A carless chemistry student pours 200 grams of methanol, a flammable substance into the sink. Another careless chemistry student causes the bad situation to get even worse by dropping a lit match into the sink. The metanol burns completely with 300 grams of oxygen from the air.

A.) approximately what mass, in grams, is converted into energy? (I'm confused on how to justify this because the mass could be anything)

b.) What is the mass of the products in this chemical reaction?

c.) Approximtely what mass, in grams, is converted into different forms of matter?

I need clarification on what happens to the methanol and oxygen that reacts in this chemical reaction?

2 answers

Frankly, I don't think the problem is written very well; however, I think you need to reread the problem. It says, "The methanol burns completely...." which tells me that all 200 g burned.

I don't know how to answer A. The gases will have some heat energy and some kinetic energy. Is this a freshman chemistry course or an advanced course? If an advanced course one could calculate the heat emitted from this reaction fairly easily.

B. 2CH3OH + 3O2 ==> 2CO2 + 4H2O
mols CH3OH = grams/molar mass = ?
mols O2 = grams/molar mass = ?

Using the coefficients in the balanced equation, convert mols CH3OH to mols CO2 and mols H2O.
Do the same for mols O2 to mols CO2 and mols H2O. You will find that mols CO2 and mols H2O are the same for each conversion which means that the exact amount of CH3OH is burned with the exact amount of oxygen which means this is not a limiting reagent problem.

Convert mols CO2 to grams. g = mols x molar mass = ?
Convert mols H2O to grams. g = mols x molar mass = ?

C. Why approximate? Total mass of products = g CO2 + g H2O


2CH3OH + 3O2 ==> 2CO2 + 4H2O

mols methanol = grams/molar mass = ?
mols O2 = grams/molar mass = ?
No this is freshman chemistry so that's why I asked such a question. Thanks for breaking it down. Although, what are the answers to them? kinda confused.