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 ?

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

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

A solution containing 2.675g of CoCl₃. 6NH₃ (molar mass = 267.5 g mol^–1) is passed through a cation exchanger. The chloride ions obtained in solution were treated with excess of AgNO₃ to give 4.78 g of AgCl (molar mass = 143.5 g mol^–1). The formula of the complex is : (At. Mass of Ag = 108 u)