Doctors use a paste of white substance in water to maintain a fractured bone fixed in its place. Identify this substance and write its chemical formula.

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

The blue colour of crystals of a substance changed on heating in a closed test tube but the colour was regained after some time on cooling. Name the substance and write its chemical formula. Explain the phenomenon involved.

A solution of substance 'X' is used for white washing. Name the substance 'X' and write its formula

The crystals of compound A on keeping in air get converted into a white powder. Its solution in water gives blue colour with red litmus. It is used to remove permanent hardness of water. Identify the substance. Write chemical formula of its crystalline form.

A water soluble compound 'X' of sodium on reacting with dil. H_2SO_4 released a colourless gas accompanied by brisk effervescence. When the gas was passed through water, the solution obtained turned blue litmus solution red. On bubling the gas through lime water, it initially became milky and the milkness disappeared when the gas was passed in excess. Identify the substance 'X' and write the chemical equation for the reactions involved.

A silver articles generally turns black when kept in the open for a few days. Name the black substance formed and give its chemical formula.

A substance X, which is an oxide of a group 2 element, is used intensively in the cement industry. This element is presented in bones also. On treatment with water it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.

Name the compound of calcium used for disinfecting drinking water. Give its chemical formula.