How to do Stoichiometry How to do Stoichiometry

The Question The Question

What mass of FeWhat mass of Fe22SS3 3 is produced when is produced when 4.68 grams of Fe reacts with 2.88 4.68 grams of Fe reacts with 2.88 grams of S?grams of S?

Step One Step One

Look at the problem and figure out Look at the problem and figure out how many Stoichiometry problems how many Stoichiometry problems you need to set up.you need to set up.

What mass of FeWhat mass of Fe22SS3 3 is produced is produced when 4.68 grams of Fe reacts with when 4.68 grams of Fe reacts with 2.88 grams of S?2.88 grams of S?

21

Step OneStep One

1 is wrong because you need to find 1 is wrong because you need to find two answers in this equation because two answers in this equation because you are solving for Fe and Syou are solving for Fe and S

GO Back

Step One Step One

Correct the answer is twoCorrect the answer is two In this problem there is two because In this problem there is two because

it is asking for the mass of Feit is asking for the mass of Fe22SS33 so so you need to solve for Iron and Sulfuryou need to solve for Iron and Sulfur

Step Two Step Two

Now you need to set up your problem Now you need to set up your problem for both of your problems too find the for both of your problems too find the answers answers

What mass of FeWhat mass of Fe22SS3 3 is produced when is produced when 4.68 grams of Fe reacts with 2.88 4.68 grams of Fe reacts with 2.88 grams of S?grams of S?

Step TwoStep Two

Which one do you think is the right Which one do you think is the right Stoichiometry equation to find the Stoichiometry equation to find the mass of Femass of Fe22? ?

4.68Fe x 1molFe x 1mol x 207.9gFe2S3

55.85gFe 2molFe 207.9gFe2S3 x 2mol x 1molFe x 4.68Fe

1molFe 55.85gFe

Step TwoStep Two

The second one is wrong because it The second one is wrong because it does not use the right Stoichiometry does not use the right Stoichiometry set upset up

The numbers are mixed up and the The numbers are mixed up and the mole are opposite. mole are opposite.

Go Back

Step TwoStep Two

This answerer is correct it uses all This answerer is correct it uses all the right equations and formula’sthe right equations and formula’s

This problem is ready to be solvedThis problem is ready to be solved

Step Three Step Three

Step three all you need to do is solve Step three all you need to do is solve the problem like a math problem.the problem like a math problem.

So what you do is you multiply across So what you do is you multiply across the numerator and denominator and the numerator and denominator and divide the two numbersdivide the two numbers

4.68Fe x 1molFe x 1mol x 207.9gFe2S3

55.85gFe 2molFe

Step Three Step Three

Use this formula and find out the Use this formula and find out the answerer of how much Fe you would answerer of how much Fe you would get if you had 4.68 grams of Fe and get if you had 4.68 grams of Fe and 2.88 grams of S.2.88 grams of S.

8.71 2.45 9.566.99

Step ThreeStep Three

This answerer is wrong you need to This answerer is wrong you need to make go back and make sure you did make go back and make sure you did it rightit right

Go back and recheck what you did.Go back and recheck what you did.

Step ThreeStep Three

8.71 is correct now all you need to do 8.71 is correct now all you need to do is to find the limiting factor in the is to find the limiting factor in the equation. equation.

Step FourStep Four

Now that you know how to do Now that you know how to do Stoichiometry problems you can find Stoichiometry problems you can find the second answerer your self just the second answerer your self just solve for S now.solve for S now.

Step FourStep Four

What is the limiting factor???What is the limiting factor???

6.22

8.88

2.458.71

Step FourStep Four

This is right 6.22 is the limiting This is right 6.22 is the limiting reactant because it is smaller than reactant because it is smaller than 8.71 8.71

6.22 is your answer now you know 6.22 is your answer now you know Stoichiometry Stoichiometry

Step FourStep Four

This answer is wrong remember the This answer is wrong remember the limiting factor is the smaller numberlimiting factor is the smaller number