Question

Equal weights of $HF$, $HCl$ ,$HBr$ , and $HI$ ${at87}^{0}C$ and $750mm$ $Hg$ pressure are taken. The correct sequence of these gases in the increasing order of their volume is ?

• A. HI<HBr<HCl<HF
• B. HBr<HI<HCl<HF
• C. HF<HBr<HCl<HI
• D. HI<HBr<HF<HCl

Answer 1

The correct option is A HI<HBr<HCl<HF

At given temperature and pressure, volume of a gas depends on its number of moles. So volume of a gas is directly proportional to the number moles of gas i.e. mass of the gas divided by molecular mass of that gas. Since all gases have equal weights, the gas having minimum molecular weight will have maximum volume. Now here increasing order of molecular weight is :

HF<HCl<HBr<HI

therefore increasing order of their volume will be : HI<HBr<HCl<HF