A certain amount of oxygen is prepared by thethermal decomposition of potassium chlorate and is collected by downward displacement of water. The pressure of the gascollected is measured with the help of a manometer. The pressure recorded is found to be more than thepressure recorded for the same volume of oxygen cylinder containing same amount of oxygen under the same conditions. How do you account for this deviation?

A certain amount of oxygen is prepared by thethermal decomposition of

1.	A certain amount of oxygen is prepared by thethermal decomposition of potassium chlorate and is collected by downward displacement of water. The pressure of the gascollected is measured with the help of a manometer. The pressure recorded is found to be more than thepressure recorded for the same volume of oxygen cylinder containing same amount of oxygen under the same conditions. How do you account for this deviation?
Answer» SOLUTION :When oxygen is prepared , it is collected over water. SINCE water is in equilibrium with water vapour, the oxygen gas collected is not dry oxygen gas and it is mixed with some AMOUNT of water vapour. The total pressure exerted by thismoist oxygen gas is thesum of the PARTIAL pressures of oxygen and water vapour. The pressure recorded for the samevolume of pure and dry oxygen gas is obviously less than previous case. The pressure of WATERVAPOUR in the collected gas is called aqueous tension.