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Q.
Which of the following alkaline earth metal sulphates is least soluble in water?
Haryana PMTHaryana PMT 2010
Solution:
The solubility of the alkaline earth metal sulphates in Water decreases down the group, because of the decrease in hydration energy due to increase in atomic size ie, $ Be > Mg >> Ca > Sr > Ba $ .
Remember, in case of sulphates of alkaline earth metals lattice energy remains almost constant as the size of metal increases, thus solubility is decided only by hydration energy.
Hence, $ BaSO_{4} $ is least soluble in water.