Chemistry MCQs for NEET — Practice Questions with Answers

Fluorine is the most electronegative element in the periodic table. So, it has the greatest proton affinity to form stable compounds.

Cu (s) + 2Ag²⁺ (aq) $\to$Cu²⁺ (aq) + 2Ag (s)

                E$°$ = 0.46 V at 298 K

             RT ln K = nFE$°$

                 ln K = nFE$°$/RT = (2 x 0.46)/0.0591 

                    K = 4 x 10¹⁵

As we know that

$∆$H = $∆$E + P$∆$V

or $∆$H = $∆$E + $∆$nRT

where $∆$H $\to$ change in enthalpy of system (standard heat at constant pressure)

$∆$E $\to$ Change in internal energy of system (Standard heat at constant volume)

An $\to$ no. of gaseous moles of product - no. of gaseous moles of reactant

R $\to$ gas constant

T $\to$ absolute temperature

If $∆$n = 0 for reactions which is carried out in an open container, therefore $∆$H = $∆$E

So for reaction (1) $∆$n = 2 - 2 = 0

Hence, for reaction (1), $∆$H = $∆$E

For the reaction,

 CH₄ (g) + 2O₂(g) $\rightleftharpoons$ CO₂ (g) + 2H₂O (l) $∆$H_r = -170.8 kJ mol^-1

This equilibrium is an example of heterogeneous chemical equilibrium. Hence, for it

    K_c = [CO₂]/[CH₄][O₂]²                ....(i)

(Equilibrium constant on the basis of conc.)

Thus, in it concentration of CO₂ (g) and H₂O (l) are not equal at equilibrium. The equilibrium constant (K_p) = [CO₂]/[CH₄][O₂] is not correct expression. In addition of CH₄(g) or O₂ (g) at equilibrium, K_c will be decreased according to expression (i) but Kc remains constant at constant temperature for a reaction, so for maintaining the constant value of K_c, the concentration of CO₂ will increase in same order. Hence on an addition of CH₄ or O₂, equilibrium will cause to the right. This reaction is an example of an exothermic reaction.