Experimental Techniques

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Apparatus for Measurements

Time is measured using a stopwatch or stopclock, accurate to 1 or 2 decimal places; units are seconds or minutes.
Temperature is measured with a thermometer (precision ±0.5 °C) or digital temperature probe (reads to 0.1 °C).
Mass is measured using a digital balance (reads to 2 decimal places); always tare (zero) before use.
Volume of liquid is measured with burettes (most accurate for variable volumes, 0–50 cm³), volumetric pipettes (most accurate for fixed volumes, e.g. 25 cm³), or measuring cylinders (for approximate volumes).
Volume of gas is measured using a gas syringe (more precise) or downward displacement of water (not for soluble gases).
Read the bottom of the meniscus for accurate liquid volume readings; burette scale reads 0.00 cm³ at the top.

Apparatus for measuring volume

Solutions Terminology

Solvent: the liquid in which a solute dissolves (e.g., water in seawater).
Solute: the substance that dissolves (e.g., salt in seawater).
Solution: the mixture formed when a solute dissolves in a solvent (e.g., seawater).
Saturated solution: contains the maximum concentration of solute at a given temperature.
Soluble: a substance that will dissolve (e.g., salt in water).
Insoluble: a substance that will not dissolve (e.g., sand in water).
Filtrate: the liquid that passes through a filter (e.g., fresh coffee in a cup).
Residue: the substance left after filtration, evaporation, or distillation (e.g., coffee grounds).

Acid-Base Titrations: Purpose & Apparatus

Titrations determine the concentration of an acid or alkali by neutralisation.
They can also be used to prepare salts.
Key apparatus: 25 cm³ volumetric pipette, pipette filler, 50 cm³ burette, 250 cm³ conical flask, small funnel, white tile, clamp stand.
A suitable indicator (e.g., methyl orange or phenolphthalein) is used to show the endpoint.

Titration apparatus set-up

Titration Method

1. Use a pipette to transfer exactly 25 cm³ of alkali into a conical flask.
2. Fill the burette with acid using a funnel; run a little through the tap to remove air bubbles.
3. Record the initial burette reading to the nearest 0.05 cm³.
4. Place the flask on a white tile; add a few drops of indicator.
5. Perform a rough titration by adding acid in 1–3 cm³ portions while swirling.
6. Near the endpoint, add acid drop by drop until a sharp colour change occurs.
7. Record the final burette reading; calculate the titre (volume added).
8. Repeat until two concordant results (within 0.1 cm³) are obtained.

Adding indicator and titrating to the endpoint

Common Indicators

Methyl orange: red in acid, yellow in alkali, orange at neutral.
Phenolphthalein: colourless in acid, pink in alkali, colourless at neutral.
Litmus: red in acid, blue in alkali, purple at neutral (not suitable for titrations due to gradual change).
Thymolphthalein: colourless in acid, blue in alkali.

Common Titration Errors

Not removing the funnel from the burette – can cause extra liquid to drip in, giving false high readings.
Not filling the jet space (the part below the tap) – leads to inaccurate volume measurements.
Reading the burette incorrectly – always read from the bottom of the meniscus; scale is 0.0 cm³ at top.
Using a wide-range indicator (e.g., litmus) – does not give a sharp colour change at the endpoint.

Advantages & Disadvantages of Apparatus

Temperature probe: more precise, easy to automate, but can be corroded and expensive.
Volumetric pipette: accurate fixed volume, but harder to use and only one volume.
Gas syringe: easy to set up, keeps gas dry, but can stick, limited volume, fragile.
Microscale experiments: less wasteful, safer, but hard to observe and product loss in purification.

Planning an Experiment

Choose apparatus suitable for the required accuracy and volume.
Ensure the method allows for repeat readings and concordant results.
Consider safety, waste, and time constraints.
Check that the range of measurements is appropriate for the investigation.

Common apparatus for measuring liquid volume

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Übungsfragen

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1.Which piece of apparatus is most accurate for measuring a variable volume of liquid between 0 cm³ and 50 cm³?
Easy
- ABurette
- BMeasuring cylinder
- CVolumetric pipette
- DBeaker
2.Which term describes the liquid in which a solute dissolves?
Easy
- ASolvent
- BSolute
- CSolution
- DFiltrate
3.What is the substance that remains on the filter paper after filtration called?
Easy
- AResidue
- BFiltrate
- CSolute
- DSolution
4.Which indicator is suitable for an acid-base titration?
Easy
- AMethyl orange
- BLitmus solution
- CUniversal indicator
- DRed litmus paper
5.A student needs to measure exactly 25.0 cm³ of sodium hydroxide for a titration. Which apparatus is most appropriate?
Easy
- AVolumetric pipette
- BMeasuring cylinder
- CBurette
- DBeaker
6.Which of the following is a correct step in performing a titration?
Medium
- AAdd indicator before measuring the alkali
- BFill the burette with the solution to be added
- CRecord the final burette reading before the endpoint
- DUse a beaker to measure the alkali
7.A student investigates the rate of reaction between marble chips and hydrochloric acid by measuring the volume of carbon dioxide produced. Which equipment is essential?
Medium
- AGas syringe, conical flask, bung, delivery tube
- BGas syringe, cotton wool, bung, delivery tube
- CGas syringe, beaker, bung, balance
- DBalloon, conical flask, stopper, balance
8.What is the colour of methyl orange in an alkaline solution?
Easy
- AYellow
- BRed
- COrange
- DPink

Mehr Fragen

9.In a titration, why is it important to fill the jet space (the part below the tap) of the burette before starting?
Medium
- ATo give a more accurate result
- BTo avoid air bubbles that cause false readings
- CTo make the titration faster
- DTo ensure the indicator works properly
10.A student prepared crystals of copper(II) sulfate from copper carbonate and sulfuric acid. After filtering, which term describes the copper(II) sulfate solution that passes through the filter paper?
Easy
- AFiltrate
- BResidue
- CSolvent
- DSolute
11.Which of the following changes would improve the accuracy of a titration experiment?
Medium
- AUsing a measuring cylinder to measure the alkali
- BUsing universal indicator instead of a suitable indicator
- CRepeating the titration until concordant results are obtained
- DStarting the burette reading at 0.00 cm³
12.A student wants to measure the volume of gas produced in a reaction. Which method is more precise and accurate?
Medium
- AGas syringe
- BDownward displacement of water
- CInverted measuring cylinder
- DBalloon and balance
13.A student investigates the rate of reaction between magnesium ribbon and dilute hydrochloric acid by measuring the volume of hydrogen gas produced. Which combination of apparatus should be used to collect the gas and measure its volume?
Medium
- AGas syringe, conical flask, bung, delivery tube
- BMeasuring cylinder inverted in water, trough, beaker
- CBurette, conical flask, bung, delivery tube
- DPipette, conical flask, bung, delivery tube
14.A student titrates 25.0 cm³ of sodium hydroxide solution with 0.10 mol/dm³ hydrochloric acid. The average titre is 22.50 cm³. What is the concentration of the sodium hydroxide solution?
Hard
- A0.090 mol/dm³
- B0.111 mol/dm³
- C0.225 mol/dm³
- D0.250 mol/dm³
15.A student records a burette reading as 18.4 cm³ and a measuring cylinder reading as 34 cm³. Which row shows both readings recorded to the correct precision for that apparatus?
Medium
- ABurette 18.4, Measuring cylinder 34
- BBurette 18.4, Measuring cylinder 56
- CBurette 17.8, Measuring cylinder 34
- DBurette 17.8, Measuring cylinder 56
16.Which piece of apparatus is most suitable for accurately measuring a fixed volume of 25.0 cm³ of liquid?
Easy
- AVolumetric pipette
- BMeasuring cylinder
- CBurette
- DBeaker
17.A student wants to investigate the effect of temperature on the rate of reaction between marble chips and hydrochloric acid. They measure the loss in mass over time. Which combination of apparatus is essential?
Medium
- AThermometer, balance, stopwatch
- BThermometer, gas syringe, stopwatch
- CBalance, gas syringe, stopwatch
- DThermometer, measuring cylinder, stopwatch
18.In a titration, a student adds hydrochloric acid from a burette to 25.0 cm³ of sodium hydroxide in a conical flask. Which indicator would give a sharp colour change at the endpoint?
Medium
- AMethyl orange
- BLitmus solution
- CUniversal indicator
- DRed litmus paper
19.A student filters a mixture of sand and salt water. What is the sand called?
Easy
- AResidue
- BFiltrate
- CSolute
- DSolvent
20.The table shows the results of a titration. | | Rough titre | Titre 1 | Titre 2 | Titre 3 | |---|---|---|---|---| | Volume (cm³) | 23.50 | 22.80 | 22.70 | 22.75 | Which value should be used for the accurate titre?
Medium
- A22.75 cm³
- B22.80 cm³
- C22.70 cm³
- D23.50 cm³
21.A student uses a gas syringe to collect carbon dioxide from the reaction of hydrochloric acid and calcium carbonate. After 2 minutes, the gas syringe reads 45 cm³. The reaction stops after 5 minutes with a final volume of 80 cm³. What is the average rate of reaction over the first 2 minutes?
Medium
- A22.5 cm³/min
- B40 cm³/min
- C16 cm³/min
- D45 cm³/min
22.Which of the following is the correct term for the liquid that passes through the filter paper during filtration?
Easy
- AFiltrate
- BResidue
- CSolution
- DSolvent
23.A student is following a procedure that says 'add 25 cm³ of sodium hydroxide quickly'. Which apparatus is most suitable?
Easy
- AMeasuring cylinder
- BVolumetric pipette
- CBurette
- DBeaker
24.A student prepared copper(II) sulfate crystals from copper(II) oxide and dilute sulfuric acid. After filtering, the filtrate is evaporated to obtain crystals. Which term describes the copper(II) oxide that remains on the filter paper?
Easy
- AResidue
- BFiltrate
- CSolute
- DSolvent
25.A student plans to measure 25.0 cm³ of sodium hydroxide for a titration. They use a measuring cylinder. Which statement about this choice is correct?
Medium
- AA measuring cylinder is less accurate than a volumetric pipette for this fixed volume.
- BA measuring cylinder is more accurate than a burette for this fixed volume.
- CA measuring cylinder is the most accurate apparatus for this measurement.
- DA measuring cylinder is as accurate as a volumetric pipette for this fixed volume.
26.A student measures the volume of gas produced in a reaction using a gas syringe and also by downward displacement of water. Which statement is correct?
Medium
- AA gas syringe is more precise and accurate than downward displacement of water.
- BDownward displacement of water is more precise than a gas syringe.
- CBoth methods are equally precise and accurate.
- DA gas syringe cannot be used if the gas is soluble in water.
27.A student performs a titration and obtains the following titres: rough = 23.50 cm³, titre 1 = 22.80 cm³, titre 2 = 22.70 cm³, titre 3 = 22.75 cm³. Which value should be used to calculate the mean titre?
Medium
- A22.75 cm³
- B22.70 cm³
- C22.80 cm³
- D23.50 cm³
28.What is the name for the substance that dissolves in a liquid to form a solution?
Easy
- Asolute
- Bsolvent
- Csolution
- Dfiltrate
29.Which term describes a solution that contains the maximum concentration of solute dissolved at a given temperature?
Easy
- Asaturated solution
- Bconcentrated solution
- Csupersaturated solution
- Ddilute solution
30.A student records the time on a stopwatch as 1:30. What is the correct time in minutes?
Easy
- A1.5 minutes
- B1.30 minutes
- C90 minutes
- D1.3 minutes
31.Which of the following is a common error during a titration?
Medium
- Anot filling the jet space of the burette
- Busing a volumetric pipette to measure the alkali
- Cadding indicator to the conical flask
- Drecording the final burette reading to the nearest 0.05 cm³
32.A student prepares crystals of copper(II) sulfate from copper(II) oxide and dilute sulfuric acid. After filtering, what is the residue?
Easy
- Acopper(II) oxide
- Bcopper(II) sulfate
- Csulfuric acid
- Dwater
33.The solute is the liquid in which a substance dissolves.
Easy
True or false?
34.Match each term (left) with its correct description (right).
Easy
- Filtrate
- Residue
- Solute
- The liquid that passes through a filter
- The substance that remains after filtration
- The substance that dissolves in a solvent
35.In a titration, which indicator gives a colour change from colourless to pink at the endpoint when alkali is added to acid?
Easy
- APhenolphthalein
- BMethyl orange
- CLitmus
- DThymolphthalein
36.A gas syringe is more precise and accurate than downward displacement of water for measuring the volume of a gas produced.
Easy
True or false?
37.Which of the following are common errors during a titration? (Select all that apply.)
Medium
- ANot removing the funnel from the burette
- BFilling the jet space of the burette
- CReading the volume from the top of the meniscus
- DSwirling the conical flask
- ENot filling the jet space of the burette
38.Arrange the following steps in performing a titration in the correct order.
Medium
- Fill the burette with acid using a funnel
- Add a few drops of indicator to the conical flask
- Record the initial burette reading
- Use a pipette to place exactly 25 cm³ of alkali into the conical flask
- Slowly add acid from the burette while swirling until the colour changes
39.A student measures the volume of gas produced in a reaction using a gas syringe. Which of the following is a disadvantage of using a gas syringe?
Medium
- AIt keeps the gas dry
- BIt is easy to set up
- CThe syringe can stick
- DIt is inexpensive
40.Match each term on the left with its correct description on the right.
Easy
- Solute
- Solvent
- Filtrate
- Residue
- The liquid that passes through a filter
- The substance that remains on the filter paper
- The substance that dissolves in a liquid
- The liquid in which a solute dissolves
41.In a titration, 25.0 cm³ of 0.10 mol/dm³ sodium hydroxide is neutralised by 22.50 cm³ of hydrochloric acid. What is the concentration of the hydrochloric acid?
Hard
- A0.111 mol/dm³
- B0.089 mol/dm³
- C0.125 mol/dm³
- D0.225 mol/dm³
42.Complete the sentence:
Easy
A solution that contains the maximum concentration of solute dissolved at a given temperature is called a ____ solution.
43.A stopwatch displays 1:30. What is this time in seconds?
Easy
44.What is the name of the liquid that passes through the filter paper during filtration?
Easy
45.Complete the sentence about indicators.
Easy
Methyl orange is ____ in acid and ____ in alkali.
46.A stopwatch displays 1:30. What is this time in seconds?
Easy
- A90 s
- B99 s
- C108 s
- D81 s

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