Does sodium hydroxide react with calcium sulphate?

Sorry, Andrew Musson, but wherever you got your information from, using google, it's incorrect. CaSO4 +2NaOH = Ca(OH)2 + Na2SO4. Free Energy: ΔG(20C) = -87.3kJ (negative, so the reaction runs). Change in Enthalpy: ΔH(20C) = -88.1kJ (negative, so the reaction is exothermal). There, now! read more

The reaction between sodium hydroxide and calcium sulphate will not occur because the solubility of compounds determines the possibility of reaction. CaSO4 is almost insoluble. read more

Historically, sodium hydroxide was produced by treating sodium carbonate with calcium hydroxide in a metathesis reaction. (Sodium hydroxide is soluble while calcium carbonate is not.) This process was called causticizing. read more