Question

​In a titration of 100 ml of water, 12 ml of saturated soap solution were required to produce good lather.What will be the degree of hardness of the sample?[1ml=0.001g of ${CaCO}_3$]

• A. 100 ppm
• B. 120 ppm
• C. 60 ppm
• D. 80 ppm

Answer 1

The correct option is B

120 ppm

100 ml of hard water sample reqiures 12ml of soap solution

Volume of soap solution required for ${10}^6$ ml of hard water to form lather= $\frac{{10}^{6}X12}{100}$ = 0.12 x ${10}^6$ ml

Given, 1 ml soap solution = 0.001 g =${10}^{-}$${}^3$) g of ${CaCO}_3$

∴ 0.12 x ${10}^6$ ml soap solution ?

Weight equivalent of ${CaCO}_3$ =120g

∴Degree of hardness of the water sample =120 ppm