Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
2.7k views
in Chemistry by (64.7k points)

What different methods are used for softening the hard water? Explain the principle used in each method? (Write any two)

1 Answer

+1 vote
by (62.3k points)
selected by
 
Best answer

Hard water can be softened by the following methods depending upon the nature of hardness. 

(a) Temporary hardness : 

1. By boiling. It can be removed by merely boiling the water. Boiling decomposes the bicarbonates to give carbon dioxide and insoluble carbonates, which can be removed by filtration.

2. Clark’s process : Temporary hardness can be removed, by the addition of a calculated amount of lime, where magnesium carbonate or calcium carbonate is precipitated. 

Ca(HCO3)2 + Ca(OH)2 → 2CaCO3 + 2H2

Mg(HCO3)2 + Ca(OH)2 → CaCO3 + MgCO3 + 2H2

(b) Permanent hardness: With sodium carbonate. On treatment with washing soda, Ca2+ and Mg2+ in hard water are precipitated. The precipitate of the insoluble carbonates thus formed is removed by filtration.

The anion may remain in solution but in this form it is not dangerous.

(ii) Ion-exchange method. The common substances used for this process is zeolite which is hydrated sodium aluminium silicate, NaAl(SiO2)2. The exchange occurs when on passing over the zeolite bed, sodium ions from zeolite are replaced by calcium and magnesium ions.

Thus . 

2NaZe + Ca2+ → (Ze)2Ca + 2Na+ ;

2NaZe + Mg2+ → (Ze)2Mg + 2Na+

When all the sodium ions of zeolite has been replace, the zeolite is said to be exhausted. It can be regenerated by treatment with strong solution of sodium chloride. 

2Na + (Ze)2 Ca → 2ZeNa + Ca2+

Related questions

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...