Chemical analysis test questions

1

Which of the following is not associated with chromatography?

Mobile phase

Separation phase

Stationary phase

2

What is an advantage of thin layer chromatography (TLC) over paper chromatography?

The mobile phase moves more evenly through the stationary phase

The apparatus is cheaper

The absorbencies are constant in the mobile phase

3

Which of the following does not affect how far spots travel up a chromatogram?

The polarity of the molecules

The formula mass of the molecules being separated

The temperature of the solvent used

4

What shows the concentration of compounds present on a gas chromatogram?

The number of peaks shown

The height of the peaks shown

The order the peaks come in

5

In an acid/base titration, where should the acid be?

In the pipette

In a standard flask

In the burette

6

Which of the following titrations would not require an indicator to be used?

Hydrochloric acid and sodium hydroxide

Potassium permanganate and iron sulfate

Vitamin C and iodine

7

What volume of 0.2 mol l^-1 calcium hydroxide (Ca(OH)₂) is required to neutralise 20 ml of 0.4 mol l^-1 sulfuric acid (H₂SO₄)?

20 ml

80 ml

40 ml

8

What is the concentration of sodium sulfite solution, 25 cm³ samples of the solution reacted with an average titre of 15.35 cm³ of 0.01 mol l^-1 acidified potassium permanganate solution.

The redox equation for the reaction is:

\[2MnO{_{4}}^{-}(aq)+6H^{+}(aq)+5SO{_{3}}^{2-}(aq) \rightarrow 2Mn^{2+}(aq)+5SO{_{4}}^{2-}(aq)+3H_{2}O(l)\]

0.015 mol l^-1

0.15 mol l^-1

1.5 mol l^-1

9

Calculate the concentration of an iodine solution if 12.5 cm³ reacts completely with 20 cm³ of 0.1 mol l^-1 sulfite solution.

Reduction:

\[I_{2}(aq)+2e^{-} \rightarrow 2I^{-}(aq)\]

Oxidation:

\[SO{_{3}}^{2-}(aq)+H_{2}O(l) \rightarrow SO{_{4}}^{2-}(aq)+2H^{+}(aq)+2e^{-}\]

0.06 mol^-1

0.16 mol^-1

0.26 mol^-1

10

A 250 cm³ solution of vitamin C (C₆H₈O₆) was prepared by dissolving a tablet in deionised water. A 25 cm³ sample of the solution was titrated against 0.015 mol l^-1 iodine solution, using starch indicator. The average titre was 17.4 cm³.

Calculate the mass of vitamin C in the original tablet, given the gram formula mass of vitamin C is 176 g, and the redox equation:

\[C_{6}H_{8}O_{6}(aq)+I_{2}(aq) \rightarrow C_{6}H_{6}O_{6}(aq)+2H^{+}(aq)+2I^{-}(aq)\]

0.26 g

0.36 g

0.46 g