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 answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this