What the titration investigation has to do

The shape of the investigation

• The work runs over several weeks: you plan, run preliminary trials, modify, run the real titrations, calculate, and write it up.
• Every part of the write-up does a specific job. Knowing all of them before you start is worth more than any amount of extra data.

What a strong investigation contains

• A plan built on evidence. You decide whether the sample or the procedure needs modifying, and the decision is made from preliminary trial results, not guessed in advance.
• Data good enough to conclude from. Enough titrations, recorded and processed, that the concentration is fixed by the data rather than by one lucky reading.
• Two concentrations determined, not one. The concentration of the standard solution and the concentration of the substance in the product. Assuming the standard solution's concentration from the bottle label is the commonest single omission in the whole investigation — every other number is measured against it.
• Control of variables explained, not just described. Say what each control did to the quality of the data, not only that you did it.
• A final answer with correct significant figures and units.
• A justified modification. Say what changing the sample or procedure did for validity and what it did for accuracy — they are different things.
• An evaluation that returns to the product. What does your number mean for the vinegar, the antacid, the bleach? A concentration with no interpretation is an unfinished investigation.

The four titration types

Four kinds of titration cover the contexts you will meet:

Type	What reacts	Typical context
Acid–base	H+ + OH−	vinegar, household ammonia, antacid tablets
Oxidation–reduction	electron transfer	vitamin C, bleach, iron tablets
Precipitation	ions forming an insoluble solid	chloride in soy sauce or saline
Complexometric	a ligand binding a metal ion	calcium or magnesium in hard water or milk

• Your teacher will normally set the context. What you choose within it — the modification, the concentrations, the indicator — is yours.

The two relationships you must use

Both appear in every titration calculation, and each does a different job:

$$n = \frac{m}{M} \qquad c = \frac{n}{V}$$

• $n$ — amount of substance, in mol

• $m$ — mass, in g

• $M$ — molar mass, in g mol⁻¹

• $c$ — concentration, in mol L⁻¹

• $V$ — volume, in L

• The first turns a weighed mass of solid into moles, which is how the standard solution is made up; the second turns titre volumes into moles. A titration that never uses one of them has skipped a step of the chemistry.

Choose a reaction whose mole ratio is not 1 : 1

• Aim for at least one calculation where the mole ratio actually does work — a ratio that is not 1 : 1.
• This is why contexts like sulfuric acid (2 : 1 with hydroxide), calcium carbonate antacids (1 : 2 with acid), or permanganate titrations (1 : 5 with iron(II)) are chosen so often.
• Titrate NaOH against HCl and the ratio is 1 : 1, so the moles of acid simply equal the moles of base and no stoichiometric reasoning is demonstrated at all. Write the balanced equation before you start and check what the ratio is.

What a finished report contains

• Purpose — which substance, in which product, and why it matters.
• Preliminary trials — what you tried, what happened, what you learned.
• Modification — what you changed, and why.
• Method — in enough detail to be repeated.
• Results — a table of titres, with the concordant ones identified.
• Processing — every calculation step shown.
• Conclusion — the concentration, with units and sensible significant figures.
• Evaluation — validity, accuracy, and what the answer means for the product.