(i) In a pregnant women, the oxygen supply for the fetus is provided by the maternal blood in the placenta where the blood vessels of both mother and fetus are in close proximity. Both fetal and maternal hemoglobin binds to oxygen reversibly as follows.
Hb_(mother) + O₂ ⇌ HbO_{2 (mother)}
Hb_(fetus) +O₂ ⇌ HbO₂ (fetus)
(ii) In the above two equilibrium, the equilibrium constant value for the oxygenation of fetal hemoglobin is higher which is due to its higher affinity for oxygen compared to adult hemoglobin. Hence in placenta, the oxygen from the mother's blood is effectively transferred to fetal hemoglobin.

In this equilibrium N₂(g) + 3H₂Cg)⇌ 2NH₃(g) ΔH = - 92.2 kJ.
Forward reaction is exothermic while the reverse reaction is endothermic. If the temperature of the system increased, the system responds by decomposing some of ammonia molecules to nitrogen and hydrogen by absorbing the supplied heat energy.
Similarly, the system responds to a drop in the temperature by forming more ammonia molecule from nitrogen and hydrogen which release heat energy.

(i) When the total number of moles of gaseous reactants and gaseous products are equal, the change in pressure has no effect on system at equilibrium.
H₂(g) + I_z(g)⇌ 2HI(g)
Here the number of moles of reactants and products are equal. So the pressure has no effect on such equilibrium with Δn_g = O

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
In the above equilibrium, if the pressure is increased, the volume will decreases. The system responds to this effect by reducing the number of gas molecules. i.e., it favours the formation of ammonia.
If the pressure is reduced, the volume will increases. It favours the decomposition of ammonia.

At equilibrium, the concentration of the reactants and products does not change. The addition of more reactants or products to the reacting system at equilibrium causes an increase in their respective concentration.
According to Le-Chatelier's principle, the effect of increase in concentration of a substance is to shift the equilibrium in a direction that consumes the added substance. For example,
H₂(g) + I₂(g) ≓ 2HI(g)
The addition of H₂ or I₂ to the equilibrium mixture, disturbs the equilibrium. In order to minimize the stress, the system shifts the reaction in a direction where H₂ and I₂ are consumed i.e., formation of additional HI would balance the effect of added reactant. Hence the equilibrium shifts to the right (forward direction). i.e., the equilibrium is re-established. Similarly, removal of HI (Product) also favours forward reaction.
If HI is added to the equilibrium mixture, the concentration of HI is increased and system proceeds in the reverse direction to nullify the effect of increase in concentration of HI.