This set of Class 11 Chemistry Chapter 9 Multiple Choice Questions & Answers (MCQs) focuses on “Dihydrogen & H2”.
1. How much percent of the total mass of the Universe is dihydrogen?
Explanation: 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.
2. Which of the following is not an isotope of hydrogen?
Explanation: 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.
3. Which of the following is Radioactive?
Explanation: 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.
4. Protium has a greater relative abundance than tritium.
Explanation: Yes, the above statement is true because protium has a relative abundance greater than that of tritium. The relative abundance of protium is 99.98%, the relative abundance of deuterium as 0.0156% and tritium is 10-15%.
5. Which of the following statements is true regarding the density of isotopes of the hydrogen?
a) protium’s density is greater than that of tritium
b) tritium’s density is greater than that of deuterium
c) deuterium’s density is greater than that of tritium
d) protium’s density is greater than that of deuterium
Explanation: 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.
6. Which of the following as a greatest relative atomic mass?
d) all have equal mass
Explanation: 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.
7. Deuterium has a melting point higher than that of hydrogen.
Explanation: The above statement is true because deuterium has a greater boiling point than that of hydrogen and tritium has a greater boiling point than that of deuterium. The boiling points of tritium, deuterium, and protium are 20.62, 18.73 and 13.96 in Kelvin respectively.
8. Which of the following option is true regarding the boiling point of hydrogen isotopes?
a) all three isotopes have an equal boiling point
b) deuterium has a greater boiling point than tritium
c) tritium has a greater boiling point than that of protium
d) protium has a higher boiling point than that of tritium
Explanation: 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.
9. Deuterium is also known as _________
a) dark hydrogen
b) heavy hydrogen
c) light hydrogen
d) radioactive hydrogen
Explanation: 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.
10. What is the half-life of atomic hydrogen?
Explanation: 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.
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