SSCE VCE Chemistry Rates of Chemical Reactions: Aspartame is an ingredient in so

Question

Aspartame is an ingredient in some soft drinks. Aspartame is unstable in some conditions and reacts to form four main products. One of the products of aspartame breakdown is 5-benzyl-1,3-dioxo-2-piperazineacetic acid (DKP). It is thought that DKP may be harmful to humans.

A student, Kim, investigates the effect of storage temperature on the rate of production of DKP from aspartame in lemonade. Experimental data is obtained using high-performance liquid chromatography (HPLC) to analyse the aspartame and DKP content in lemonade samples.

HPLC calibration

Kim first calibrated the HPLC using the following method:
1. Prepare and rehydrate a standard solution of pure aspartame with a concentration of 1000 mg L⁻¹.
2. Transfer a 10.00 mL aliquot of the pure aspartame solution into a 1.000 L volumetric flask.
3. Fill the volumetric flask up to the 1.000 L mark with deionised water and shake the flask.
4. Inject a sample of the diluted aspartame solution into the HPLC to obtain a chromatogram.
5. Repeat steps 1–4 with DKP.

The following two calibration chromatograms were obtained.

Analysis of lemonade samples

Kim then followed the method given in steps 6–14 to investigate the rate of production of DKP from aspartame in lemonade at different storage temperatures.

6. Open a can.
7. Transfer a 10.00 mL aliquot of lemonade from the can into a 1.000 L volumetric flask.
8. Fill the volumetric flask up to the 1.000 L mark with deionised water and shake the flask.
9. Inject a sample of the diluted lemonade into the HPLC using the same settings as used during calibration.
10. Set up three water baths at temperatures of 15 °C, 25 °C and 35 °C.
11. Place the unopened can in each of the three water baths. 
12. Record the temperature of the can from each water bath after steps 6–9.
13. After three days, take one can from each water bath and follow steps 6–9.

Aspartame is an ingredient in some soft drinks - VCE - SSCE Chemistry - Question 9 - 2021 - Paper 1

Worked Solution & Example Answer:Aspartame is an ingredient in some soft drinks - VCE - SSCE Chemistry - Question 9 - 2021 - Paper 1

i. rate of production of DKP

ii. change in concentration of DKP (over time)

iii. change in amount of DKP (over time)

Join the SSCE students using SimpleStudy...