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Topic: Eperical formula question.  (Read 6212 times)

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Offline Malgrif

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Eperical formula question.
« on: September 13, 2008, 05:21:01 PM »
Hey, I'm looking for some help with this problem. I've started it but I'm not sure if i'm doing it right or not... It's a multipart question so it's quite long.

Sodium reacts with oxygen to form sodium peroxide.
2Na + 2O ----> Na2O2

a) What is it's emperical formula if it can be made by combining 0.4681 grams of Na with 0.3258 grams of O?

*so I convert the given masses to mols.

0.4681g Na * 1mol/23g= 0.02mol Na

0.3258g O * 1mol/16g= 0.02mol O

*so yeah basically the ratio was 1 to 1 so I wrote Na1O1



b) On this basis, how many grams of sodium can combine with 1.000 grams of oxygen?
*My way of thinking was since the mol ratio was 1 to 1 in this case you would express it as

1.000g O * 1mol/16g * 1mol Na/1mol O * 22g Na/1 mol Na= 1.375g Na

*I'm not sure if i did that right...



c) Another known oxide of sodium is called sodium oxide. Using only your answer to part b, calculate some possible values for grams of Sodium combined with 1.00 gram of oxygen in sodium oxide.
*k so Na2O is what came into my head since I knew Na1O1 you needed 1.375g of Na to combine with 1g of O I simply multiplied that by 2.

1.375g Na * 2 = 2.75g Na would be needed to combine of 1g of oxygen.

*i don't know if my thought process is right or not here.



d) A sample of sodium oxide was found to contain 1.145g of Na and 0.3983g of O. How many grams of Na can combine with 1.000g of O to make sodium oxide.
*Na2O again I don't know what you're suppose to do with the 2 given masses though... so i go the same answer as c, if someone could explain to me how to do this part please.



e) Compare the answers to c and d. What is the ratio of the two masses of sodium that are able to combine with 1.000g of O as they are the two different oxides of sodium? What law of chemical combination is illustrated?
*well can't do this question if i didn't do d right.



f) Calculate the empirical formula of sodium oxide.
*i'm not sure what to do here.


Could someone please solve this and show me and explain the steps for each part... I'm extremely confused right now. Thank you.




Offline dabaichi

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Re: Eperical formula question.
« Reply #1 on: September 13, 2008, 07:26:08 PM »
a) correct
b) atomic mass of Na is 23 not 22.
c) correct method, but error carried forward
d) yea, a repeated question
e) 2Na2O and Na2O2- obviously the Na mass ratio of these are 2:1. This follows the chemical law of multiple proportions.
f) stupid question, just do what you did c.

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