Question 1

Which of the following statements is false regarding hydrogen ?

Accepted Answer

Hydrogen has three isotopes: Protium (^ 1 H), Deuterium (^ 2 H), and Tritium (^ 3 H). Thus, the statement that it has two isotopes is false. Hydrogen is placed separately in the periodic table due to its anomalous behavior, resembling both alkali metals and halogens. A hydrogen atom consists of one proton and one electron. When it loses its only electron, it forms an H^ + ion, which is a bare proton. Atomic hydrogen is highly reactive and does not exist freely in nature; it exists as a diatomic

Question 2

Which of the following statements is NOT correct regarding dihydrogen?

Accepted Answer

Dihydrogen (H_2) is a homonuclear diatomic molecule, meaning both atoms have the same electronegativity. Therefore, it is a non-polar molecule. Since water is a polar solvent, dihydrogen is practically insoluble in water due to the "like dissolves like" principle. Dihydrogen is a colorless, odorless, and tasteless gas. It is lighter than air and burns with a pale blue flame. Thus, the statement that it is a polar water-soluble gas is incorrect. Answer: It is a polar water-soluble gas.

Question 3

What is the role of glycerol in the decomposition of hydrogen peroxide?

Accepted Answer

Hydrogen peroxide (H_2O_2) decomposes into water and oxygen gas upon standing or heating. To prevent or slow down this decomposition, certain substances are added which act as negative catalysts (inhibitors). Glycerol, along with urea and acetanilide, is commonly used as a stabilizer for hydrogen peroxide. It acts as a negative catalyst and retards the decomposition process. Therefore, glycerol reduces the reaction rate of the decomposition of hydrogen peroxide. Answer: It reduces the reaction r

Question 4

The most abundant element in the universe is

Accepted Answer

Hydrogen is the most abundant element in the universe, accounting for approximately 75\% of its normal matter by mass. Helium is the second most abundant element. Answer: Hydrogen

Question 5

Which of the following is the most abundant element in universe?

Accepted Answer

Hydrogen ( H ) is the most abundant element in the universe, accounting for approximately 75\% of its normal matter by mass. Helium is the second most abundant element, followed by oxygen. Therefore, H is the most abundant element among the given options. Answer: H

Question 6

Which of the following ions are responsible for hardness of water?

Accepted Answer

Hardness of water is primarily caused by the presence of soluble salts of calcium and magnesium, such as their bicarbonates, chlorides, and sulfates. Therefore, Ca ^ 2+ and Mg ^ 2+ ions are responsible for the hardness of water. Answer: Ca ^ 2+ and Mg ^ 2+ ions.

Question 7

Which of the following is obtained when dihydrogen reacts with the alkali metals at high temperature?

Accepted Answer

Alkali metals react with dihydrogen at high temperatures to form the corresponding metal hydrides. 2M + H_2 2M^ + H^ - where M represents an alkali metal (Li, Na, K, Rb, Cs). These hydrides are ionic (salt-like) in nature. Answer: Metal hydrides

Hydrogen — Previous Year Questions & Solutions