Question

Match the effects on the concentration of SO3 gas when the following changes occur after initial equilibrium has been established in this system (N.C. = no change). 2SO2(g) + O2(g) 2SO3(g) + 46.8 kcal pressure increases increase [O2] increase volume of chamber adding a catalyst raising the temperature

Answer 1

The reaction is

$2SO_{2} (g)+O_{2}(g)->2SO_{3} (g)+46.8 kcal$

1) the system is homogeneous with all the reactants and products are gases

2) there are three moles on reactant side and two moles on product side

i) If we increase pressure then there will be decrease in volume. It will cause increase in moles per unit volume. So if we increase pressure the equilibrium will shift towards side having less number of moles of gaseous species.

Thus system will move in forward direction.

ii) If we increase concentration of oxygen it means we are increasing concentration of reactants,this will cause system to shift in forward direction

iii) If we increase volume of chamber,  it will cause decrease in moles per unit volume, hence the system will move in the direction where number of moles of gaseous species is more, System will shift in reverse direction

iv) There is generally no effect of catalyst on equilibrium. However an increase in temperature will cause shift in reverse direction.

Answer 2

The effects on the concentration of SO3 gas when the following changes occur after initial equilibrium has been established in this system (N.C. = no change) by adding a catalyst.

2SO2(g) + O2(g)  2SO3(g) + 46.8 kcal

So that even though there is an addition of catalyst, no change in reactants or products has occurred because catalyst only provides a faster pathway for the reaction to occur.