Question

`100 mL` sample of distilled water, tap water and boiled water required, respectively, `2 mL,17 mL` and `7 mL` of soap solution to form permanent lather. The ratio of permanent to temprorary hardness in the tap water is
A. `3:2`
B. `2:3`
C. `1:2`
D. `2:1`

Answer 1

Correct Answer - C
(c)
(Temprorary and permanent hardness) in tap `H_(2)O=15 mL`
Permanent in boiled `H_(2)O=5mL`
Temprorary hardness in `H_(2)O=15-5=10 mL`
`("Permanent hardness")/("Temporary hardness")=5/10=1:2`