O Level 5067 State of matters and Separating Substances

The rate of diffusion of gas X (Mr = 17) and gas Y (Mr = 28) was compared at 25⁰C and 50⁰C.

Which would have the fastest rate of diffusion?

• Gas X at 25⁰C

• Gas X at 50⁰C

• Gas Y at 25⁰C

• Gas Y at 50⁰C

A student accidentally mixed 50cm³ of water with 50cm³ of oil.

Which method would allow him to obtain 25cm³ of the oil most easily?

• chromatography

• evaporation

• filtration

• use of separating funnel

A series of experiments was carried out in order to determine how the rate of reaction of magnesium with hydrochloric acid varied with the concentration of the acid. In each experiment, excess magnesium was reacted with 50 cm³ of hydrochloric acid in a conical flask.

Five other pieces of apparatus were available.

(attached)

Which four pieces of apparatus would be needed to carry out the experiment?

• 1, 2, 3 and 4

• 1, 2, 3 and 5

• 1, 3, 4 and 5

• 2, 3, 4 and 5

The apparatus shown is used to distil ethanol (boiling point 78⁰C) from a mixture of ethanol and water.

(attached)
Which graph shows the change in concentration of the ethanol in flask F as the distillation proceeds?

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A paper chromatogram was prepared using a mixture of substances. After drying, the chromatogram is shown in the diagram.

(attached)
Which statement is correct?

• Locating agents are always needed to interpret a chromatogram

• The chromatography paper must have been placed with the solvent below level Z

• There must have been two substances present in the mixture

• The substances at level X has a lower Rf value than the substance at level Y

Three separations are listed.

1) obtaining water from sodium chloride solution

2) obtaining iodine from a mixture of iodine and nickel

3) obtaining solid sodium chloride from aqueous sodium chloride

Which techniques would be involved in these separations?

• 1) distillation

  2) sublimation

  3) evaporation

• 1) distillation

  2) sublimation

  3) filtration

• 1) filtration

  2) crystallisation

  3) evaporation

• 1) sublimation

  2) crystallisation

  3) filtration

Magnesium ribbon was reacted with excess dilute hydrochloric acid.

The graph shows the volume of hydrogen gas evolved at 20 second intervals until the reaction had finished.

Which piece of apparatus would be suitable for measuring the volume of hydrogen gas evolved?

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Which physical processes could be used to separate diesel and water?

1) distillation

2) filtration

3) sublimation

4) use of a separating funnel

• 1, 2, 3 and 4

• 1, 2 and 3 only

• 1 and 2 only

• 1 and 4 only

Which row correctly shows the order of the rates of diffusion of the gases ammonia, carbon dioxide and hydrogen bromide?

(from slowest to fastest)

• CO₂ - HBr - NH₃

• HBr - CO₂ - NH₃

• HBr - NH₃ - CO₂

• NH₃ - CO₂ - HBr

The stopper was removed from a bottle containing perfume X and the time taken for the smell to reach the opposite side of the room was noted.

The experiment was repeated using perfume Y. Perfume Y has a higher relative molecular mass than perfume X.

Which gives:

- the name of the process by which the perfume spreads around the room

- the identity of the perfume that reaches the opposite side of the room in the shorter time?

• name of the process: diffusion

  perfume reaching opposite side of room in shorter time: perfume X

• name of the process: diffusion

  perfume reaching opposite side of room in shorter time: perfume Y

• name of the process: evaporation

  perfume reaching opposite side of room in shorter time: perfume X

• name of the process: evaporation

  perfume reaching opposite side of room in shorter time: perfume Y