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The amount of ascorbic acid (vitamin C; C6H8O6) in tablets
Chapter 4, Problem 97P(choose chapter or problem)
The amount of ascorbic acid (vitamin \(\mathrm{C}, \mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{6}\)) in tablets is determined by reaction with bromine and then titration of the hydrobromic acid with standard base:
\(\mathrm{C}_{8} \mathrm{H}_{8} \mathrm{O}_{6}+\mathrm{Br}_{2} \rightarrow \mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{8}+2 \mathrm{HBr}\)
\(\mathrm{HBr}+\mathrm{NaOH} \rightarrow \mathrm{NaBr}+\mathrm{H}_{2} \mathrm{O}\)
A certain tablet is advertised as containing \(500 mg\) of vitamin C. One tablet was dissolved in water and reacted with \(\mathrm{Br}_{2}\). The solution was then titrated with \(43.20 mL\) of \(0.1350 \mathrm{M} \ \mathrm{NaOH}\). Did the tablet contain the advertised quantity of vitamin C?
Equation Transcription:
C, C6H8O6
C6H8O6 + Br2 C6H6O6 + 2HBr
HBr + NaOH NaBr + H2O
Br2
Text Transcription:
C, C_6H_8O_6
C_6H_8O_6 + Br_2 rightarrow C_6H_6O_6 + 2HBr
HBr + NaOH rightarrow NaBr + H_2O
500 mg
Br_2
43.20 mL
0.1350 M NaOH
Questions & Answers
QUESTION:
The amount of ascorbic acid (vitamin \(\mathrm{C}, \mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{6}\)) in tablets is determined by reaction with bromine and then titration of the hydrobromic acid with standard base:
\(\mathrm{C}_{8} \mathrm{H}_{8} \mathrm{O}_{6}+\mathrm{Br}_{2} \rightarrow \mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{8}+2 \mathrm{HBr}\)
\(\mathrm{HBr}+\mathrm{NaOH} \rightarrow \mathrm{NaBr}+\mathrm{H}_{2} \mathrm{O}\)
A certain tablet is advertised as containing \(500 mg\) of vitamin C. One tablet was dissolved in water and reacted with \(\mathrm{Br}_{2}\). The solution was then titrated with \(43.20 mL\) of \(0.1350 \mathrm{M} \ \mathrm{NaOH}\). Did the tablet contain the advertised quantity of vitamin C?
Equation Transcription:
C, C6H8O6
C6H8O6 + Br2 C6H6O6 + 2HBr
HBr + NaOH NaBr + H2O
Br2
Text Transcription:
C, C_6H_8O_6
C_6H_8O_6 + Br_2 rightarrow C_6H_6O_6 + 2HBr
HBr + NaOH rightarrow NaBr + H_2O
500 mg
Br_2
43.20 mL
0.1350 M NaOH
ANSWER:
Solution 97P
Here we have to find out did the tablet contain the advertised quantity of vitamin C.
Step 1
In this question it has been given that the amount of ascorbic acid (vitamin C; C6H8O6) in tablets is determined by reaction with bromine and then titration of the hydrobromic acid with standard base, the reaction is given below,
C6H8O6 + Br2 → C6H6O6 + 2HBr
HBr + NaOH → NaBr + H2O
Mass of vitamin C present in tablet = 500 mg
Volume of solution of NaOH = 43.20 mL
Concentration of NaOH = 0.1350 M
In order to calculate the mass of vitamin C, 1st we have to find the moles of NaOH from its given molarity and volume then we will use the molar ratios from the two balanced equations to convert the moles of NaOH to moles of HBr to moles of vitamin C. Finally we have to express the mass of vitamin C in mg.
43.20 mL NaOH
= 5.832
10-3 mol of NaOH