- #1
devon
- 21
- 0
1. Ascorbic acid in vitamin tablet
Vitamin tablets with advertised contents including 750 mg ascorbic acid were analysed.
A student took a whole tablet, crushed and dissolved all of it in water. He then diluted the tablet solution to a final volume of 250.0 mL. The student analysed 20.0 mL aliquots of the solution for ascorbic acid by titration using a standardised iodine solution. Data
Final volume containing whole tablet: 250.0 mL
Volume of tablet solution analysed: 20.0 mL
Standard Iodine solution concentration: 0.0198 mol L-1
Average titration volume 17.71 mL
Calculate the mass of ascorbic acid in the tablet. Enter your answer as a whole number of mg.
Attempt: So for this question I calculated the amount of mols of ascorbic acid per 20ml (it is in a 1:1 ratio with iodine) - 0.0198mol/L x 0.01771L = 0.00350658mol. Then I multiplied it by 250ml/20ml (12.5) to find the amount of mols in the entire 250ml solution - 12.5x 0.00350658mol = 0.004383225mol. I then multiplied this by the molar mass of ascorbic acid (176.14g/mol) to get grams of ascorbic acid - 176.14g/mol x 0.004383225mol = 0.7718859225g. I then multiplied this by 1000mg/1g to convert grams to milligrams - 0.7718859225g x 1000mg/1g = 771.8859225mg = 772mg (answer as whole number).
Is this right or did I forget something? I can do all of the math it's just that my problem solving skills aren't that great.2. Ascorbic Acid in Juice
A selection of commercial fruit juices and fruit extracts were analysed for ascorbic acid content.
A student took kiwifruit juice to analyse. This juice is reputed to have ascorbic acid concentrations about 3 times greater than that of orange juice. The student diluted the juice by taking a 25.00 mL sample to a final volume of 100.0 mL. The student analysed 25.00 mL aliquots of the diluted juice solution for ascorbic acid by titration using a standardised iodine solution. Data
Volume juice for dilution: 25.00 mL
Final diluted volume: 100.0 mL
Volume of diluted juice analysed: 25.00 mL
Standard Iodine solution concentration: 0.00496 mol L-1
Average titration volume 18.44 mL
Calculate the concentration of ascorbic acid in the original juice in units of mg / 100 mL. Enter your answer as a whole number of mg
Attempt: I think I know how to do this one but the dilutions at the beginning are throwing me off, I'm not sure if I need to use C1V1=C2V2 to change anything before I start. Regardless this is how I did it:
I calculated the amount of mols of ascorbic acid per 20ml (it is in a 1:1 ratio with iodine) - 0.00496mol/L x 0.01844L = 0.0000914624mol. I then multiplied this by 4 to find the amount of mols in the 100mL solution = 0.0003658496mol/100ml. I then multiplied this by the molar mass of ascorbic acid 176.14g/mol = 0.06444074854g/100ml. I then multiplied this by 1000mg/1g to convert it to milligrams = 64.44074854mg/100ml.
64mg/100ml. I don't know if this is right or not as we did a lab with orange juice and got 72.3mg/100ml. It says the juice is reputed to have though so it could be false.
Sorry for the wall of text, thanks for the help!
Vitamin tablets with advertised contents including 750 mg ascorbic acid were analysed.
A student took a whole tablet, crushed and dissolved all of it in water. He then diluted the tablet solution to a final volume of 250.0 mL. The student analysed 20.0 mL aliquots of the solution for ascorbic acid by titration using a standardised iodine solution. Data
Final volume containing whole tablet: 250.0 mL
Volume of tablet solution analysed: 20.0 mL
Standard Iodine solution concentration: 0.0198 mol L-1
Average titration volume 17.71 mL
Calculate the mass of ascorbic acid in the tablet. Enter your answer as a whole number of mg.
Attempt: So for this question I calculated the amount of mols of ascorbic acid per 20ml (it is in a 1:1 ratio with iodine) - 0.0198mol/L x 0.01771L = 0.00350658mol. Then I multiplied it by 250ml/20ml (12.5) to find the amount of mols in the entire 250ml solution - 12.5x 0.00350658mol = 0.004383225mol. I then multiplied this by the molar mass of ascorbic acid (176.14g/mol) to get grams of ascorbic acid - 176.14g/mol x 0.004383225mol = 0.7718859225g. I then multiplied this by 1000mg/1g to convert grams to milligrams - 0.7718859225g x 1000mg/1g = 771.8859225mg = 772mg (answer as whole number).
Is this right or did I forget something? I can do all of the math it's just that my problem solving skills aren't that great.2. Ascorbic Acid in Juice
A selection of commercial fruit juices and fruit extracts were analysed for ascorbic acid content.
A student took kiwifruit juice to analyse. This juice is reputed to have ascorbic acid concentrations about 3 times greater than that of orange juice. The student diluted the juice by taking a 25.00 mL sample to a final volume of 100.0 mL. The student analysed 25.00 mL aliquots of the diluted juice solution for ascorbic acid by titration using a standardised iodine solution. Data
Volume juice for dilution: 25.00 mL
Final diluted volume: 100.0 mL
Volume of diluted juice analysed: 25.00 mL
Standard Iodine solution concentration: 0.00496 mol L-1
Average titration volume 18.44 mL
Calculate the concentration of ascorbic acid in the original juice in units of mg / 100 mL. Enter your answer as a whole number of mg
Attempt: I think I know how to do this one but the dilutions at the beginning are throwing me off, I'm not sure if I need to use C1V1=C2V2 to change anything before I start. Regardless this is how I did it:
I calculated the amount of mols of ascorbic acid per 20ml (it is in a 1:1 ratio with iodine) - 0.00496mol/L x 0.01844L = 0.0000914624mol. I then multiplied this by 4 to find the amount of mols in the 100mL solution = 0.0003658496mol/100ml. I then multiplied this by the molar mass of ascorbic acid 176.14g/mol = 0.06444074854g/100ml. I then multiplied this by 1000mg/1g to convert it to milligrams = 64.44074854mg/100ml.
64mg/100ml. I don't know if this is right or not as we did a lab with orange juice and got 72.3mg/100ml. It says the juice is reputed to have though so it could be false.
Sorry for the wall of text, thanks for the help!