Question

How many grams are there in 1.00 x 1024 molecules of BCl3?

Answer 1

Answer:

How many grams are there in 1x10^24 molecules of BCl3? I use 117.17 as the molecular weight.

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How many grams are there in 1x10^24 molecules of BCl3? I use 117.17 as the molecular weight.

Did you try approaching this problem with dimensional analysis?

We know:

1×1024 molecules

117.17 g/mol

And we want our answer to be in g.

molecules ×gmolדconversion factor"=g

The conversion factor has to have units of

molmolecules in order for everything to work out.

What property do you know that has units of molmolecules?

I don’t know of any, but I do know that Avogadro’s number has units of moleculesmol. So for our conversion factor, we divide by Avogadro’s number, which is the same thing as multiplying by its inverse.

1×1024 molecules×117.17 gmol×mol6.022×1023molecules=

The “molecules” units cancel. The “mol” units cancel. Leaving us with “g”. The dimensions (units) work out. Now just do the math with the numbers.

Answer 2

Answer:

You need the molecular mass, M , of BCl3.

Explanation:

M = ( 10.81 ) + ( 3 ) ( 35.45 ) = 117.16 g per gmol

You also need the number of gmol of BCl3 :N = [N sub molecules ] / N sub AVO ]

N = [ 1.000 x 10^24 ]/ [ 6.023 x 10^23 ] = 1.660 gmol

You can now get the mass :

--------------------------------------------------------------------

m = ( N ) ( M )

m = [ 1.660 ] [ 117.16 ] = 194.5 g <-----------------------------