zarkam21:

How much does one sucrose molecule weigh in grams?

3 weeks ago
zarkam21:

342.3

3 weeks ago
Vocaloid:

hm, that would be an entire mole of sucrose, so to find 1 molecule you'd just divide that by avogadro's remember that a molecule is very very small

3 weeks ago
zarkam21:

1.76 x 10^21

3 weeks ago
Vocaloid:

342.3/(6.022*10^23) = ?

3 weeks ago
zarkam21:

5.68 x 10^-22

3 weeks ago
Vocaloid:

good

3 weeks ago
zarkam21:

Find the number of ibuprofen molecules in a tablet containing 200.0 mg of ibuprofen (C13H18O2).

3 weeks ago
zarkam21:

would I find the molar mass first of each element

3 weeks ago
Vocaloid:

yeah, you'd add up 13(molar mass of carbon) + 18(molar mass of hydrogen) + 2(molar mass of oxygen) to find the molar mass of the whole compound then it's 200.0 mg/1000 to convert this to grams; then divide by the molar mass from the first step to get moles, then multiply by avogadro's to get molecules

3 weeks ago
zarkam21:

7.834 x 10^26

3 weeks ago
Vocaloid:

what did you get for the molar mass of ibuprofen

3 weeks ago
zarkam21:

260.1898

3 weeks ago
Vocaloid:

wait no

3 weeks ago
Vocaloid:

the molar mass of ibuprofen should be closer to 206 not 260

3 weeks ago
zarkam21:

yeah i rechecked my calculation I am getting 206.2852 now

3 weeks ago
Vocaloid:

13(12.0107) + 18(1.00794) + 2(15.9994) = 206.28082g

3 weeks ago
Vocaloid:

yeah that's fine, it's within rounding error

3 weeks ago
Vocaloid:

after that it's just ( (200mg/1000) / 206.2852 ) * 6.022e23

3 weeks ago
zarkam21:

5.839 x 10^20

3 weeks ago
Vocaloid:

good that should be your solution

3 weeks ago
zarkam21:

What is the mass of a sample of water containing 3.55×10^22 molecules of H2O?

3 weeks ago
zarkam21:

this would be the opposite right take the molar mass of h20 and multiply by the given

3 weeks ago
Vocaloid:

think about the units of molar mass g/mol; this doesn't have molecules in it since we have molecules we have to convert 3.55×10^22 molecules to moles first, then multiply by the molar mass of water

3 weeks ago
zarkam21:

2.13781 x 10^46

3 weeks ago
Vocaloid:

3.55×10^22 / (6.022e23) * 18.02 = ?

3 weeks ago
Vocaloid:

remember, molecules to moles --> divide by molar mass

3 weeks ago
Vocaloid:

|dw:1539661417976:dw|

3 weeks ago
zarkam21:

1.06

3 weeks ago
Vocaloid:

good that's what i got too

3 weeks ago
zarkam21:

3 weeks ago
Vocaloid:

yeah that's what i got too

3 weeks ago
zarkam21:

What is the mass percentage of each element in the compound Al2O3?

3 weeks ago
zarkam21:

Did you get 9% for Al if I did this right

3 weeks ago
Vocaloid:

hm, I feel like it should be more than that molar mass of aluminum = 26.981538g molar mass of oxygen = 15.9994g total mass: 2(Al) + 3(O) = 2(26.981538g) + 3(15.9994g) just the aluminum: 2(26.981538g) so aluminium only/total mass * 100 should give the percentage

3 weeks ago
zarkam21:

36

3 weeks ago
zarkam21:

and then for O it would be

3 weeks ago
zarkam21:

:

3 weeks ago
Vocaloid:

hm, I got something a bit different

3 weeks ago
zarkam21:

32 for oxygen

3 weeks ago
Vocaloid:

2(26.981538) / [2(26.981538) + 3(15.9994)] = 52.9% composition of aluminum then for oxygen it's just 100% - 52.9% since we only have two components, aluminum and oxygen

3 weeks ago
zarkam21:

Oh I see.

3 weeks ago
zarkam21:

so it would be 52.9 , 47.1

3 weeks ago
Vocaloid:

yes, 52.9 for Al and 47.1 for O

3 weeks ago
zarkam21:

3 weeks ago
zarkam21:

This is what I got. When going from grams to moles, it has nothing to do with avogadros # does it

3 weeks ago
Vocaloid:

not quite have you tried calculating the molar mass of CaCO3?

3 weeks ago
zarkam21:

Yes I got 100.091

3 weeks ago
zarkam21:

and then divided the total by the number of grams given in the problem

3 weeks ago
Vocaloid:

good, so you'd divide 25.45g/100.091g to get to moles, then you'd multiply by 3 since each molecule of CaCO3 has 3 mol oxygen

3 weeks ago
zarkam21:

but I got 48 in the beginning for the molar mass. Would I still multiply by 3?

3 weeks ago
Vocaloid:

48? no the molar mass is 100.091

3 weeks ago
zarkam21:

no I mean when calculating the molar mass of the entire thing I already incorporated oxygen as being 3. In other words 16 * 3 . so why do I need to multiply by 3 again

3 weeks ago
Vocaloid:

you have to incorporate oxygen into the molar mass to get 100.091 after you have moles, you have to multiply by 3 because it's asking for the number of moles of oxygen

3 weeks ago
Vocaloid:

it's a completely separate calculation

3 weeks ago
zarkam21:

oh okay I get it so I have to multiply by 3 in the beginning regardless because of the total molar mass but because its asking for oxygen I have to multiply by 3 again

3 weeks ago
Vocaloid:

yes

3 weeks ago
zarkam21:

.7628

3 weeks ago
Vocaloid:

good that's it

3 weeks ago
zarkam21:

3 weeks ago
Vocaloid:

well you have 100g of the entire compound, and it says its composed of 40.0% carbon, 6.70% hydrogen, 53.5% oxygen, right? so how many grams of carbon hydrogen and oxygen do you have

3 weeks ago
Vocaloid:

still there? since the percentages are out of 100 it's just 40.0g carbon, 6.7g hydrogen, 53.5g oxygen

3 weeks ago
Vocaloid:

then you'd convert these masses to moles

3 weeks ago
zarkam21:

40/100=.4 6.7/100=.067 53.5/100=.535

3 weeks ago
Vocaloid:

hm, that's not how you convert grams to moles, remember g --> moles, divide by molar mass

3 weeks ago
zarkam21:

but would I do 100 divded by molar mass or like the other number for the elements like for carbon 40/molar mass

3 weeks ago
Vocaloid:

we started with 100g of a compound with composition 40.0% carbon, 6.70% hydrogen, 53.5% oxygen naturally, if we want to know the masses of carbons, hydrogens, and oxygen, we would do 100g * 40.0% = 40g of carbon; same reasoning gives us 6.7g hydrogen and 53.5g oxygen

3 weeks ago
Vocaloid:

now, we want to convert 40g of carbon to moles by dividing by the molar mass of carbon, 6.7g hydrogen to moles by dividing by the molar mass of hydrogen and 53.5g oxygen to moles by dividing by the molar mass of oxygen

3 weeks ago
zarkam21:

40/12.011=3.33 6.7/1.0079=6.65 53.5/16=3.34

3 weeks ago
Vocaloid:

awesome, this gives us the molar ratio between the compounds, but since we want whole numbers, we divide all three quantities by the smallest quantity of the three so in simpler words, since the smallest number out of those three is 3.33, divide all three quantities by 3.33

3 weeks ago
Vocaloid:

3.33/3.33 = 1 6.65/3.33 = about 2 3.34/3.33 = about 1 so the molar ratio is CH2O = your empirical formula = your sol'n

3 weeks ago
Vocaloid:

anyway I haven't eaten all day so i'm gonna grab a quick bite, be back in an hour ish if you're still up for more hw

3 weeks ago