Question

How many atoms are in 12.53g of Fe(NO3)3

Answer 1

grams to moles first then atoms right

Answer 2

yeah

Answer 3

when it says atoms does it give a specific type of atom?

Answer 4

I think it's a little strange that they're asking for atoms not molecules

Answer 5

okay so I would find the molar mass of Fe(NO3)3 divide it by weight and then multiply by avogadros'

Answer 6

mass/molar mass ---> moles

so 12.53/whatever molar mass

Answer 7

Nope it just says how mant atoms are in 12.53g of Fe(NO3)3

Answer 8

0.05199

Answer 9

I calculated the molar mass of Fe(NO3)3

Answer 10

and did 12.53/241

Answer 11

yeah that should be right (for accuracy I would leave a few more digits on 241, it would be 241.8597g/mol with less rounding)

12.53/241.8597 = 0.05180 moles

then from there, multiplying by avogadro's will give you the # of molecules

Answer 12

since it asks for atoms, not molecules, I ~think~ you would also multiply by 13 since there are 13 atoms in every Fe(NO3)3 molecule but not 100% sure on this

Fe(NO3)3

Answer 13

multiply by 13 before or after

Answer 14

multiplication is commutative so the order doesn't really matter

Answer 15

like before multiply by avogadros or after

Answer 16

true.

Answer 17

4.055 x x 10^24 atoms

Answer 18

yeah that's what i got too

if you have enough time i can double check really quick w/ someone, if not we can move on

Answer 19

Yeah I have time its a hw sheet

Answer 20

we can move on to the next problem, I'll let you know if something needs to be re-done

Answer 21

Okay

Answer 22

How many grams are in 3.30 mol of W?

so

183.85 * 3.30 = 606.705 g

Answer 23

yeah that's what i got too, just after sig figs it's 607g

Answer 24

How many mol are in 1.64 x 10^23 atoms of Pb

so

Answer 25

atoms to moles you divide

Answer 26

so would I do 1.64 x 10^23 / 207.19?

Answer 27

close, atoms to moles ---> divide by avogadro's not the molar mass

Answer 28

since molar mass = g/mole you would either have to start with grams or want to end up with grams, that's not the case here

Answer 29

0.272 mol?

Answer 30

yeah that's what i got too

Answer 31

COmpletely stumped on this if you could just go over how to balance

Answer 32

oh

well this involves some trial and error, but you want to write whole # coefficients such that every element is balanced on both sides (ex. both sides should have the same # of potassium atoms, oxygen atoms, sulfur... etc.)

Answer 33

Well I know that on both sides there is a common divisor

Answer 34

as a general rule you start with the most long/complex-looking compound and try to balance its elements

for example, on your question, I would start with K2SO4. since the right hand side has 2 potassium atoms (K2SO4) and the left side only has 1 (KOH) I put a 2 in front of KOH to balance out the potassiums

Answer 35

coincidentally for this question that completes the balancing (after you write a 2 in front of KOH all the other atoms will be balanced too)

Answer 36

so every other compound just gets a 1 coefficient since we didn't really change those

Answer 37

OH so start from the longest and go from there?

Answer 38

yeah, that's a good rule-of-thumb

Answer 39

OKay sounds good. That is all the work I had for today =) Thank you so much . I appreciate it

Answer 40

awesome

I double checked w/ a friend for that first question and they said it was correct

Answer 41

Great. Thanks

Answer 42

Great. Thanks