From the experiment , we learn and observe precipitation of the solution ,we concluded from graph that point a enough of Pb(No3)2 (volume is 12.00 mL) to react with K2CrO4.(volume is 12.00 mL) is 7 point of graph ,since the 7 point to 11 point we observe that graph down slightly ,It might not have enough time in the reaction of solution .So the 7 point to 11 point has precipitation of solution the less constant when comparing with graph of theory.