Category: Chemical Engineering Math
"Published in Newark, California, USA"
A mixture of LiBr and BaBr2 weighing 800 mg is treated 50.00 mL of 0.1879 M AgNO3 and the excess is found to require 8.76 mL of 0.3179 M KSCN for back titration, using ferric alum as indicator. What is the percentage of BaBr2 in the sample?
Solution:
If AgNO3 is added to the mixture of LiBr and BaBr2, then the chemical reactions are
Let x = be the amount of LiBr in the sample
y = be the amount of BaBr2 in the sample
Since the amount of LiBr and BaBr2 are unknown, then we need to use two equations, two unknowns.
The first working equation is
By gravimetric analysis, the amount of Br in LiBr is
By gravimetric analysis, the amount of Br in BaBr2 is
From the chemical reactions above, the second working equation is
but 
Hence, the value of y which is the weight of BaBr2 is
Therefore, the percent of BaBr2 in the samples is
Category: Chemical Engineering Math
"Published in Newark, California, USA"
What is the molar concentration of AgNO3 solution standardized against 712 mg primary standard NaCl (58.45 g/mole) requiring 23.8 mL of the solution for titration?
Solution:
The
given word problem is about volumetric analysis in which the titration
of a sample and a solution is involved. If AgNO3 solution is added to NaCl solution, then the white precipitate will be formed which is AgCl. in this titration, potassium chromate is added as the indicator. The end point must be a light red color. If all NaCl molecules are used for the titration, then silver chromate will be formed as a reddish color in the solution. The chemical reaction for the titration is
Therefore, the molar concentration of AgNO3 used to standardize NaCl solution is
Category: Chemical Engineering Math
"Published in Newark, California, USA"
A 5.8734 gram sample of beef was analyzed for N content and the liberated ammonia was collected in a 50.00 mL of 0.4691 M HCl and a 12.55 mL back titration with 0.0256 M NaOH was required. Calculate the percentage protein in the beef sample.
Solution:
The
given word problem is about volumetric analysis in which the titration
of a sample and a solution is involved. By Kjeldahl method, we can
analyze the amount of protein present in any organic samples.
If liberated ammonia is titrated with HCl solution, then the chemical reaction is
and the solution is back titrated with NaOH solution is
The amount of liberated ammonia in a sample is
By gravimetric analysis, the amount of nitrogen present in a sample is
Therefore, the percent of nitrogen or protein in a sample of beef is
