Photosynthesis Practice Questions

Complete the word equation for photosynthesis.

carbon dioxide + .................... $\rightarrow$ .................... + oxygen

Which is the correct balanced symbol equation for photosynthesis?

Put a cross ( ☒ ) in the box next to your answer.

☐ A $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$

☐ B $6CO_2 + 6O_2 \rightarrow C_6H_{12}O_6 + 6H_2O$

☐ C $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$

☐ D $6CO_2 + 12H_2O \rightarrow C_6H_{12}O_6 + 6O_2$

Photosynthesis is described as an endothermic reaction.

State what this tells you about the energy changes in photosynthesis.

Calculate the increase in mass of the willow tree.

Van Helmont concluded that all of the increase in mass of the tree came from the water he added.

Explain why this conclusion is not correct.

Plants such as the willow tree are described as producers.

Explain why.

Which gas do phytoplankton release into the water during photosynthesis?

Put a cross ( ☒ ) in the box next to your answer.

☐ A carbon dioxide

☐ B nitrogen

☐ C oxygen

☐ D water vapour

State two ways the glucose made in photosynthesis is used by a photosynthetic organism.

Very few phytoplankton are found below a depth of 200 m in the ocean.

Explain why.

Calculate the rate of photosynthesis at a distance of 20 cm, in bubbles per minute.

Other than the distance of the lamp from the tube, state two variables the student should have controlled.

The student placed a glass tank of water between the lamp and the boiling tube.

Give the reason for this.

Counting bubbles is not an accurate way of measuring the rate of photosynthesis.

Describe one improvement the student could make to measure the gas produced more accurately.

State the relationship between the light intensity reaching the algal balls and the distance, $d$, of the tube from the lamp.

Calculate the relative light intensity when the tube is 40 cm from the lamp.

Give your answer in arbitrary units.

The student then moved the lamp so that the tube was 20 cm from the lamp.

Explain the effect this would have on the rate of photosynthesis of the algal balls.

A student is asked to investigate the effect of light intensity on the rate of photosynthesis.

The student is given:

• a supply of pondweed
• boiling tubes of pond water containing sodium hydrogencarbonate solution
• a lamp and a metre rule
• a glass tank of water
• a stopwatch and standard laboratory equipment.

Devise a plan the student could use to obtain valid results.

Describe the effect of carbon dioxide concentration on the rate of photosynthesis of these plants.

Explain why the rate of photosynthesis does not increase above a carbon dioxide concentration of 0.12%.

Explain the change in the rate of photosynthesis between 10 °C and 30 °C.

Explain the rate of photosynthesis at 50 °C.

A grower produces lettuce plants inside a large glasshouse in the UK during the winter.

The glasshouse is fitted with lamps, heaters and a burner that releases carbon dioxide. All three can be switched on and off separately.

Explain how the grower should use the lamps, heaters and carbon dioxide burner to obtain the greatest mass of lettuce, using ideas about limiting factors.

Explain why curves A and B are the same at low light intensities.

Explain why curve B levels off at a higher rate of photosynthesis than curve A.

Calculate the rate of oxygen production at a distance of 20 cm, in cm³ per minute.

The student concluded that light intensity was the limiting factor at both distances.

Use the inverse square law and the data in the table to explain whether the results support this conclusion.