Question

@surry99

Answer 1

i'm doing a math right now, but just thought I'd post it now in case you want to start on it

Answer 2

@surry99 this is was here_to_help gave me. Could you verify and explain?
Moles H2SO4 = 250 g / 98 g/mol= 2.55 moles O = 2.55 x 4 = 10.2 Mass O = 10.2 mol x 16 g/mol=163.2 g

Answer 3

that is correct...do you fully understand it?

Answer 4

not really...

Answer 5

like, how'd he get the numbers to divide by, such as the 98 g

Answer 6

ok
when I write H2S04 what does that mean to you...ie: how do you interpret that in terms of mols?

Answer 7

2 moles of H. 1 mole os S. 4 moles of O

Answer 8

of, not os*

Answer 9

ok so the way this is interpreted is as follows..
for every 1 mol of H2SO4 you have:
2 mol of H
1 mol of S
4 mol of O...agreed?

Answer 10

right

Answer 11

That's basically what i need. I can't remember what formula is used for what, or the formulas, period

Answer 12

Ah....so we need to teach you some formulas fast...
First formula...n=m/M
number of moles = mass/Molar Mass....you just have to memorize this...
Second point....Molar Mass values are recorded for each element on the periodic table...do you have a copy on your desk?

Answer 13

no, but we are given one for the test. the molar mass is the atomic mass right?

Answer 14

You need a copy of the periodic table to study with...atomic mass = molar mass if I have just one mole.
Go online, and print out a copy of the periodic table and let me know when you have it
and we can continue or pull one up on your monitor

Answer 15

got one

Answer 16

so...lets go through the problem step by step...
you have 250 g of H2SO4....how do you figure out how many mols that is?

Answer 17

um...divide it by the total amount of mols in one gram?

Answer 18

not wait...*sigh* idk

Answer 19

multiply by the total amount of mols in one gram?

Answer 20

n=m/M...
you are given the mass (250 g)
you need to calculate the molar mass of H2S04....this is where you use the periodic table.

Answer 21

now the molar mass by definition is the weight in grams of 1 mol of compound.

Answer 22

so I need the weight in grams of 1 mol of H2S04...
2 mols of H * 1.01 g/mol = 2.02 g of H
1 mol of S * 32.06 g/mol = 32.06 g of S
4 mol of O * 16.0 g/ mol = 64.0 g of O
so the molar mass of H2S04 is 2.02 + 32.06+64 = 98 g

Answer 23

See how I used the atomic masses from the periodic table?

Answer 24

oh, I see. that's where you get the 98g

Answer 25

ok lets keep going ...
calculate for me then if I have 250 g of H2S04 how many mols is that?

Answer 26

2.55?

Answer 27

n=m/M = 250 g/98 g/mol = 2.55 mol
Always write in your units!

Answer 28

Okay. So, then nxt step figuring out how many moles of that is oxygen..?

Answer 29

yes

Answer 30

here is where you use the mol ratio from the compound itself....for every 1 mol of H2S04 how many mol of oxygen do you have?

Answer 31

4

Answer 32

multiply by 4/7 ...?

Answer 33

not quite...you have 4 mol of oxygen for every 1 mol of H2S04...agreed?

Answer 34

agreed

Answer 35

2.55 mol of H2S04 * 4 mol of O/1 mol of H2S04 = 10.2 mol of O
you see what I mean now by writing in the units...

Answer 36

by writing in your units, you can cancel where appropriate and ensure your final answer is in the correct units and that you mol ratios were correct.

Answer 37

Ah. I see.

Answer 38

dimentional analyis,s my teacher calls it

Answer 39

yes...we use it all the time in math, chem, physics etc....very important!

Answer 40

ok, now last step...you have 10.2 mol of O....how many grams is that?

Answer 41

Um....I don't know...in the stuff here-to-help gave me up there ^ he put about 163 or something like that. he multiplied by 16 g, but i don't know where he got that.

Answer 42

n=m/M so rearrange to get

m = n*M ( mass = number of mols * Molar Mass)

Answer 43

number of mols of O is...

Answer 44

10.2 times ah...15.999 (16) = 163.2

Answer 45

i see. Long process...

Answer 46

163.2 g (forgot unit, xD)

Answer 47

yes...but this is the basis of chemistry...working with mass, mols and molar mass
so the first equation to write on your formula sheet is: n=m/M

Answer 48

I copied the process from this problem down in word

Answer 49

and don't forget about having a periodic table available while you do chem.

Answer 50

I won't. :)

Answer 51

Thank you so much.

Answer 52

no problem at all...TTYL

Answer 53

notice you can do this quickly if you use correct dimensional analysis:

(250 g of H2SO4/98 g of H2S04/1 mol of H2S04) * (4 mol of O/1 mol of H2S04)*
16.0 g of )/1 mol of O = 163 g of O