How to Calculate Concentration Titration
- 1). Put on chemical splash goggles, coat and gloves, then relocate your equipment to the fume hood (if it isn't under the fume hood already). Make sure all equipment is in good working order and that glassware doesn't have any cracks or defects.
- 2). Determine whether the solution you want to test is an acid or a base (you should already know this before beginning the experiment). If it's an acid, fill the burette with .1 molar sodium hydroxide. If it's a base, fill the burette with .1 molar hydrochloric acid.
- 3). Place the pH meter probe in the solution in the Erlenmeyer flask, being sure to follow any applicable manufacturer's instructions when you do so. Place the Erlenmeyer flask beneath the burette.
- 4). Add a few drops at a time of the sodium hydroxide/hydrochloric acid to the solution in the Erlenmeyer flask and record the pH after every few drops, together with the volume of .1 molar sodium hydroxide/hydrochloric acid you've added so far. The pH should change slowly at first, then suddenly rise or fall rapidly and finally stabilize again. Once it stabilizes again, cease adding acid/base.
- 5). Graph the data you've collected on your paper. The curve on the graph will be more or less s-shaped, The point where the line on the graph rises rapidly is where the pH is changing most swiftly. Find the volume of sodium hydroxide/hydrochloric acid you had to add to reach this point on the graph and write it down.
- 6). Write out the chemical equation for the acid/base neutralization reaction that took place. If you added sodium hydroxide to acetic acid, for example, the equation would be CH3COOH (aq) + NaOH (aq) --> NaCH3COO (aq) + H2O (l). Note the ratio between the reactants. In this case, for example, the ratio between the reactants is one-to-one, but that will not be true for all reactions.
- 7). Multiply the volume of sodium hydroxide/hydrochloric acid you added by .1 to obtain the number of moles you added. If you added 1 liter of sodium hydroxide/hydrochloric acid, for example, that means you added .1 moles, since the chemical had .1 molarity. Now multiply the number of moles by the ratio between the reactants from step 6 above. If you added .1 moles of sodium hydroxide to an acetic acid solution, for example, since the ratio is one-to-one there were .1 moles of acetic acid in the original solution.
- 8). Divide the number of moles of solute in the original solution by the volume of the original solution to find its concentration.
