You have a little beaker with an unknown amount of acid indicator solution in it. Over this beaker, you have a tube marked in ml. increments. This tube is marked backwards, it starts at 0 at the top and goes to 25 at the bottom. This tube contains 25ml. of hydrocloric acid (.01 concentration), which will drip out one drop at a time into the beaker. The acid indicator will eventually turn magenta and you will then close off the tube.

On one such test you recorded that you started out with 10.2ml in the tube. You used it down to the 24.8ml area. At which time you refilled the tube to 12.1ml. You shut off the tube at 13.1ml, when the acid indicator was a nice shade of magenta.

Now, please give me the equation for how much acid indicator was in the beaker in mols, and use it to actually find how much was in it, also in mols. For bonus points, tell me how this equation would be helpful in certain forensic investigations.

You wouldn't think a 13 yr. old would want to put you through such a hard time of it, would you? ^_^