Which one of the following has an optical isomer ?
(en = ethylenediamine)

29.5 mg of an organic compound containing nitrogen was digested according to Kjeldahl’s method and the evolved ammonia was absorbed in 20 mL of 0.1 M HCl solution. The excess of the acid required 15 mL of 0.1 M NaOH solution for complete neutralization. The percentage of nitrogen in the compound is

The time for half life period of a certain reaction A $$\to$$ products is 1 hour. When the initial concentration of the reactant ‘A’, is 2.0 mol L^–1, how much time does it take for its concentration to come from 0.50 to 0.25 mol L^–1 if it is a zero order reaction ?

Consider the reaction :

Cl₂(aq) + H₂S(aq) → S(s) + 2H⁺ (aq) + 2Cl^– (aq)

The rate equation for this reaction is rate = k [Cl₂] [H₂S]

Which of these mechanisms is/are consistent with this rate equation?

(A) Cl₂ + H₂S $$\to$$ H⁺ + Cl^– + Cl⁺ + HS^– (slow)

Cl⁺ + HS^– $$\to$$ H⁺ + Cl^– + S (fast)

(B) H₂S $$ \Leftrightarrow $$ H⁺ + HS^– (fast equilibrium)

Cl₂ + HS^– $$\to$$ 2Cl^– + H⁺ + S (slow)