State Henry's law.

Explanation

Henry's law: It states that ''the partial pressure of a gas in vapour phase (p) is proportional to the mole fraction of the gas `(chi)` in the solution '' and is expressed as p=`K_(H)chi`
where `K_(H)` is Henry's law constant.
Significance of `K_(H): As `p_(A)` = `K_(H)chi_(A)`. Thus, at constant temperature for the same partial pressure of different gases. `chi_(A) prop 1/K_(H)`. In other words solubility is inversely proportional to Henry's constant of the gas. Higher the value of `K_(H)`, lower is the solubility of the gas. As `H_(2)` is more soluble than helium,`H_(2)` will have lower value of`K_(H)` than that of helium.