Important MCQs on Hydrogen with Explanation

Ans. (d) Oxygen

Explanation: Brine solution is the concentrated solution of sodium chloride in the water. As electricity passes through the electrodes, chlorine gas is released from the anode and used as a disinfectant in the swimming pool while hydrogen gas is released from the cathode which helps in the production of ammonium. Sodium hydroxide remains in the solution and is used for manufacturing soaps in industry. Therefore, oxygen is not produced in the process of electrolysis of brine solution.

Ans. (b) Liquid

Explanation: A liquid state is required for conducting electricity during electrolysis. It is so because electrolysis requires the movement of ions present in electrolytes in the molten or dissolved state. While in solids conduction of electricity takes place through electrons, not ions.

Ans. (a) Loss of hydrogen

Explanation: Oxidation is the state in which an atom loses hydrogen, gains oxygen, and loses electrons. While the reduction in the state when an atom gains hydrogen loses oxygen and gains electrons. We can understand this concept by taking the equation

2Mg + O₂→2MgO

In the equation above, Magnesium is oxidized by gaining oxygen or by losing electrons.

Now let's look at the equation to understand the concept of reduction. 

ZnO →Zn + O₂

Here in the reaction, the Zinc oxide compound decomposes to give zinc and oxygen. This shows that zinc oxide is reduced to zinc by losing oxygen. 

Ans. (d) Sodium Hydroxide 

Explanation: Among the given options, urea, glucose, and benzene are termed nonelectrolytes as these are organic compounds and do not dissociate into ions in solutions, hence do not conduct electricity in electrolysis. While electrolysis, the movement of ions is important to facilitate the conduction of electricity through the electrodes.

Ans. (b) Liquid

Explanation: Pure Hydrogen peroxide is found in a liquid state. It is slightly pale blue. It is non-planar with an open book structure, with O-O bond length of approximately 145 pm and that of O-H is 98.8 pm. Hydrogen peroxide is used for bleaching, and cleaning purposes.

Ans. (b) D₂O

Explanation: Nuclear reactors harness a lot of energy due to the continuous fission of uranium along with the release of neutron particles. Heavy Water is used as a modulator to slow down the neutron, to further break other atoms. Hence heavy Water keeps the reaction going without much absorption of neutrons. Deuterium is known as heavy water. Deuterium is widely used for medicinal, industrial, and commercial purposes. 

Ans. (b) Ca(OH)₂

Explanation: Due to Magnesium bicarbonate and calcium bicarbonate, the hardness of water exists. When soap is mixed with hard water, it results in the formation of a white layer called scum instead of lather. Calcium hydroxide is known as Clark's Reagent. Calcium hydroxide helps in the conversion of bicarbonates and carbonates, which are insoluble, and can be filtered away. An additional method for the removal of hardening of water includes the ion exchange method, by using chelating agents.

Ans. (d) All of these

Explanation: Zeolite is used in the process of softening hard water. It is porous. It removes temporary as well as permanent hardening of water. Such a process is said to be called the zeolite softening process. Natural zeolite (gluconate), as well as synthetic Zeolite (permutit), could be used to soften hard water. Apart from softening hard water, zeolite is widely used in chemical reactions as catalysts and as a gas separator. Also used in the production of hydrocarbons. It also helps in the exchange of ions in detergent.

Ans. (c) 3

Explanation: Hydrogen has three isotopes, named protium, deuterium, and tritium. All these isotopes have an identical number of protons, i. e 1. However, these isotopes differ in the number of neutrons. protium has no neutron,1 electron, and 1 proton. Deuterium has 1 proton, 1 neutron, and 1 electron. Tritium has 2 neutrons, 1 proton, and 1 electron.

Ans. (a) Ca²⁺ and Mg²⁺

Explanation: The hardness of water is due to the presence of ions like calcium and magnesium ions. The salts of chlorine and sulphate of calcium and magnesium result in the permanent hardness of water, and the presence of salts of bicarbonate causes temporary hardness of the water.

Ans. (d) Decomposed by H₂SO₄ 

Explanation: When moist hydrogen peroxide dried over H₂SO₄, the following reaction will take place:- 

H₂O₂ + [O] → H₂O + O₂

Ans. (c) Ability to gain an electron to attain noble gas configuration. 

Explanation: To attain a stable gas configuration, hydrogen has a tendency to quickly take an electron and complete its helium gas configuration, that is two electrons in its outermost /valance shell.

Ans. (c) 3.8°C 

Explanation: Heavy Water is made up of deuterium and oxygen together. Deuterium is the isotope of hydrogen with the number of electrons equal to the number of neutrons. Water with hydrogen freezes at 0°C, which is lower than the freezing point of heavy water.

Ans. (c) 0°C - 4°C 

Explanation: The water shows anomalous behavior when the temperature goes down from 4°C to 0°C. As the temperature goes down, the water expands instead of contracting. Due to this, the density of water seems to be maximum at 4°C.