Question

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Answer 1

Answer:

presence of sodium carbonate causes hardness of water

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Answer 2

Answer:

5. option c : Ethane

6. option b : Magnesium sulphate

Explanation:

5. Addition reaction happens only with unsaturated compounds. Here except Ethane , other compounds are unsaturated compounds ( compounds with double/triple bond ) . So Ethane , as it is not unsaturated  => it will not undergo addition reaction.

6. Hardness of water is caused by magnesium/calcium salts.

Here , we have Magnesium sulphate which a magnesium salt => it will cause hardness of water.