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Describe an experiment, with labelled diagram to investigate whether calcium sulfate is insoluble or soluble in water at room temperature.

Explanation:

Soluble anhydrite β-CaSO4 reacts with water vapour at room temperature to form CaSO4- 0.5H2O at 20-30% RH and CaSO4-0.6H2O at 70-80% RH. ... If a minute amount of a deliquescent salt (NaCl) is added to the initial sample, the same phenomenon is observed when relative humidity reaches the deliquescent point of the salt.

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.