Experimental Techniques

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• This makes it impossible to calculate Rf values.

• This makes it impossible to use a locating agent.

• This results in a safety hazard caused by solvent fumes.

• This causes the spot nearest the bottom of the paper to catch up with the spot above it.

Naphtha is a fraction obtained from petroleum (crude oil).

Explain how naphtha is obtained from petroleum (crude oil).

• Simple distillation is used. Petroleum is first heated and then cooled down in the condenser. Naphtha is the only product from this distillation.

• Fractional distillation is used. Petroleum is first heated in the fractionating column then cooled down in the condenser. Naphtha can be separated from the other fractions because of their similarity in boiling points.

• Fractional distillation is used. Petroleum is first heated in the fractionating column then cooled down in the condenser. Naphtha can be separated from the other fractions because of their difference in boiling points.

• Fractional distillation is used. Petroleum is cooled down and then heated to separate the fractions. Naphtha can be separated from the other fractions because of their difference in boiling points.

• Simple distillation is used. Petroleum is first cooled down and then heated. Naphtha is the only product from this distillation.

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Benzene and cyclohexane are both flammable liquids. They are able to mix with each other without separating into two layers. They have very similar boiling points. It is difficult to separate a mixture of these two liquids by fractional distillation.

Why is it difficult to separate a mixture of benzene and cyclohexane by fractional distillation?

• They are both flammable.

• They have very similar boiling points.

• They are both liquids.

• They mix with each other completely.

• Ethanol has a higher boiling point than water.

• Ethanol has a lower melting point than water.

• Ethanol has a higher melting point than water.

• Ethanol has a lower boiling point than water.

• Each fraction consists of a single compound.

• Fraction P has the highest boiling point.

• The highest temperature is at the top of the column.

• The naphtha fraction is used as feedstock for the chemical industry.

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The diagrams show four pieces of laboratory equipment.

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During an experiment a measurement is recorded in cm³ . Which apparatus is used?

• balance

• measuring cylinder

• stopclock

• thermometer