What happens to atomic size and nuclear charge across a period, and what is the effect on electropositivity? What gases remain after passing air through alkaline pyrogallol and quicklime? Why does wat

Here are the solutions to the questions:

40. A decrease in atomic size and an increase in nuclear charge across a period lead to

• Across a period, the effective nuclear charge increases and the atomic radius decreases. This results in a stronger attraction between the nucleus and the valence electrons. Consequently, it becomes harder to remove electrons and easier to attract them.
• This leads to a decrease in the tendency to lose electrons, which means a decrease in electropositivity.
• The correct option is (c) a decrease in electropositivity.

41. When Air which contains the gases oxygen, nitrogen, carbon dioxide, water vapor and the rare gases is passed through alkaline pyrogallol and then over quicklime, the only gases left are

• Alkaline pyrogallol absorbs oxygen.
• Quicklime (calcium oxide) absorbs acidic gases like carbon dioxide and water vapor.
• After these two steps, nitrogen and the unreactive rare gases (like argon) are the only components of air that remain.
• The correct option is (D) Nitrogen and the rare gases.

42. A gas jar was inverted over burning yellow phosphorus floating over water in a trough. The water level rises because

• Burning yellow phosphorus reacts with oxygen in the air to form solid phosphorus pentoxide ($P_4O_{10}$).
• This reaction consumes the oxygen gas inside the jar, leading to a decrease in the volume of gas and thus a reduction in pressure.
• The external atmospheric pressure then pushes the