How many grams of water can be made by the reaction of 1.25 grams of ethanol with 2.50 grams of oxygen?
This is a limiting reagent problem. You know that because BOTH reactants are given.
1. Write and balance the equation.
2a Convert 1.25 g ethanol to moles. moles = grams/molar mass.
2b. Convert2.50 g oxygen to moles. same procedure.
3a. Using the coefficients in the balanced equation, convert moles ethanol to moles H2O.
3b. Same procedure, convert moles oxygen to moles H2O.
3c. It is quite likely that the answer to 3a and 3b will not be the same which means one of them is wrong. The correct one is ALWAYS the smaller value and the reactant giving that smaller value is the limiting reagent.
4. Using the value from 3c, convert mols to grams. g = moles x molar mass.