How water become hard ?

Hard water becomes free from "….." ions when passed through ion exchange resin containing RCOOH groups.

Assertion: When cement is mixed with water and left as such, it becomes hard mass. Reason: Setting of cement is exothermic process.

What do you understand by Hard and Soft water? How is hardness of water removed by washing?

Distinguish between : a. Hard water and soft water b. Temporary hardness and permanent hardness

The hardness of water is measured by

Ground water is hard in the region of

A white chemical compound becomes hard on mixing with proper quantity of water. It is also used in surgery to maintain joints in a fixed position. Name the chemcial compound.