Write the observations for the following:
(i) Reaction between HCl(g) and NH₃ (g)
(ii) Piece of magnesium ribbon is placed over flame
(iii) Zinc oxide is heated in a test tube
(iv) Dilute sulphuric acid is added to Zinc sulphide
(v) Heating the crystals of pure sodium chloride
Answers
Observations of above reactions are as follow:--
(i) Reaction of HCl(g) with NH3(g) is we get ammonium chloride. We know that ammonia is weak base and when it reacts with hydrochloric acid we get ionic compound ammonium chloride.
HCl(g) + NH3(g)------>NH4Cl
(ii)When piece of magnesium ribbon is placed over a flame it burns with bright white light. It is exothermic reaction as a large amount oh heat is also produced. Magnesium burns in present of oxygen so we get white ash of magnesium oxide. Reaction is;--
Mg + O2------>MgO(s)
(iii)When zinc oxide is heated it changes it colour. Zinc oxide crystal is white in colour, on heating it does not decompose rather changes its colour to yellow. On further heating the compound is directly converted to gas from white solid that is ZnO sublime ithout decomposition.
(iv)When dilute sulphuric acid is added to zinc sulphide we get zinc sulphate, sulphur dioxide and water vapours. The reaction is endothermic as the reaction takes place at high temprerature. Reaction is:--
ZnS + 4H2SO4-------->ZnSO4 + 4SO2 + 4H2O
(v)On heating the crystals of pure sodium chloride we get ionic or molten state of sodium and chloride that is we get sodium metal ions and chloride ions the chloride ions together form chlorine gas which is chocking in nature. Reaction is:--
NaCl(s) + heat--------->Na^+1 + Cl^-1------->Na^+1 + Cl2(g)