If 7.50 grams 1-butene reacts with 25.0 g oxygen how many grams of carbon dioxide will form? Which reactant is limiting? How many grams of excess reactant will be left at the end of the reaction?

Answer 1

How do you know this is a limiting reagent problem. Because BOTH reactants are given, not just one of them.
1. Write the equation and balance it.
2. Convert 7.50 g 1-butene to moles. moles = grams/molar mass.
3. Convert 25.0 g oxygen to moles by the same procedure.
4. Using the coefficients in the balanced equation, convert moles butene to moles either product.
5. Same procedure, convert g oxygen to grams of the (same) product.
6. It is likely that the answer to 4 and 5 will not agree which means one is wrong; the correct answer in limiting reagent problems is ALWAYS the smaller one and the reagent producing that value is the limiting reagent.
7. Now that you have identified the limiting reagent, that means the other reactant is the one that will have an excess. Using the coefficients in the balanced equation, convert moles of the limiting reagent to moles of the "other" reagent, convert that to grams (g = moles x molar mass) and subtract from the initial to find the excess (the amount that did not react).