If the volume of wet gas collected over water is 85.0 ml at 20°c and 760 mm hg , what is the volume of dry gas at stp conditions? (the vapor pressure of water at 20°c is 17.5 mm hg.) express your answer with the appropriate units.

77.4 mL

Explanation:

Combined gas law is the combination of Boyle's law, Charles's law and Gay-Lussac's law.

The combined gas equation is:

where,

= initial pressure of dry gas = (760 - 17.5) mmHg= 742.5 mm Hg

= final pressure of dry gas at STP =  760 mm Hg

= initial volume of dry gas = 85.0 mL

= final volume of dry gas at STP = ?

= initial temperature of dry gas =

= final temperature of dry gas at STP =

Now put all the given values in the above equation, we get the final volume of wet gas at STP

Volume of dry gas at STP is 77.4 mL.