Can someone please help me with these chemistry problem. Thanks.

Chemistry
Tutor: None Selected Time limit: 1 Day

An unknown compound is analyzed and found to be composed of 14.79% nitrogen, 50.68% oxygen, and 34.53% zinc. Calculate the empirical formula for the compound.
May 6th, 2015

Let us consider 100 g of compound.

Mass of nitrogen=14.79g

Moles of nitrogen=14.79/14=1.056mol

Mass of oxygen=50.68g

Moles of nitrogen=50.68/16=3.1675mol

Mass of zinc=14.79g

Moles of nitrogen=34.79/65=0.532mol

Simple ratio,

N:O:Zn=1.056:3.1675:0.532

=2:6:1

Empirical formula=ZnN2O6


May 6th, 2015

Would the answer change if zinc is 34.53%.

May 6th, 2015

zinc is already 34.53%, any composition change may result in change of formula.

May 6th, 2015

When I'm looking at the problem you worked out I see that you put zinc at 14.79 why is that, should it not be 34.53.

May 6th, 2015

Oh! that is just a typo error, next line I have taken it 34.53. It should have been 34.53 g.

May 6th, 2015

Ok thanks I don't see it I see 34.79 I needed 34.53. Thank you for your help.

May 6th, 2015

Let us consider 100 g of compound.

Mass of nitrogen=14.79g

Moles of nitrogen=14.79/14=1.056mol

Mass of oxygen=50.68g

Moles of nitrogen=50.68/16=3.1675mol

Mass of zinc=34.53g

Moles of nitrogen=34.53/65=0.531mol

Simple ratio,

N:O:Zn=1.056:3.1675:0.531

=2:6:1

Empirical formula=ZnN2O6

………………………………………………………………………

A very small change in mass doesn’t reflect in empirical formula.


May 6th, 2015

Sorry how is O6 and not O3

May 6th, 2015

Because, 3.1675/0.531=5.97 equivalent to 6. So, every no need to be converted to integar.

May 6th, 2015

Okay thank you so much. Can I pay you for your troubles.

May 6th, 2015

Ya, is you wish. I would be very happy to help you again.

May 6th, 2015

do you have more doubt? Plz contact me on message.

May 6th, 2015

No thank you I am just working it out to see if I come up with the same answer you did.

May 6th, 2015

kk

May 6th, 2015

My final answer was N:1.0552 O:3.1677 ZN:0.5280

NO3Zn

I am dividing all the numbers by 1.0552

May 6th, 2015

No. Always divide by smallest number, ie 0.5280. And round it to nearesnearest integar. 

May 6th, 2015

Ok thank you will rework my problem.

May 6th, 2015

Plz message me for more help. 

May 6th, 2015

Ok thank you for your help. I finally got the same answer you have. How do I pay you?

May 6th, 2015

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