Q. Which of the following pairs of ions make the water hard?
A) ${NH}_{4}^{+},\ {Cl}^{-}$
B) ${Ca}^{+},\ {HCO}_{3}^{-}$
C) ${Ca}^{2 +},\ {NO}_{3}^{-}$
D) ${Na}^{+},\ {SO}_{4}^{2 -}$
Explanation
The correct answer is Option B: ${Ca}^{+},\ {HCO}_{3}^{-}$.
A detailed explanation for this question is being prepared.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.