Chemistry
What do you understand by the water of crystallisation?
Give four substances which contain water of crystallisation and write their common names.
Answer
It is the amount of water molecules which enter into loose chemical combination with the salts and can be driven out by heating the crystals above 100°C.
| Chemical name | Formula | Common name |
|---|---|---|
| Sodium carbonate decahydrate | Na2CO3.10H2O | Washing soda crystals |
| Magnesium sulphate heptahydrate | MgSO4.7H2O | Epsom salt |
| Sodium sulphate decahydrate | Na2SO4.10H2O | Glauber's salt |
| Copper (II) sulphate pentahydrate | CuSO4.5H2O | Blue vitriol |
Related Questions
Which of the following methods A, B, C, D or E is generally used for preparing the chlorides listed below from (i) to (v). Answer by writing down the chloride and the letter pertaining to the corresponding method. Each letter is to be used only once.
A Action of an acid on a metal B Action of an acid on an oxide or carbonate C Direct combination D Neutralization of an alkali by an acid E Precipitation (double decomposition) (i) Copper (II) chloride (ii) Iron (II) chloride (iii) Iron (III) chloride (iv) Lead (II) chloride (v) Sodium chloride Choose the most appropriate answer from
[SO2, SiO2, Al2O3, CO, MgO, Na2O]
(a) A covalent oxide of a metalloid
(b) An oxide which when dissolved in water form acid.
(c) A basic oxide
(d) An amphoteric oxide
(a) Define efflorescence. Give examples.
(b) Define deliquescence. Give examples.
Answer the questions below:
(a) What name is given to the water in the compound copper sulphate-5-water?
(b) If copper sulphate-5-water is heated, anhydrous copper sulphate is formed. What is it's colour?
(c) By what means, other than heating, could you dehydrate copper sulphate-5-water and obtain anhydrous copper sulphate?
(d) Name a deliquescent salt.
(e) Why does hydrated copper sulphate turn white on heating?