- #1
waqaszeb
- 11
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Hi guys,
I am doing a lab experiment which involves analysis of a sample of a mixture of NaCl and KCl. I'm using volumetric titration ( Mohrs and Fajans methods) as well a Gravimetric analysis technique. The underlying idea is determine the mass percent of chloride in the same sample using different techniques to see which one is better. The mass percent of the sample, regardless of the method employed, should be similar but the results I found are extremely off. I'm not sure what I am doing wrong.
For example:
For Fajan's method:
Trial 1: 14.31 mL of silver nitrate were needed to reach equivalence point. So I determine the mass(%) chloride in the following way:
14.31 mL/ 1000 x 0.1 M Silver Nitrate = 0.00143 moles of Silver Nitrate
1:1 ratio so the moles of chloride must be equal to the moles of Ag.
moles(chloride)=0.00143 moles x 35.453 g/mol = 0.050 grams?
how is that possible, though? the initial mass of the mixture was 0.1083 grams which was used to make a 250 mL solution. I then did three trials of titration using 25 mL aliquots..each 25mL aliquot should contain 0.01083 grams of mixture...how is it that the mass of just chloride alone is more than mass of the entire mixture. (0.050/0.01083) x 100 = 461% mass. this is obviously wrong. i don't get it :S
In addition, from the gravimetric analysis procedure, I got a mass percent chloride of 58.3. That seems realistic, and I think Fajan and Mohr mass percent should be in that range..not 461% lol. Can anybody help? Thanks!
I am doing a lab experiment which involves analysis of a sample of a mixture of NaCl and KCl. I'm using volumetric titration ( Mohrs and Fajans methods) as well a Gravimetric analysis technique. The underlying idea is determine the mass percent of chloride in the same sample using different techniques to see which one is better. The mass percent of the sample, regardless of the method employed, should be similar but the results I found are extremely off. I'm not sure what I am doing wrong.
For example:
For Fajan's method:
Trial 1: 14.31 mL of silver nitrate were needed to reach equivalence point. So I determine the mass(%) chloride in the following way:
14.31 mL/ 1000 x 0.1 M Silver Nitrate = 0.00143 moles of Silver Nitrate
1:1 ratio so the moles of chloride must be equal to the moles of Ag.
moles(chloride)=0.00143 moles x 35.453 g/mol = 0.050 grams?
how is that possible, though? the initial mass of the mixture was 0.1083 grams which was used to make a 250 mL solution. I then did three trials of titration using 25 mL aliquots..each 25mL aliquot should contain 0.01083 grams of mixture...how is it that the mass of just chloride alone is more than mass of the entire mixture. (0.050/0.01083) x 100 = 461% mass. this is obviously wrong. i don't get it :S
In addition, from the gravimetric analysis procedure, I got a mass percent chloride of 58.3. That seems realistic, and I think Fajan and Mohr mass percent should be in that range..not 461% lol. Can anybody help? Thanks!
