Imagine a particle of dust that masses 25.48ug. What is it's mass in atomic mass units? Round off to appropriate # of significant figures.

The answer given in this physics book (Teqnichally not physics hence the conversion subject) is 1.54e19amu

I seriously don't get where they get this number...my work and ideas are that:

6.022e23amu= 1g
1mg= 0.001g
1ug=0.001mg= 10e-6g

so...based on this that I got in the book

25.48ug(10e-6g/ug)= 2.548e-5g(6.022e23amu/g)=9.22e16amu

As you can see this is NOT the answer given in the book..

For the calculation I used an online scientific calculator b/c I forgot mine at home so...I don't know if I typed something in wrong or it's just me...

help please =)

The atomic mass unit is defined as 1/12 of the mass of one carbon-12 atom. Therefore,
12.00/6.022E23 = y = mass of 1 C-12 atom.

y/12 = conversion unit.
So
[(12.00/6.022E23)/12] = 1.6605E-24 g/amu.

Then 25.48E-6 g x (1 amu/1.6605E-24 g) = 1.534E19 amu.

Google lists the conversion unit as 1.660538E-24g/amu. Typing into google the following
25.48 micrograms to atomic mass units and hit the enter key returns, 1.5344E19.

So I assume that it can't be a conversion using the 1g=____amu?

But is it incorrect that I said that 1g= 6.022e23? b/c that's what is stated in the book I'm using...

However it was stated that 1amu = 1.66054e-24g

Good grief...I still get 9.22e16 when I type it into this stupid scientific calculator online...

and it's not like I can post the link to this ...if it can still be deemed a calculator online since it's "not allowed" (how do you post a link on here?)

And I don't get the conversion of the carbon 12 atom and how you plug it in and...I got lost..

No, 1 g isn't 6.022 X 10^23 (what?), grams? 1 mol is 6.022 x 10^23 atoms or molecules. It IS true that 6.022 x 10^23 amu = 1 gram (that may be what you were saying at the beginning) and if you multiply 6.022 x 10^23 amu/gram x 25.48 x 10^-6 g you get 1.534 x 10^19 which is the answer (more or less) in the book.

Look at the definition. 1 amu is 1/12 the mass of 1 carbon atom.
12.00 g C atoms (1 mol) contain 6.022 x 10^23 atoms of C. So how much does one C atom weigh (I don't mass anything, I weigh it)? It has a mass of 12.000/6.022 x 10^23 = 1.9927 X 10^-23 grams for 1 C atom. The definition says 1/12 of that number (there are 12 nucleons in 1 C atom); therefore,
1.9927 x 10^-23/12.00 = 1.66058 x 10^-24 grams and that is 1 amu.

So you have 25.48 x 10^-6 grams and that times (1 amu/1.66058 x 10^-24) = 1.534 x 10^19 grams.

If you are looking for a conversion factor, the two are
1.66058 x 10^-24 grams/amu AND
6.022 x 10^23 amu/gram

I meant amu...what's with the "what?" I just forgot to type the units but I typed it in at the begining.

I did get that answer when I plugged it into my sane calculator right now...that calculator online has got me extremely stressed since you and the book had the same answer while I had a different one...

I get the carbon to get amu explanation now.

I swear it was that darn calculator online...I typed the eqzn in 4 times...shakes head*

Thanks Dr.Bob

You're welcome! I apologize for any confusion caused by the online calculator. It's always a good idea to double-check your calculations with multiple sources to ensure accuracy. If you have any more questions or need further clarification, feel free to ask!