If you were asked to convert 4.2 X 10^22 atoms of aluminum to moles, which of the following should you use for the conversion?

- anonymous

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- imqwerty

\[\frac{ 4.2 \times 10^{22}}{ N_{A} }\]
N_{A} is the avagadro number

- imqwerty

yea sure :)

- imqwerty

1mole of any substance has 6.022 x 10^23 particles of it

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## More answers

- imqwerty

so 1 mole of Al has 6.022 x 10^23 atoms

- Mertsj

well which one of those is true?
is 6.023x10^23 atoms of Al equal to 13 moles Al

- imqwerty

now if 1 mole has 6.022 x 10^23 atom
then how many mole will have 4.2 x 10^22 atoms :)

- imqwerty

can u calculate how many moles will have 1 atom?

- imqwerty

well just because it has that bad number 26.891... we can't say its wrng we have to give proper reasoning
ok we know that 1mole has 6.022 x 10^23 particles
we need to find how many moles will have 1 particle
so 1st answer this-
6 bags have 3 chocolates
how many bags will have 1 chocolate?

- wolf1728

What's with the mass of aluminum? The origianl question just want number of moles.

- imqwerty

ur saying B is correct cause it has got mass/
nvm its ok :)

- wolf1728

But the original question was just "how many moles is 4.2 x 10^22 atoms".

- wolf1728

There are 6.023 x 10^23 atoms per mole.
You have 4.2 x 10^22 atoms.
4.2 x 10^22 * 1 mole/6.023 x 10^23 atoms

- imqwerty

yes

- wolf1728

Or number 4 in your list

- wolf1728

sure

- wolf1728

2.03 X 10^24 atoms * 1 mole/6.023 x 10^23

- wolf1728

Look carefully at my answer. You don't multiply both numbers.

- imqwerty

number of moles = no of atoms /avagadro number :)

- wolf1728

I made a graphic which shows the calculation more clearly:

##### 1 Attachment

- imqwerty

yes :D

- wolf1728

B it is!!

- wolf1728

okay 1 more question.

- imqwerty

np B)

- imqwerty

moles=mass/molar mass
molar mass of silver=108

- imqwerty

yea correct :D

- wolf1728

Remember to learn how to set it up correctly.
What if you set it up as 107.9/68.3?

- wolf1728

Yes you set it up the right way 68.3/107.9
but you will have to see why.

- wolf1728

The important thing is if you know the correct way to set up the answer because I'm assuming you will be tested on this, right?

- wolf1728

So then you will definitely have to learn how to set up the answer.

- wolf1728

Well imqwerty and myself looked at the answers and we're sure they are correct.

- wolf1728

Atomic mass of copper = 63.55 meaning there are 6.023 x 10^23 atoms for every 63.55 grams of copper.
We need to know atoms in 68.7 grams of copper:
68.7 * 6.023 x 10^23 atoms / 63.55 grams copper
= 6.511 x 10^23 atoms which is C which is your answer

- wolf1728

Moles in 125 g of NI
atomic mass Ni = 58.71 grams per mole
125 grams * 1 mole / 58.71 grams
= 2.129 moles B (which is your answer)

- imqwerty

#(
1mole of silver=108gm=6.022x10^23 particles
\[\frac{ 108\times 5.8 \times 10^{23} }{ 6.022 \times 10^{23}}=mass of (5.8 \times 10^{23})particles\]

- imqwerty

^#9

- wolf1728

I'm working on number 8

- wolf1728

It seems to me you just want correct answers as opposed to HOW to set up the answers.
Question 8 - your answer is wrong.
What is the mass of 25 atoms of mercury? (your answer)

- imqwerty

yes sofia :) thas correct

- wolf1728

So what is your answer for #8?

- imqwerty

np :)
sofia can u tell how did u find out the mass

- imqwerty

nvm :) tell ur method

- wolf1728

Yes it is either B or C for #8

- imqwerty

yes

- imqwerty

ok :)

- imqwerty

yes :D

- imqwerty

np (:

- wolf1728

Did you figure out #8 yet?

- wolf1728

Yes it is C - very good!

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