Acids, Bases - 16 PDF

What does 10H2O signify? Does it make Na2CO3 wet? We will address this question in the next section. Sodium carbonate and sodium hydrogencarbonate are useful chemicals for many industrial processes as well. Uses...

What does 10H2O signify? Does it make Na2CO3 wet? We will address this question in the next section. Sodium carbonate and sodium hydrogencarbonate are useful chemicals for many industrial processes as well. Uses of washing soda (i) Sodium carbonate (washing soda) is used in glass, soap and paper industries. (ii) It is used in the manufacture of sodium compounds such as borax. (iii) Sodium carbonate can be used as a cleaning agent for domestic purposes. (iv) It is used for removing permanent hardness of water. 2.4.4 Are the Crystals of Salts really Dry? Activity 2.15 n Heat a few crystals of copper sulphate in a dry boiling tube. n What is the colour of the copper sulphate after heating? n Do you notice water droplets in the boiling tube? Where have these come from? n Add 2-3 drops of water on the sample of copper sulphate obtained after heating. n What do you observe? Is the blue colour of copper sulphate restored? Figure 2.9 Copper sulphate crystals which seem to be dry contain water of Removing water crystallisation. When we heat the crystals, this water is removed and the of crystallisation salt turns white. If you moisten the crystals again with water, you will find that blue colour of the crystals reappears. Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt. Five water molecules are present in one formula unit of copper sulphate. Chemical formula for hydrated copper sulphate is Cu SO4. 5H2O. Now you would be able to answer the question whether the molecule of Na2CO3.10H2O is wet. One other salt, which possesses water of crystallisation is gypsum. It has two water molecules as water of cyrstallisation. It has the chemical formula CaSO4.2H2O. Let us look into the use of this salt. Plaster of Paris On heating gypsum at 373 K, it loses water molecules and becomes 1 calcium sulphate hemihydrate ( CaSO 4. H O ). This is called Plaster of 2 2 32 Science 2024-25