Titration and a defensible concentration
| English | 中文 | Pinyin |
|---|---|---|
| titre/ˈtɪtə/ | 滴定体积 | dī dìng tǐ jī |
| equivalence point/ɪˈkwɪvələns pɔɪnt/ | 化学计量点 | huà xué jì liàng diǎn |
What would explain this observation?
- Higher-tier focus: A burette reading is not the delivered volume. The titre 滴定体积 is the difference between final and initial readings, and both readings have uncertainty.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- A titration measures the amount of one solution needed to react with a known amount of another. The equation gives the mole ratio. An indicator endpoint approximates the equivalence point 化学计量点 when a suitable indicator is used.
- titre: The volume delivered from a burette to reach the stated end-point; equivalence point: The point of stoichiometric reaction completion.
Why rinse the pipette with the solution it will transfer?
Calculate the known amount first, apply the stoichiometric ratio, then divide by the unknown solution volume in cubic decimetres. Use concordant titres as required by the school method and report the accepted values.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Calculate the known amount first, apply the stoichiometric ratio, then divide by the unknown solution volume in cubic decimetres. Use concordant titres as required by the school method and report the accepted values.
- Rinse the burette with its solution and the pipette with the solution it transfers. Rinse the flask with distilled water. Add titrant slowly near the endpoint, swirl, and read the meniscus at eye level. Use a white tile and appropriate eye protection.
Which two habits make the investigation or model in this case more defensible?
Rinse the burette with its solution and the pipette with the solution it transfers. Rinse the flask with distilled water. Add titrant slowly near the endpoint, swirl, and read the meniscus at eye level. Use a white tile and appropriate eye protection.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: 25.0 cubic centimetres of acid reacts 1:1 with 20.0 cubic centimetres of 0.100 mol per cubic decimetre alkali. n = cV = 0.100×0.0200 = 0.00200 mol. Acid amount is 0.00200 mol. c = n/V = 0.00200/0.0250 = 0.0800 mol per cubic decimetre.
Burette readings are 1.40 and 23.65 cubic centimetres. Calculate titre. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Burette readings are 1.40 and 23.65 cubic centimetres. Calculate titre.
The result is 22.25 cm³. Known: 25.0 cubic centimetres of acid reacts 1:1 with 20.0 cubic centimetres of 0.100 mol per cubic decimetre alkali. n = cV = 0.100×0.0200 = 0.00200 mol. Acid amount is 0.00200 mol. c = n/V = 0.00200/0.0250 = 0.0800 mol per cubic decimetre.
Check the conclusion and its limits
- Adding distilled water to the flask changes volume but not the transferred amount of analyte. Do not average a rough titre with carefully measured concordant values.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
A flask must be rinsed with analyte to avoid dilution of its mole amount. This claim is false: Adding distilled water to the flask changes volume but not the transferred amount of analyte. Do not average a rough titre with carefully measured concordant values.
Titration and a defensible concentration: Calculate the known amount first, apply the stoichiometric ratio, then divide by the unknown solution volume in cubic decimetres. Use concordant titres as required by the school method and report the accepted values.
A flask must be rinsed with analyte to avoid dilution of its mole amount.
Adding distilled water to the flask changes volume but not the transferred amount of analyte. Do not average a rough titre with carefully measured concordant values.
The volume delivered from a burette to reach the stated end-point: write the technical term.
titre means The volume delivered from a burette to reach the stated end-point.