Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: chemhuff on January 20, 2005, 11:05:50 PM
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Hi...well, I sincerely say that I am NOT using this forum to get answers! I've tried these problems a million times and can't understand them! I know how to get the limiting reactant, its just the questions really confuse me!! >:(
1. I already balanced the equation:
Fe3O4 + 4H2 ---> 3Fe + 4H2O
Now here's the question: For the equation above, where 11.5g magnetic iron oxide is combined with .450 hydrogen gas, which substance is the limiting reactant?
I'M DUMBFOUNDED!!!! >:( ??? :-X
Here's the last one: (equation already balanced)
For the unbalance equation below, what mass of solid AgCl will precipitate from a solution of 1.50g CaCl2 with excess AgNO3?
CaCl2 + Ag NO3 ---> AgCl + Ca(NO3)2
PLEASE! I SINCERELY ASK FOR *delete me*! ...why do they have to make these questions confusing...urr
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Tell me how many moles of Iron Oxide you have. Then tell me how many moles of Hydrogen you have.
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ok...forgive me if its wrong...i suck at this...for iron oxide, 27.82 mol (?) and for hydrogen 1.3 mol (?)
I multiplied the atomic mass w/the number of atoms then divided it by one mole...is that wrong?
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Lets look at your units.
Atomic weight = grams / mol
# of atoms = (atoms)
moles = moles.
Now this is what you did, you multiplied (grams/mol) and (# of atoms) = grams*#atoms/moles
Then you divided by moles, so the units of that is = grams*#atoms/moles2
That doesn't give you the units of moles, try again.
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ok....urr....is the mol for iron oxide 42.15? and the mol for hydrogen 48.176? 1st, for iron oxide, I multiplied 3 atoms of iron times mole, then 4 atoms of oxygen times mole, and got a total of 42.15 mol for iron oxide. Then I did the same for Hydrogen, 8 atoms*mole....GOD...i think i got it wrong again...
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NO WAIT!! I think I got it this time....number of moles for iron oxide is 18.26, and number of moles for hydrogen is 1.32?
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moles of H2 is 0.225.
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oh, ok...i calculated it wrong...sorry, I had to review the mole concept...so what do I do now?
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How many moles of Iron oxide do you have?
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i said 18.26.....thats wrong?
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I got the answer!! With the help of Tiger....she amazingly tolerated my stupidity in Chemistry :)...the answer for the 1st question is Fe304!! I'm still working on the second question!!
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Tiger should help you out on the board, so all can benefit. ;)
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CaCl2 + 2AgNO3 -> 2AgCl + Ca(NO3)2
given excess silver nitrate added, you can safely assume all the chloride ions present is precipitated out as silver chloride.