DP Chemistry: MC test: Solar energy

Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.

If you get an answer wrong, read through the explanation carefully to learn from your mistakes.

Which can absorb visible light from sunlight?

II.

III.

I, II and III

I and III only

II and III only

I and II only

In order to absorb visible light the double and single bonds carbon bonds need to show extensive conjugation, i.e. several alternate C=C and C-C bonds.

When photosynthesis occurs what is the ratio of glucose to oxygen that is formed?

1 : 1

1 : 12

6 : 1

1 : 6

The equation is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Other than ethanol, what product is obtained when glucose undergoes fermentation?

oxygen

carbon dioxide

hydrogen

water

The equation is C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

Which is the correct sequence of procedures to obtain almost pure ethanol from starch?

fermentation followed by hydrolysis followed by distillation

hydrolysis followed by distillation followed by fermentation

distillation followed by fermentation followed by hydrolysis

hydrolysis followed by fermentation followed by distillation

Starch must first be hydrolysed to glucose (via maltose) then fermented to give ethanol. However once the ethanol content reaches about 15% it destroys the enzymes in yeast so then it must be distilled. Distillation gives a constant boiling mixture (azeotrope) containing 96% ethanol and 4% water.

Which best describes the following reaction?

RCOOR + C₂H₅OH → RCOOC₂H₅ + ROH (where R ≠ C₂H₅)

transesterification

alkylation

hydrolysis

isomerization

This is an example of transesterification as one of the reactants is an ester and the product is a different ester.

Methyl oleate can be made from the following reaction:

Which statement explains why an excess of methanol is used?

To dissolve the product.

To act as a catalyst.

To move the position of equilibrium to the products side.

To provide the 3 moles of methanol necessary to react with the triglyceride.

Transesterification is an equilibrium reaction and adding excess methanol helps to move the position of equilibrium to give a greater yield of methyl oleate.

Which can be used as a substitute fuel for diesel?

I. H₃C-O-CO-C₁₇H₃₁

II. C₁₇H₃₃COOC₂H₅

III.

I, II and III only

I and III only

I and II only

II and III only

The triglyceride (III) is too viscous to be used as a fuel.

Why is the viscosity of the transester methyl linoleate lower than the triglyceride it can be obtained from?

Glycerol is more viscous than methanol.

Glycerol contains more hydroxyl groups than methanol.

Linoleic acid is an unsaturated fatty acid.

Methyl linoleate has a much lower molecular mass than the triglyceride.

Both are esters but the lower molecular mass of the single ester means it flows much more easily than the triester.

Heating with a strong base such as potassium hydroxide is used to bring about the following reaction.

What is the function of the strong base?

To hydrolyse the ester.

To act as a catalyst.

To form the salt of the fatty acid.

To move the position of equilibrium to the products side.

The hydroxide ions act as a catalyst by removing H⁺ from methanol to release the methoxide ion, OCH₃⁻, which can then act as a nucleophile.

Which best explains why chlorophyll is green

Chlorophyll absorbs red and green light but transmits blue and yellow light which appears green.

Chlorophyll absorbs green light and transmits red and blue light.

Chlorophyll absorbs green light then re-emits it.

Chlorophyll absorbs red and blue light and transmits green light.

The visible absorption spectrum of chlorophyll show that it absorbs red and blue light and transmits green light.

Total Score:

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MC test: Solar energy

Multiple choice test on C.4 Solar energy