Given that the abundances of isotopes $^{54}Fe$,$^{56}Fe$ and $^{57}Fe$ are $5 \%$,$90 \%$ and $5 \%$,respectively,the atomic mass of $Fe$ is

The weight of a molecule of the compound $C_{60}H_{122}$ is

Which one of the following properties of an element is not variable?

Calculate the mass of a single atom of hydrogen.

$A$ metal chloride contains $49.5\%$ chlorine. The specific heat of the metal is $0.064 \ cal \ g^{-1} \ ^\circ C^{-1}$. What is the exact atomic weight of the metal?

Chlorine exists in two isotopic forms $^{35}Cl$ and $^{37}Cl$. If the average atomic mass of chlorine is $35.5$,what is the percentage abundance of these isotopes respectively?