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I'm not sure which of following two methods will give better yields for $\ce{CaSO4}$:

A. Add dilute $\ce{HNO3}$ to $\ce{CaCO3}$, followed by dilute $\ce{H2SO4}$; or

B. Titrate aqeuous calcium hydroxide with dilute sulfuric acid.

I'm leaning towards Method B since it is easier to point out when the reaction is complete, and the yield would thus be close to 100%.

For Method A, however, any excess $\ce{CaCO3}$ would react with $\ce{H2SO4}$ and any excess $\ce{Ca(NO3)2}$ might undergo a displacement reaction where $\ce{NO3-}$ ions are displaced by $\ce{SO4^2-}$.

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  • $\begingroup$ A if yield is based on precipitation (compare calcium sulphate and hydroxide solubilities), B if on evaporation. $\endgroup$
    – Poutnik
    Jun 6 at 17:05
  • $\begingroup$ Consider that in A. you add an extra species that is not needed in the end, and in B., the only product besides gypsum is water. $\endgroup$ Jun 6 at 20:12
  • $\begingroup$ Are you going to evaporate the leftover solution? $\endgroup$ Jun 11 at 13:58

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