Give the word equation for photosynthesis.
Reveal answer
carbon dioxide + water → glucose + oxygen (light and chlorophyll above the arrow).
Key words: carbon dioxide · glucose
2(e) NUTRITION · RECALL
2.19 Photosynthesis equations
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Give the balanced chemical equation for photosynthesis.
Reveal answer
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Key words: 6CO₂ · C₆H₁₂O₆
Why is light shown above the arrow, not as a reactant?
Reveal answer
Light is a form of energy, not a substance; it is a condition the reaction needs.
Key words: energy
What is meant by the term reactant?
Reveal answer
A starting substance changed during a reaction.
Key words: reactant
What is meant by the term product?
Reveal answer
A substance formed by a reaction.
Key words: product
What is meant by the term coefficient?
Reveal answer
A number placed before a formula to balance relative amounts.
Key words: coefficient
What is meant by the term balanced equation?
Reveal answer
An equation containing equal numbers of each atom on both sides.
Key words: balanced equation
Reading each equation feature: for Coefficients, give the correct interpretation and the common error.
Reveal answer
Correct interpretation: Relative numbers of molecules or moles. Common error: Changing subscripts to balance atoms.
Key words: Coefficients
Reading each equation feature: for Arrow, give the correct interpretation and the common error.
Reveal answer
Correct interpretation: Overall conversion from reactants to products. Common error: Treating it as one-step chemistry.
Key words: Arrow
Reading each equation feature: for Light, give the correct interpretation and the common error.
Reveal answer
Correct interpretation: Energy input or condition. Common error: Calling light a material reactant.
Key words: Light
Reading each equation feature: for Chlorophyll, give the correct interpretation and the common error.
Reveal answer
Correct interpretation: Light-absorbing pigment. Common error: Writing chlorophyll as a consumed reactant.
Key words: Chlorophyll
True or false, and why? “The equation is balanced by changing CO₂ to CO₃.”
Reveal answer
False. Chemical formulae stay fixed; coefficients are changed.
True or false, and why? “Chlorophyll is a reactant.”
Reveal answer
False. It absorbs light and is not consumed in the overall equation.
True or false, and why? “The equation shows one reaction step.”
Reveal answer
False. It summarises many linked reactions.
True or false, and why? “Photosynthesis is simply respiration backwards.”
Reveal answer
False. The overall matter relationship is reversed, but mechanisms and energy pathways differ.