If I crush a tablet containing 1000 mg of CaCO3 in 25 ml of H2O, and the add 25 ml of 0.1N HCl, what will pH be?

This is part of a science fair project on antacids. I actually have 3 questions that need answering. I first had to measure the pH of the 1000 mg of CaCO3 in H2O both experimentally and theoretically. The theoretical pH I calculated was 9.96 ( not sure!) and the experimental pH was about 9. I then proceeded to add the 25 ml of 0.1 N HCl and the resultant experimental pH ranged from 7.5 to 8.5 with 2 random values out of 20 below 7. I was unable to calculate the theoretical pH probably because it involves using multiple Ka and Kb values. Finally, I tried crushing the 1000 mg CaCO3 tablet and then added 25 ml of 0.1N HCl to see if the experimental values were different, however the results were quite similar. So basically I need A) the theoretical pH of 1000mg of CaCO3 in 25 ml of H2O.B) the theoretical pH after the addition of 25 ml of 0.1 N HCl. C) the theoretical pH if the tablet of 1000 mg of CaCO3 was crushed and then 25 ml of 0.1N HCl was directly added