Question

glucose is C6H12O6
a certain ammount of glucose contains 1.26 x10^21 oxygen atoms, what is the mass of glucose?

Answer 1

use avagadros number

Answer 2

@Kystal ihave worked out solution but i don't understand something please help.

Answer 3

@Australopithecus i did

Answer 4

Can you post it form e so I dont have to look it up

Answer 5

this is someone's working..

Answer 6

nevermind I got it 6.02*10^23

Answer 7

number moles O2 = No/NA= 1.26 x10^21/ 6.02 x10^23 = 0.002093mol
number moles glucose: No x 1/6... my problem is that i don't understand where 1/6 came from

Answer 8

6.02*10^23atoms in 1 mole

so we just use unit conversion

\[\frac{1mol}{6.02*10^{23}atoms}* 1.26 x10^{21}atoms\]

Answer 9

the atoms unit cancels out and you are left with moles

Answer 10

yes but thats not what the questions if asking.. @Kystal

Answer 11

please help

Answer 12

k~ i'll give it a try :)

Answer 13

what the question is asking *

Answer 14

Just use the formula

\[Mole = \frac{Grams}{Molecular Mass}\]

Answer 15

what was the amount of moles you got?

Answer 16

@Australopithecus i got 0.002093mol of O2 but we are looking for MM of glucose

Answer 17

number of moles = number of oxygen atoms/ 6.022 x 10^23

Answer 18

Use gravimeter formula

Answer 19

for one mol of glucose u get 6 moles of Oxigen
so n(gluose) = 1/6 n(O)

Answer 20

@Kystal you got that from the formula C6H12O6?

Answer 21

then once u get number of moles.. u use n=m/M

Answer 22

yea~ from the formula~
C6H12O6
the 6 in the formula means there are 6 moles of C and O in the compound~

Answer 23

m(glucose)= 0.063g

Answer 24

\[0.00209mol \frac{180.15g/mol}{(15.9994g/mol)6}\]

this will give you the moles of glucose

to find the molecular mass just add up the grams per mole you find in the periodic table

C has a molecular mass of 12.01g/mol
O has a molecular mass of 15.9994g/mol
H has a molecular mass of 1.00794g/mol

add them up

(12.01)6 + 12(1.00794) + (15.9994)6 = 180.15g/mol

Then sub them into the formula

Answer 25

@Kystal you are awesome! thank you! i was wondering where the 1/6 came from lool

Answer 26

lol~ you're welcome :D

Answer 27

so ig i had SO4 then for 1 mole of SO4 i have 4 moles Oxygen? @Kystal

Answer 28

krystal so smart

Answer 29

yeap :D

Answer 30

krystal can u be my wife? :P

Answer 31

I'm getting 0.703g as the answer

Answer 32

wait nvm 0.706g

Answer 33

using gravimetric factor, assuming we have the moles of 6 oxygen atoms then, I do not see how my assumption could be wrong

Answer 34

spell check always respells gravimetric factor blah

Answer 35

Gravimeteric formula is usually pretty solid and makes sense I'm not sure I follow your solution Kystal

Answer 36

wait nevermind I see but it still doesn't explain the loss in compound in your solution did you do a lot of rounding?

Answer 37

jz listen to krystal method its right

Answer 38

SNSDYoona my method is just as valid

Answer 39

As I'm calculating the ratio of mass between 6O atoms and glucose

Answer 40

but ur method is too complicated.. Krystal method is a simpler way and easier to understand + efficient as it just applies the basics of chemistry

Answer 41

the m(glucose) can be found in 2 ways
since we already know that
n(O)=2.09x10^-3
then
n(C)=n(H)
=2.09x10^-3
n(H)=2n(O)
=4.18x10^-3

method one (calculating separately):
m(glucose)=nM
= (2.09x10^-3)(12.01) + (4.18x10^-3)(1.008)+(2.09x10^-3)(16)
= 0.0628g

method two (calculating all at once):
n(glucose)=1/6n(O)
=nM
=3.48x10^-4 (6x12.01+ 12x1.008 + 6x16)
=0.0628g

Answer 42

@SNSDYoona
Graviametric factor is anything but complicated

I made a mistake in my calculation

\[(0.00209mol*15.9994g/mol)\frac{180.15g/mol}{15.9994g/mol)6} = 0.06275g\]