Hydrogen (Basics) (Old NCERT) - Free MCQ Practice Test with solutions,

The most abundant element in the universe is dihydrogen, it comprises of 70% of the total mass of the universe. It is the principal element in the Solar atmosphere Jupiter and Saturn almost consists mostly of hydrogen.

Hydrogen exists in the form of three isotopes namely protium, deuterium and tritium. The atomic numbers of all the three isotopes of Hydrogen are same i.e. 1, but their symbols, relative atomic mass, density, etc vary.

Among the three isotopes of Hydrogen; protium, deuterium and tritium, a radioactive isotope is tritium and it emits beta rays and its half-life is 12.33 year. The other two isotopes protium deuterium are non Radioactive.

The density of tritium is greater than that of deuterium and the density of deuterium is greater than that of protium. The density of protium is 0.09, the density of deuterium 0.18 and density of tritium is 0.27.

Tritium has the greatest relative atomic mass than that of deuterium and protium. The relative atomic mass of protium, deuterium, and tritium are 1.0078, 2.0141 and 3.016 respectively. They do not have equal mass.

The boiling points of tritium are greater than that of deuterium and that is greater than that of hydrogen. The boiling points in kelvin of hydrogen, deuterium, and tritium are respectively 20.39, 23.67 and 25.

Deuterium is one of the two stable isotopes of Hydrogen (the other one being the protium), it is known as heavy hydrogen as it has one neutron and one proton. The radioactive isotope of hydrogen is tritium.

Molecular hydrogen in presence of electric Arc is converted into atomic hydrogen. The enthalpy change for the reaction is 105.4 kcal/mol. This newly formed atomic hydrogen is very reactive and its half-life period is 0.33 seconds.

The mixture of carbon monoxide and hydrogen produced by a synthetic gas is known as water gas. This is from the water gas shift reaction, which was created by a physicist from Italy. Water gas is made by blowing steam through white-hot coke.

As the mixture of carbon monoxide and hydrogen is used for the synthesis of methanol and a number of Hydrocarbons, it is called synthesis gas or syngas. The process of reducing syngas from coal is known as coal gasification.

At 773 Kelvin in the presence of ferric oxide and chromium oxide, the water gas (carbon monoxide and hydrogen) along with steam is transformed into carbon dioxide and hydrogen. This is also known as bosch process.

In Lane’s process from superheated steam, iron filings are passed over and heated to about 1023 to 1073 Kelvin when hydrogen is formed. The concerned reaction is 3Fe + 4H₂O → Fe₃O₄ + 4H₂ at 1023-1073 K.

When zinc is reacted with sodium hydroxide in the presence of heat Sodium zincate and hydrogen are formed the chemical formula of sodium zincate is Na₂ZnO₂. Therefore Sodium Zincate is made of sodium, zinc, and oxygen.

Highly pure dihydrogen (H₂) that is greater than 99.95% is obtained by electrolysis in warm aqueous barium hydroxide (BaOH_(aq)) solution between Nickel electrodes (Ni). This is one of the processes of commercial production of hydrogen.

A Brine solution is nothing but water that has dissolved salt in it hydrogen is obtained as a byproduct in the manufacture of sodium hydroxide and chlorine by the electrolysis of brine solution (salt water).

Physical properties of dihydrogen include that it is colourless, odourless, tasteless, combustible gas. It is lighter than air and insoluble in water and is also neutral to Litmus. Therefore heavier than air is not a property of dihydrogen.

At 970 Kelvin, an electric discharge 2 moles of hydrogen molecule combines with one mole of Oxygen in order to form 2 moles of water. This has an enthalpy change of about 285.9 KJ/mol, the enthalpy change is negative for the above process.

The order of reactivity of halogens with hydrogen is that Fluorine’s reactivity is greater than that of chlorine and chlorine’s reactivity is greater than that of bromine and bromine’s reactivity is greater than that of Iodine.

At 673 Kelvin and 200 atmospheric pressure, one mole of nitrogen combines with three moles of hydrogen in presence of iron and molybdenum in order to form 2 moles of ammonia and the enthalpy change is 92.6 KJ per Mol, the enthalpy here change is negative.

In the formation of 2 moles of sodium hydride from two moles of sodium and one mole of hydrogen, the hydrogen acts as an oxidising agent. An oxidizing agent gains electrons from the other molecule and reduces itself.