Question

What is meant by aqueous tension? How is the pressure exerted by a gas corrected to account for aqueous tension?

Answer 1

Hint: As we can see, Aqueous tension has the term ‘aqueous’ in it, which means “containing water”. Therefore, this question can be attempted by taking into account the relation between atmospheric pressure and pressure of moist air.

Complete step-by-step solution:

Aqueous tension is defined as, “the partial pressure of the water vapour that is present in the moist gas”.

The pressure exerted by moist gas is equal to the sum of partial pressure of dry vapour and moist vapour. This partial pressure exerted by water vapours is known as aqueous tension.

We can also put it in this way - aqueous tension is equal to the pressure exerted by saturated water vapour.

Gas present over the surface of any liquid becomes moist due to the presence of a water vapour, which is because of the phenomenon of evaporation.

Pressure exerted by a gas corrected to account for aqueous tension can be calculated by applying ‘Dalton’s Law of Partial Pressure’.

 $ \Rightarrow  $  $ {{P}_{total}}={{P}_{dry}}+{{P}_{\text{water vapour}}} $ 

Where,  $ {{P}_{water vapour}} $  = aqueous tension

 $ \Rightarrow  $   $ {{P}_{total}}-{{P}_{\text{water vapour}}}={{P}_{dry}} $ 

From the above equation, we can conclude that pressure exerted by a gas is corrected by using Dalton's law of partial pressure.

Note: Dalton’s Law of Partial Pressure is defined as - “At constant temperature, the pressure exerted by a mixture of two or more non-reacting gases enclosed in a definite volume, is equal to the sum of the individual pressures exerted by each gas if it was present alone in the same volume”.