Question

What will be the change in the mass (in grams) of $1\, mol$ benzene if all hydrogen atoms are replaced by tritium atoms?
[Atomic masses: Hydrogen $=1\, u$, Tritium $=3 \,u$, Carbon $=12\, u$ ]

Answer 1

Mass of $1 \,mol$ of benzene $\left( C _{6} H _{6}\right)=78 \,g$
If all hydrogen atoms are replaced by tritium atoms, then formula becomes $C _{6} T _{6}$.
Mass of $1 \,mol$ of $C_{6} T_{6}=90\, g$
Difference $=90-78=12 \,g$