When the weights of two elements combine with each other,their ratio is the ratio of their ......

Naturally occurring boron consists of two isotopes with atomic masses $10.01 \ (I)$ and $11.01 \ (II)$. The average atomic mass of natural boron is $10.81$. Find the percentage abundance of isotopes $(I)$ and $(II)$ respectively.

Chlorine has two isotopes $^{37}Cl$ and $^{35}Cl$ with percentage abundance of $25\%$ and $75\%$ respectively. Find the average atomic mass of chlorine.

The equivalent weight of which of the following is maximum? (Given: atomic weights $Na=23, Mn=55, Cr=52, K=39, O=16, C=12$)

$A$ metal oxide contains $32\%$ oxygen by mass. Its equivalent mass is:

Calculate the molar mass of naturally occurring argon from the data given in the following table:

Isotope	Molar Mass $(g \ mol^{-1})$	Abundance
$^{36}Ar$	$35.96755$	$0.337 \%$
$^{38}Ar$	$37.96272$	$0.063 \%$
$^{40}Ar$	$39.9624$	$99.600 \%$