a colourless odourless gas A reacts with magnesium to form a white solid B. B on hydrolysis gives a pungent smelling gas C .Whaen a glass rod dipped in conc Hcl is brought near to C, a white cloud D is formed. What are A,B,C and D.Write the balanced chemical equations

(a) If on treatment with warm conc. H2 SO4 the salt gives a colourless gas with pungent smell or and if the gas which gives dense white fumes with ammonia solution, then the salt may contain Cl– ions and the following reaction occurs. NaCl + H2SO4 ⎯→ NaHSO4 + HCl Sodium Hydrogen chloride hydrogen sulphate Colourless gas HCl + NH3 ⎯→ NH4 Cl Ammonium chloride White fumes (b) If a salt gives effervescence on heating with conc. H2SO4 and MnO2 and a light greenish yellow pungent gas is evolved, this indicates the presence of Cl– ions. MnO2 + 2NaCl + 2H2SO4 ⎯→ Na2SO4 + MnSO4 + 2H2O + Cl2 (c) Salt solution acidified with dilute HNO3 on addition of silver nitrate solution gives a curdy white precipitate soluble in ammonium hydroxide solution. This indicates the presence of Cl– ions in the salt. NaCl + AgNO3 ⎯→ NaNO3 + Ag Cl Silver chloride (White precipitate) AgCl + 2NH4 OH ⎯→ [Ag(NH3) 2 ]Cl + 2H2 O Diammine silver (I) chloride