[bananafish]

I keep getting the wrong answer, but here is what I have attempted. Where am I going astray?

How many grams of B2O3 (s) are required to produce 10.0 g of B(s)?

This is in equation Mg (s) + B2O3----> MgO (s) + B (s)

OK, so I balanced it to be. 3Mg(s) + B2O3--->3MgO(s) + 2B (s)

So 3 moles + 1 mole ----> 3 moles + 2 moles

10.00 g B               1 mol B           1 mol B2           69.62 g
____________   x ___________ x ____________  x __________

    1                        10.81 g         1 mol B203        1 mol



OK, so I know there is something slightly wrong with this set up but I just don't know where to go from here. It's my first time taking chem and I just can't understand the teacher....everyone I know though has gotten a different answer--9.88 g.

[Borek]

Your conversion factors don't make much sense to me. What is 1 mol of B₂? No such thing, you have 2 moles of B. What is 69.62 g?

And if anyone got 9.88g as an answer they are wrong, so don't worry if your answer is different.

[Fluoroantimonicacid]

It's so silly, 10g B in 9,88g B₂O₃?

[bananafish]

Ok, so

10.00 g B       1 mol B            2 mol B
_________  x  _________  x  _________
   1                 10.81 g          1 mol B203

Is any of this on the right track? Thanks for the hint that their answer is incorrect too--it's so weird, that's what my group came together on, but you are right it does seem really high.

[fledarmus]

Ok, so

10.00 g B       1 mol B            2 mol B
_________  x  _________  x  _________
   1                 10.81 g          1 mol B203

Is any of this on the right track? Thanks for the hint that their answer is incorrect too--it's so weird, that's what my group came together on, but you are right it does seem really high.

The reason you set your conversion factors up in that form is so that you can make sure they cancel. Right now your "mol B" is not going to cancel.

You also still need to convert your "mol B2O3" into grams

[bananafish]

10.00 g B       1 mol B            69.6202 g/mol
_________  x  _________  x  _________
   1                 10.81 g          1 mol


Is this better? I changed B2O3 to grams per mol. Not sure where to from here though!

[fledarmus]

Almost there, but now you've left out the relationship between the number of moles of B on one side of the reaction arrow and the number of moles of B2O3 on the other.