You fill a tank with gas at 30°c and 101.5 kpa and seal it. you decrease the temperature to 10°c but keep the volume constant. what happens to the pressure? (careful!

Assume that the gas that fills the tank is ideal for us to be able to use the ideal gas law. 
                                 PV = nRT
When V, n, and R are all constant, we can say that,
                               (T1)(P2) = (T2)(P1)
We convert temperature into kelvin (This is the portion where we have to be very careful not using the degrees Celsius).
                                (30 + 273)(P2) = (10 + 273)(101.5 kPa)
The value of P2 is 94.8 kPa.

Well to my expert knowledge and my exquisite calculations i think the the negative ion # 412 is the key to sucess

Answer is: the equilibrium  shifts toward the reactants, to the left side of chemical reaction.it is because lead(ii) nitrate dissociates in water: pb(no₃)₂ → pb²⁺(aq) + 2no₃⁻(aq).according to lechatelier's principle, the position of equilibrium moves to counteract thechange (more lead cations, common ion), the position of equilibrium will move so that the concentration ofproducts decrease and concentration of reactants of chemical reaction increase.read more on -