What is the density of N₂ gas 227^oC and 5.00 atm. pressure? (R = 0.082 L atm K^$$-$$1 mol^$$-$$1)

When 5 litres of a gas mixture of methane and propane is perfectly combusted at 0^oC and 1 atmosphere, 16 litres of oxygen at the same temperature and pressure is consumed, The amount of heat released from this combustion in kJ ($$\Delta $$H_comb. (CH₄) = 890 kJ mol^$$-$$1, $$\Delta $$H_comb. (C₃H₈) = 2220 kJ mol^$$-$$1) is

Three thermochemical equations are given below
(i)  C_(graphite) + O_2(g) $$ \to $$ CO_2(g); $$\Delta $$_rH^o = x kJ mol^$$-$$1
(ii)  C_(graphite) + $${1 \over 2}$$O_2(g) $$ \to $$ CO_(g); $$\Delta $$_rH^o = y kJ mol^$$-$$1
(iii)  CO_(g) + $${1 \over 2}$$O_2(g) $$ \to $$ CO_2(g); $$\Delta $$_rH^o = z kJ mol^$$-$$1
Based on the above equations, find out which of the relationship given below is correct.

Accumulation of lactic acid (HC₃H₅O₃), a monobasic acid in tissues leads to pain and a feeling of fatigue. In a 0.10 M aqueous solution, lactic acid is 3.7% dissociates. The value of dissociation constant, K_a, for this acid will be