help. due tomorrow and Im stuck on the last few.

poshmom

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12 years ago

help. due tomorrow and Im stuck on the last few.

1- A 15.0 g sample of water reacts with PCl3 according to the following equation:

3H2O(l) +PCl3(g)>H3PO3+3HCl(aq)

How many g of H3PO3 are produced?

2- A 25.0g sample of Fe3O4 reacts with O2 to produce Fe2O3:
4Fe2O4(s) + O2(g)>6Fe2O3(s)
Determine the number of g of Fe2O3 produced?

3-If you performed the experiment in #2 and actually obtained 20.3g of Fe2O3, what is the % yield?

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duddy

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12 years ago

Quote from: poshmom (12 years ago)

2- A 25.0g sample of Fe3O4 reacts with O2 to produce Fe2O3:
4Fe2O4(s) + O2(g)>6Fe2O3(s)
Determine the number of g of Fe2O3 produced?

moles Fe3O4 = 25.0g /231.54 g/mol = 0.1079

the ratio between Fe3O4 and Fe2O3 is 4 : 6

moles Fe2O3 = (0.1079 x 6) / 4 = 0.1619590567504535

mass Fe2O3 = 0.1619590567504535 mol x 159.69 g/mol = 25.86324177247992 g

Quote from: poshmom (12 years ago)

3-If you performed the experiment in #2 and actually obtained 20.3g of Fe2O3, what is the % yield?

Use: percent yield = (actual yield / theoretical yield) x 100

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poshmom Author

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12 years ago

Thanks for the video clip. I am having a hard time finding out how you figure our moles/g...

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duddy

wrote...

Staff Member

12 years ago

Quote from: poshmom (12 years ago)

1- A 15.0 g sample of water reacts with PCl3 according to the following equation:

3H2O(l) +PCl3(g) Rightwards Arrow

H3PO3+3HCl(aq)

How many g of H3PO3 are produced?

Use molar mass to find moles:

15.0 grams of H2O @ 18.01 g/mol = 0.832870627429206 moles of H2O

By the equation

PCl3 + 3H2O Rightwards Arrow

H3PO3 + 3HCl

0.832870627429206 moles of H2O produces 1/3 as many moles of H3PO3 = 0.277623542476402 moles H3PO3

using molar mass

0.277623542476402 moles H3PO3 @ 82.00 g/mol =

your answer

22.76513048306496 grams of H3PO3

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