Question

If calcium carbonate is put in distilled water will it
cause hardness. If not, why?​

Answer 1

Hello :)

No, it will not cause the hardness of the water.

Calcium carbonate only dissolves slightly in water, about 40ppm, but if you bubble carbon dioxide through the water you will slowly form calcium bicarbonate which is more soluble. If you can put the CO2 under pressure ( using a fizzy drink maker) the job will be quicker.

Without the use of CO2 you might get about 40ppm hardness with CO2 you will achieve a higher level of hardness.