Answer : The volume of dry oxygen gas at STP is, ![58.8cm^3](https://tex.z-dn.net/?f=58.8cm%5E3)
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,
![\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}](https://tex.z-dn.net/?f=%5Cfrac%7BP_1V_1%7D%7BT_1%7D%3D%5Cfrac%7BP_2V_2%7D%7BT_2%7D)
where,
= initial pressure of gas = 765 mmHg
= final pressure of gas = 760 mmHg (atSTP)
= initial volume of gas = ![68.0cm^3](https://tex.z-dn.net/?f=68.0cm%5E3)
= final volume of gas = ?
= initial temperature of gas = ![45^oC=273+45=318K](https://tex.z-dn.net/?f=45%5EoC%3D273%2B45%3D318K)
= final temperature of gas =
(at STP)
Now put all the given values in the above equation, we get:
![\frac{765mmHg\times 68.0cm^3}{318K}=\frac{760mmHg\times V_2}{273K}](https://tex.z-dn.net/?f=%5Cfrac%7B765mmHg%5Ctimes%2068.0cm%5E3%7D%7B318K%7D%3D%5Cfrac%7B760mmHg%5Ctimes%20V_2%7D%7B273K%7D)
![V_2=58.8cm^3](https://tex.z-dn.net/?f=V_2%3D58.8cm%5E3)
Therefore, the volume of dry oxygen gas at STP is, ![58.8cm^3](https://tex.z-dn.net/?f=58.8cm%5E3)