One day Kamal saw that her mother was roasting peanuts in a pan (kadahi) in the kitchen and she had taken ordinary salt
One day Kamal saw that her mother was roasting peanuts in a pan (kadahi) in the kitchen and she had taken ordinary salt to roast the peanuts. She was surprised to observe that in spite of very high temperature, the salt does not melt and the peanuts also get roasted.
1. The chemical name of common salt is :
(a) Potassium chloride
(b) Sodium carbonate
(c) Sodium hydrogen carbonate
(d) Sodium chloride
2. Common salt is :
(a) A covalent compound
(b) An ionic compound formed by sharing electrons
(c) An ionic compound formed by the transfer of electrons
(d) Soluble in organic solvents
3. Common salt is not a raw material for :
(a) Bleaching powder
(b) Plaster of Paris
(c) Baking soda
(d) Caustic soda
4. Common salt is used as a raw material in the preparation of washing soda in which the number of molecules of water of crystallisation is :
(a) 10
(b) 7
(c) 5
(d) 2
1 Answers
1. (d) sodium chloride
sodium chloride (NaCl)
2. (c) An ionic compound formed by the transfer of electrons
common salt is an ionic compound formed by the transfer of electrons
Na \(\longrightarrow\) Na+ + e-
1/2 Cl2 + e- \(\longrightarrow\) Cl-
Na+ + Cl- \(\longrightarrow\) NaCl (Common salt)
3. (b) Plaster of paris
When electricity is passed through an aqurous solution of common salt (brine NaCl(aq)), chlorine gas given off and sodium Hydroxide (Castic soda) is formed.
2 NaCl (aq) + 2H2O(l) \(\overset{\text{elecrolysis}}{\longrightarrow}\) \(\underset{\text{Caustic soda}}{2NaOH} + Cl_2\)↑ + H2↑
When chlorine which is evolved during electrolysis of NaCl passed through Ca(OH)2 solution, bleaching powder is formed
Ca(OH)2 + Cl2 \(\longrightarrow\) \(\underset{\text{bleaching powder}}{CaOCl_2}\) + H2O
CO2 + H2O + NH3 + NaCl \(\longrightarrow\) \(\underset{\text{Baking soda}}{NaHCO_3} + NH_4Cl\)
Plaster of paris is prepared by heating calcium sulphate dihydrate
2 CaSO4 . 2H2O \(\overset{\triangle}{\longrightarrow}\) \(\underset{\text{plaster of paris}}{2CaSO_4}\).H2O
Hence, NaCl (common salt) is not used as a raw material in plaster of paris.
4. (a) 10
Na2CO3 . 10H2O