Class: BE210
Group: R5
Members: FACILITATOR…………………………Toby
Tisserand
TIME & TASK KEEPER………………Elizabeth Kim
SCRIBE………………………………...David Gao
PRESENTER…………………………..Alan Doucette
Date: May, 2001
Abstract:
HCl of known concentration was titrated against a solution of Na2CO3.
Different indicators, including a universal indicator, were used to signal
the stoichiometric equivalence point between carbonic acid [99.9%] and
bicarbonate ion. Agreement of the amount of HCl needed to neutralize
a set amount of Na2CO3 to the amount expected with the measured value to
better than 0.5% was attempted. The pKa values of Na2CO3 were also
determined. The effect of the regulation of temperature on the value
of the equilibrium constants were determined. The percent difference
and confidence intervals were compared to determine the best indicator
for this titration. The 95% confidence intervals were analyzed to
compare the precision of the values obtained under temperature regulation
and non-regulated temperature conditions. In the Na2CO3-HCl titration,
the use of methyl orange as the indicator and the desiccation of Na2CO3
allowed an accuracy of within 0.00501% in the amount of Na2CO3 used in
the titration. The actual amount added was 0.012475 moles, while
the experimentally derived amount was 0.0125 moles with a 95% confidence
interval of ±0.0000460 moles. For Na2CO3 pKa determination,
the pKa1 values for unregulated temperature was 6.362±0.0789; for
regulated temperature pka1 was 6.407±0.0326. They were both
significantly the same as the literature value. However, for pKa2
the unregulated trials measured was 10.45±0.0241, while the regulated
set was 10.37±0.123. They were found to be significantly different
and too imprecise to compare.