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Stoichiometry problem help..?
Im a bit new to chemistry and need some help, so yea, hope someone can send me in the right direction. On a website that im using in conjunction with my textbook, a problem is - How many grams of ferric oxide, Fe2O3, are formed from the reaction of 5.00 g of iron metal with excess oxygen gas? After balancing the equation, and converting into moles.. it gives the equation.. (.0895 - 1 Fe mol/1) x (2 mol Fe2O3/4 mol Fe) which equals .04476 mol Fe2O3. I hope your following still.. so, my question is.. from that equation, how do they get .04476? All help is appreciated.
The website is http://groups.msn.com/ChemistryCorner/stoichiometr... if you found my explaination dodgy. Anyway, all help is appreciated.
3 Answers
- Anonymous1 decade agoFavorite Answer
I will start the question from the beginning:
First you need the equation:
4Fe + 3O2 --> 2Fe2O3
Then work out the masses for the things you need (Fe and Fe2O3)
4*56 g Fe --> 2*(2*56 + 3*16)g Fe2O3
224g Fe --> 320g Fe2O3
Thus 5g Fe will produce
5*320/224 = 7.14g
I have looked at their website and although their method is correct, it is very convoluted.
The reason they get 0.04476 is that 5 g of Fe is 0.0895 moles of Fe. If you look at the equation, you can see that the number of moles of Fe2O3 that is produced is half the number of moles of Fe that react. Therefore they have divided the .0895 by 2 to get the number of moles of Fe2O3.
I have taught chemistry for 30 years and would never go through all these steps for this particular problem. All you need to do is to make sure your equation is balanced, calculate the relevant masses and use direct proportion to work out the answer. No need to calculate the number of moles at all here.
Good luck with your studies
- kendzierskiLv 44 years ago
first ingredient you are able to desire to do is the balancing the equation. that's balanced Moles of Fe produced = 6 moles of CO * (2 moles of Fe / 3 moles of CO) = 4 moles of Fe so Grams of Fe produced = 4 moles of Fe * (fifty 5.80 5 grams of Fe / a million mole of Fe) = 223.4 g of Fe this is the balanced equation C3H8 + 5O2 --> 3CO2 +4 H2O volume of moles of CO2 produced = 25 g of CO2 * (a million mole of CO2 / 40 4 grams of CO2) = 0.5682 moles of CO2 so volume of moles of H2O produced = 0.5682 moles of CO2 * ( 4 moles of H2O / 3 moles of CO2) = 0.7576 moles of H2O so grams of H2O = 0.7576 moles of H2O * (18 grams of H2O / a million mole of H2O) = 13.sixty 4 g of H2O
