Question

When radioactive minerals like cleveite , monazite and pitchblende are heated to 1273K in a vacuum , the noble gas obtained is:
A. Rn
B. Kr
C. He
D. Ne

Answer 1

Hint:
We know that radioactivity is the process in which particles from nuclei which results in the stability of the nuclei. There are three types of radioactivity , they are alpha, beta and gamma emission.

Complete step by step answer:
As we know that cleveite is an impure radioactive mineral which contains uranium in it.The chemical formula of cleveite is $U{O}_2$. Monazite is a phosphate mineral which contains rare earth metals. It is reddish brown in colour. The chemical formula of Monazite is $P{O}_{4}Si{O}_4$. Pitchblende is a radioactive mineral or ore which is rich in uranium . Pitchblende is a variety of Uraninite. Because of the radioactivity nature of the pitchblende it contains traces of lead and helium. The chemical formula of pitchblende is $U{O}_2$. So whenever we heat the radioactive minerals like cleveite , monazite and pitchblende at $1273K$ in a vacuum, Helium gas is obtained. This is because during alpha emission , helium gas is entrapped in the radioactive minerals like cleveite , monazite and pitchblende.
So from the above explanation and discussion it is clear to us that the correct answer of the given question is option: C. $He$

Additional information: Helium gas is a noble gas . The atomic number of helium is two and the mass number of helium is four. It has two electrons and protons. It’s boiling point is very low. It is odourless, tasteless and non toxic in nature. It is a monatomic gas .

Note: Always remember that whenever we heat radioactive minerals like cleveite , monazite and pitchblende at $1273K$, helium gas is obtained . Helium gas is a noble gas . It is said to be a noble gas because it is very less reactive in nature.