To improve air quality and obtain a useful product, chemists often remove sulfur from coal and natural gas by treating the contaminant hydrogen sulfide with O2: 2H2S(g) + O2(g) = 2S(s) + 2H2O(g)

What happens to

a) [H2O] if O2 is added?

b) [H2S] if O2 is added?

c) [O2] if H2S is removed?

d) [H2S] if sulfur is added?

1) Increase

2) Decreases

3) increases

4) Increase

Explanation:

These questions can only be answered by considering the principle which states that, "When a constraint such as a change in concentration, pressure or volume is imposed on a reaction system in equilibrium. The system will readjust itself in order to annul the constraint."  

Now, if more reactants are added, the equilibrium position will shift towards the right, If more products are added, the equilibrium position will shift to the left.

Similarly, the removal of H2S causes the O2 concentration to increase since the equilibrium position now shifts to the left.

Also, addition of O2 causes H2S to be removed as the equilibrium moves to the right.

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.