Question

A `100 mL` of tap water was titrated with `M//50 HCl` with methyle orange as indicator. If `30 mL of HCl` were required. Calculate the hardness of `CaCO_(3)` per `10^(3)` parts of water. The hardness is temporary.
A. `150 "ppm"`
B. `600 "ppm"`
C. `275 "ppm"`
D. `300 "ppm"`

Answer 1

Correct Answer - D
Meq. of `CaCO_(3)`= Meq. of `Ca(HCO_(3))_(2)` = Meq. of HCl
`(W)/(100//2)xx 1000= (1)/(50) xx 30`
`W_(CaCO_(3))= (3 xx 100 )/(5 xx 2000) = 0.03 g`
`therefore 100 mL " of "H_(2)O " contins " Ca^(2+)= (0.03 xx 10^(6))/(100)= 300 "ppm"`