When hard water is evaporated completely, the white solid remains in the container. It may be due to the presence of 1. Carbonates of Ca and Mg 2. Sulphates of Ca and Mg 3. Chlorides of Ca and Mg Select the correct answer using the code given below :

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Q: 7 (CDS-I/2015)
When hard water is evaporated completely, the white solid remains in the container. It may be due to the presence of
1. Carbonates of Ca and Mg
2. Sulphates of Ca and Mg
3. Chlorides of Ca and Mg
Select the correct answer using the code given below :

question_subject: 

Science

question_exam: 

CDS-I

stats: 

0,13,37,25,13,7,5

keywords: 

{'hard water': [0, 0, 0, 2], 'carbonates': [0, 0, 1, 3], 'chlorides': [0, 0, 2, 2], 'sulphates': [0, 0, 1, 3], 'container': [1, 0, 2, 2]}

When hard water is evaporated, the process of evaporation removes the water, leaving behind the dissolved minerals that were present in the water. The white solid residue that remains in the container after evaporation is mainly caused by the presence of carbonates of calcium (Ca) and magnesium (Mg).

Option 1: Carbonates of Ca and Mg - This option correctly identifies one of the main causes for the white solid residue. When hard water contains high levels of dissolved carbonates, these compounds can precipitate out as solid white residues when the water evaporates.

Option 2: Sulphates of Ca and Mg - This option is incorrect. While hard water can contain dissolved sulphates of calcium and magnesium, these compounds do not typically form white solid residues upon evaporation.

Option 3: Chlorides of Ca and Mg - This option is incorrect. Chlorides of calcium and magnesium do not contribute to the formation of white solid residues during the evaporation process.

Based on the explanation above, the correct answer is option 2: 1, 2 and 3.

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