Question

Given the reaction:CO2 + 6 H2O==> C6H12O6 + 6 O2

Answer 1

For every 1 mole of C6H12O6, you need 6 moles of water. Multiply the 2.5 moles you are trying to make by the 6 of water you need, and 4) 15 is your answer.

Answer 2

For every 6 H2O molecules, you can produce 1 C6H12O6 molecule.

Therefore, if you needed to make 2.5 moles of C6H12O6, you would need:
2.5mol C6H12O6*(6mol H2O/1mol C6H12O6)= 15mol H2O

(4) 15 is the correct answer.

Hope this would help~