6 ml of a standard soap solution (1ml = 0.001g of `CaCO_3` ) were required in titrating 50ml of water to produce a good lather. Calculate the degree of hardness.

Explanation

50 ml of hard water sample requires 6 ml of soap solution.
Volume of soap solution required for `10^6` ml of hard water to get good lather ` = (10^6 xx 6)/(50)= 0.12 xx 10^6 ml`
Given that if 1ml soap is required for the water sample to get good lather that sample contains 0.001g of `CaCO_3`
1ml soap `to 10^3 g CaCO_3`
`0.12 xx 10^6` ml soap `to`
Weight equivalent of `CaCO_3` = 120 g
Degree of hardness of water sample = 120ppm