I need figure out how many grams of a certain element areneeded to come up with

Question

I need figure out how many grams of a certain element areneeded to come up with a given amount of mass. Here's the officialquestion: How many grams of CO are needed to react with an excess ofFe2O3 to produce 209.7 g Fe? Equation: Fe2O3 + 3CO --> 3CO2 +2Fe I need figure out how many grams of a certain element areneeded to come up with a given amount of mass. Here's the officialquestion: How many grams of CO are needed to react with an excess ofFe2O3 to produce 209.7 g Fe? Equation: Fe2O3 + 3CO --> 3CO2 +2Fe

Explanation / Answer

I need figure out how many grams of a certain element areneeded to come up with a given amount of mass. Here's the officialquestion: How many grams of CO are needed to react with an excess ofFe2O3 to produce 209.7 g Fe? Equation: Fe2O3 + 3CO --> 3CO2 +2Fe

To lay it out in some detail (so you understand why the steps arebeing performed the way they are),
You need 209.7 grams of iron. In a chemical equation, therelationships aren't between grams of different substances -they're between moles of different substances. That means youneed to convert anything in grams to moles.

How do you convert grams to moles? by using the molarmass.

The molar mass of Fe is 55.85 (you get this by looking at theperiodic table).

Therefore if you have 209.7 grams of Fe, and there are 55.85 gramsin a mole, you have
209.7/55.85 = 3.75 mols.

Now you need to determine how many moles of CO you need. Forthis you look at the chemical equation. You see that the ration of CO moles to Fe moles is 3:2. Therefore to make3.75 Fe moles, you need 1.5 x 3.75 = 5.63 moles of CO.

If you know you need 5.63 moles you CO, now you just have toconvert that back into grams. CO is one C atom and one Oatom. So you can look at the periodic table and see that onemole of C atoms weighs 12.01 g and one mole of O atoms weigh 16grams. Therefore 1 mole of CO atoms weigh 12.01 + 16 = 28.01grams.

If you need 5.63 moles of CO and each mole weighs 28.01 grams, youneed 5.63 x 28.01 = 157.8 grams of CO

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