is already thermodynamically feasible. It provides an alternative pathway with lower activation energy. It does not change the overall enthalpy (ΔH) or the equilibrium position, and it is recovered unchanged in mass.

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