Tritium, symbol T, is hydrogen with a mass number of 3. It is radioactive and undergoes β
decay.
Which of the following could be the only product(s) after a quantity of HTO undergoes decay?
1 He OH
2 H2O, O2 and He
3 H2O, H2 and He

Answer:

22) B

When an atom decays by ß decay, its mass number remains the same.

Tritium beta decays into Helium-3 (isotope of Helium which has a mass number 3). You may have figured it out already as all three options have He as a product.

It may seem that HTO will form HeOH as both are single molecules. However, He is a noble gas and does not react with or form molecules with other elements. Therefore, HeOH cannot be a product.

Tritium will form an He atom on its own.

Let us look at equations 2 and 3 and try to balance them. We can substitute He with T as we know T will form He.

4HTO -> 2H₂O + O₂ + 4T 

HTO -> H₂O + H₂ + T (not possible to balance)

If we try to balance both equations, you will realise that it is not possible to balance the second equation.

Hence only equation 2 is possible. B is the answer.