Which of the following ions does not liberate hydrogen gas on reaction with dilute acids ?

A gas undergoes change from state A to state B. In this process, the heat absorbed and work done by the gas is 5 J and 8 J, respectively. Now gas is brought back to A by another process during which 3 J of heat is evolved. In this reverse process of B to A :

50 mL of 0.2 M ammonia solution is treated with 25 mL of 0.2 M HCl. If pK_b of ammonia solution is 4.75, the pH of the mixture will be :

To find the standard potential of M³⁺/M electrode,the following cell is constituted : Pt/M/M³⁺(0.001 mol L⁻¹ )/Ag⁺(0.01 mol L⁻¹ )/Ag

The emf of the cell is found to be 0.421 volt at 298 K. The standard potential of half reaction M3⁺ + 3e⁻$$ \to $$ M at 298 K will be :

(Given $$E_{A{g^ + }\,/\,Ag}^ - $$ at 298 K = 0.80 Volt)