If 68.0 cm 3 of oxygen gas is collected over water at 45 â°c and 765 mm hg, what is the volume of dry oxygen gas at stp? the vapor pressure of water at 45 â°c is 71.9mm hg.

Answer : The volume of dry oxygen gas at STP is,

Explanation :

First we have to calculate the pressure of oxygen gas.

Pressure of oxygen gas = Total pressure - Pressure of water

Pressure of oxygen gas = 765 mmHg - 71.9 mmHg

Pressure of oxygen gas = 693.07 mmHg

Now we have yo calculate the volume of dry oxygen gas at STP.

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 gas = 765 mmHg

= final pressure of gas = 760 mmHg  (atSTP)

= initial volume of gas =

= final volume of gas = ?

= initial temperature of gas =

= final temperature of gas =   (at STP)

Now put all the given values in the above equation, we get:

Therefore, the volume of dry oxygen gas at STP is,

the gas collects in coils that then becomes a liquid that then flows through the coils inside the refrigerator