REMEDIAL CHEMISTRY

A student separates a mixture of rock salt (salt and sand).

Step 1: Crush the rock salt, add to warm water, and stir.

Step 2: Filter the mixture through filter paper in a funnel.

Step 3: Heat the filtrate until crystals form.

Which statement about the method is correct?

• The residue in step 2 is sand.
• The filtrate in step 2 is pure water.
• The solute is sand.
• The solvent is salt solution.

A student adds 2.50 g of powdered calcium carbonate to 40.0 cm³ of dilute hydrochloric acid. The reaction produces carbon dioxide gas. Which apparatus is essential to measure the correct quantities of calcium carbonate and hydrochloric acid?

• Pipette and thermometer
• Pipette and burette
• Balance and thermometer
• Balance and measuring cylinder

A student performs a chromatography experiment to separate a mixture containing two substances. The resulting chromatogram is shown. Which diagram correctly shows the measurements and formula used to calculate the Rƒ value?

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The diagrams show the arrangement of carbon dioxide particles in the three states of matter.

• A

• B

• C

• D

Four physical changes of propanol are listed:

(1) freezing

(2) boiling

(3) evaporation

(4) condensation.

In which changes do the particles move further apart?

• 2 and 3
• 1 and 2
• 2 and 4
• 3 and 4

Chromatography is a powerful technique used to separate and identify components in a mixture. The diagram below shows a chromatogram obtained from four dyes P, Q, R, and S. The solvent front reached the top of the chromatogram. Which dye(s) is a pure substance?

• Q only
• S only
• R only
• P, R and S

A student is given a mixture of four colourless, miscible liquids. The boiling points of these liquids are shown in a table. Which method is used to separate the mixture?

• Crystallisation
• Fractional distillation
• Filtration
• Evaporation

Which gas has the fastest rate of diffusion? (Relative molecular masses: Ar = 40, C₂H₆ = 30, HCl = 36.5, H₂S = 34)

• C₂H₆ (30 g)
• Ar (40 g)
• HCl (36.5 g)
• H₂S (34 g)

Each rectangle shows the arrangement of particles in each of the three states of matter. X, Y and Z represent the processes needed to change from one state to another.

• A

• B

• C

• D

The diagram shows the result of dropping a purple crystal into water. After five hours, the liquid becomes a purple solution.

• A

• B

• C

• D