during an experience three test tubes are filled with distilled water tap water and hard distilled water
Answers
because the distilled water has no ions
When soap reacts with hard water, it forms an insoluble compound known as lime soap. Hard water has calcium and magnesium ions in it. These ions displace the sodium component of soap, reacting with the fatty acid part of soap form the insoluble compound known as lime soap which are dirty, white and curd like substances seen floating on the water.
The reaction for the calcium ions and the fatty acids in soap, is as follows:
2 C₁₇H₃₅COO⁻Na⁺ + Ca2⁺ --------------> (C₁₇H₃₅COO)2Ca + 2 Na⁺
This is why it is so difficult to form lather in hard water, the calcium and magnesium ions react with the fatty acids, instead to form these insoluble lime soaps.
In this case, the hard water is the water in test tube C which is hand pump water which is from a borehole. Hand-pumped borehole water are usually hard water. This water will for the lime soaps in the test tube
Distilled water and tap water are soft water, usually lathering quite easily and do not form the white, dirty, curd like lime soaps. Therefore these lime soaps will not be found in test tube A or B.