Ontario Grade 9 Science Class Practice Exam

What is the equation for photosynthesis?

1. C6H12O6+6O2 -> 6CO2+6H2O

2. 6CO2+6H2O -> C6H12O6+6O2

3. 2H2O -> 2H2 + O2

4. 6H2O+6CO2 -> 6O2+C6H12O6

The correct answer is: 6CO2+6H2O -> C6H12O6+6O2

Photosynthesis is a process in which plants, algae, and some bacteria convert sunlight energy into chemical energy. The equation for photosynthesis is typically written as 6H2O + 6CO2 -> C6H12O6 + 6O2. This means that 6 molecules of water and 6 molecules of carbon dioxide are converted into 1 molecule of glucose (C6H12O6) and 6 molecules of oxygen. Option A is incorrect because it shows the products as 6 molecules of carbon dioxide and 6 molecules of water, which is the reverse reaction. Option C is incorrect because it only shows the decomposition of water, not the overall process of photosynthesis. Option D is also incorrect because it shows 6 molecules of oxygen and 6 molecules of glucose as products, which is the reverse reaction once again.