Experimental Chemistry – Quiz 2

Q1: The boiling points of various gases found in the air are shown below.

If the air is cooled, the first substance to condense is water.
If the temperature is lowered further, what is the next substance to condense?

Q2: Substance X dissolves in water to form a colourless solution. This solution reacts with aqueous lead(II) nitrate in the presence of dilute nitric acid to give a yellow precipitate.
What is substance X?

Q3: The fractional distillation apparatus shown is to be used for separating a mixture of two colourless liquids. A thermometer is missing from the apparatus.
Where should the bulb of the thermometer be placed?

Q4: The diagram shows a diffusion experiment.

Which gas, when present in the beaker over the porous pot, will cause the water level at Y to
rise?

Q5: The diagram shows four pieces of apparatus that are used to measure the volume of a gas or
liquid.
Which piece of apparatus should always be filled to the same level?

Q6: Aqueous sodium thiosulfate reacts with acid to make a precipitate of sulfur.

Na₂S₂O₃(aq) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + SO₂(g) + S(s)

A student investigates the effect of temperature on the rate of this reaction.

The student:
● places a piece of paper with a cross on it below the reaction mixture as shown in the
diagram
● measures the time taken for the cross to no longer be seen
● repeats the reaction at different temperatures.

Which apparatus is needed for this investigation?

Q7: A paper chromatography experiment is carried out to find an R_f value for Fe³+(aq). The result is
shown.

To make the spot containing Fe³⁺(aq) more visible, the paper is sprayed with aqueous sodium
hydroxide so that a precipitate of iron(III) hydroxide forms.

Under the conditions of the experiment, the R_f of Fe³⁺(aq) is given by ……1…… and the colour of
the precipitate is ……2…… .

Which row correctly completes gaps 1 and 2?

Q8 The diagram shows two experiments.

What are the results of adding an excess of NaOH(aq) in each experiment?

<strong>Q9</strong>: Which methods of separation require a change of state from liquid to gas?

1 paper chromatography
2 crystallisation
3 distillation
4 filtration

Q10: Oxygen was prepared from hydrogen peroxide, with manganese(IV) oxide as catalyst. The
oxygen was collected as shown in the diagram.
2H2O2 → 2H2O + O2

The first few tubes of gas were rejected because the gas was contaminated by

Q11: The labels fell off two bottles each containing a colourless solution, one of which was sodium carbonate solution and the other was sodium chloride solution.
The addition of which solution to a sample from each bottle would most readily enable the bottles
to be correctly relabelled?

Q12: In a titration between an acid (in the burette) and an alkali, you may need to re-use the same
titration flask.
Which is the best procedure for rinsing the flask?

Q1: The diagrams show four different methods of collecting gases.

Which method is suitable for collecting a gas which has the properties described?

Q14: After acidification with dilute nitric acid, a colourless solution of X reacts with aqueous
silver nitrate to give a white precipitate.

What could X be?

Q15: The diagram represents a chromatogram of the colourless acids present in a drink. The
chromatogram has been treated with a locating agent.

A table of R_f values for the possible acids is given.

Which acids are present in the drink?