If water contains calcium hydrogen carbonate, out of soap and synthetic detergents which one will you use for cleansing clother ?

Explanation

If water contains calcium hydrogen carbonate, `Ca(HCO_3)_2` which is quite soluble in water, the water becomes hard due to the presence of `Ca^(2+)` ions.
`Ca(HCO_3)_2 (aq) iff Ca^(2+)(aq) + 2HCO_3^(-) (aq)`
When soap (say sodium sterate) is added to such a water, a lot of soap is wasted as it is into insoluble calcium soap.
`underset("Sod. stearate (Soap)")(2C_(17) H_(35) COO^(-) Na^(+)) + Ca^(2+) to underset("Cal. stearate (Insoluble)")((C_(17)H_(35) COO)_2 CA darr + 2Na^(+))`
On the other hand, `Ca^(2+)` salts of sulphonic acids present in commom detergents are quite soluble in water and as such water containing `Ca(HCO_3)_2` will lather freely with synthetic detergents. Thus, if water contains `Ca(HCO_3)_2`, then will use synthetic detergents for cleasing clothes.