Why removing all UO2 affects equilibrium but removing some doesn't

[lha08]

Homework Statement

Suppose the reaction system UO2(s) +4HF(g) <-> UF4(g) +2H2O(l)
is sealed in a container and allowed to equilibrate at a particular temperature.

Explain what happens to the nature of each substance if you:
a. remove some UO2 from the system
b. remove all UO2 from the system

Homework Equations

The Attempt at a Solution

I know that UO2 is solid and that it does not affect the equilibrium but in my answers it says that a) will have no effect while b) will increase [HF] and decrease [UF4]...why is that? I thought that all solids will have no effect no matter how much you take out..Thanks.

 

[Borek]

Soilds have no effect as long as they exist. If the soid doesn't exist, system will shift the equilibrium till the solid appears.