Why sodium sulphate has water absorbing capability?

At first I thought maybe sodium sulphate in contact with water produces sulphuric acid which absorbs water but I do not think it is actually a valid reason. 




Sodium sulphate reacts readily with water at room temperature to form hydrates up to sodium sulphate decahydrate, $\ce{NaSO4\cdot10H2O}$. $$\ce{NaSO4 + 10H2O -> NaSO4\cdot10H2O}$$ This means that $\ce{NaSO4}$ can absorb up to 10 mol of water for every 1 mol of salt that is used, making it one of the most effective drying agents in terms of sheer capacity.


Using data from this [source](http://www.chem.ucla.edu/~bacher/Specialtopics/Drying%20Agents.html) we can calculate the Gibbs energy change for the above reaction at different temperatures. $$\mathrm{\Delta G\_{20^\circ C} = -1.33~kJ~mol^{-1}}$$ $$\mathrm{\Delta G\_{30^\circ C} = 1.28~kJ~mol^{-1}}$$ 


Since the entropy change for the reaction is negative, we can see that the cooler the solution you are trying to dry is, the more effective $\ce{NaSO4}$ will be as a drying agent.


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