view_agenda
Questions
Find the perfect question by filtering through every previous QCAA Chemistry external exam question
notifications
Question Classifications
We’re conducting a final review of the classifications and formatting for our recently onboarded questions. If you have any feedback, please share it with us here.
QUESTION 23 (5 marks) Aspartame is a methyl ester of a dipeptide that hydrolyses to form methanol and two amino acids. The structure of aspartame is shown. O OCH3 Zz OH NHÔøΩ O a) Identify the two amino acids that form aspartame. [1 mark] A hydrolysed sample of aspartame was analysed with silica thin layer chromatography (TLC) using a mixture of butanol and ethanoic acid as the solvent. The TLC plate was then reacted with ninhydrin to produce spots. Key S = hydrolysed aspartame sample Spot A TTT > R = reference amino acid 1 Spot B R = reference amino acid 2 R; = isoleucine b) Determine which amino acid in aspartame corresponds to Spot A. Explain your reasoning. [3 marks] c) Explain why the reference amino acids are included on the TLC plate. [1 mark]
QUESTION 2 (10 marks) Polypropene (PP) is a polymer formed from propene. Polyethylene terephthalate (PET) is a polymer formed from monomers of carboxylic acid and alcohol. A section of the PET polymer is shown. a) O O \ Ih 7 \ O OÔøΩÔøΩCH ÔøΩÔøΩCH n Draw the structural formulas of the monomers used to form PET. [2 marks] 1) Carboxylic acid monomer 11) Alcohol monomer Note: If you make a mistake in the drawing cancel it by ruling a single diagonal line through your work and use the additional response space on page 16 of this question and response book. Determine the type of polymerisation used to form PET. [1 mark] Identify the functional group formed by the reaction of the monomers in PET. [1 mark] Determine the type of polymerisation used to form PP. [1 mark] Explain how the position of the methyl group on the polymer chain affects the strength of isotactic PP relative to syntactic PP. [5 marks]
QUESTION 4 Which pair of reagents would react to form a glycosidic bond? (A) lysine and aniline (B) glucose and galactose (C) methanol and butanoic acid (D) glycerol and sodium hydroxide
QUESTION 4 (8 marks) Bioethanol is a renewable energy source made from biomasses such as starch and cellulosic materials. The two-step process for the conversion of starch and cellulose to bioethanol is shown. Process | Step 1 Step 2 Conversion | Production to glucose process Starch Enzymatic hydrolysis Fermentation of glucose to Easier Faster (aÔøΩamylase) of starch form bioethanol (yeast) biomass to form glucose Cellulose | Acid hydrolysis (H SO (aq) | Fermentation of glucose to Harder Slower at 320 ÔøΩC and 25 MPa) of form bioethanol (yeast) cellulose biomass to form glucose a) Identify why it is important to control the temperature during the fermentation process to produce bioethanol. [2 marks] b) Explain why cellulose is harder to convert to glucose than starch. [3 marks] c) After 48 hours of fermentation a 15% w/v glucose solution produces 37.5 g L! of ethanol. Calculate the percentage yield of ethanol. Show your working. [3 marks] Ethanol yield = % (to one decimal place)
QUESTION 6 (8 marks) Polypeptides and proteins are formed by condensation reactions of amino acids. a) Identify the type of bond formed when three amino acids are joined to form a tripeptide and state any other product/s formed. [2 marks] b) Determine the total number of tripeptides that can be formed containing histidine lysine and glycine and use the three-letter symbols for the amino acids to describe two of the tripeptides formed. [3 marks] c) Explain how the pH of the buffer solution can be used to separate histidine lysine and glycine through electrophoresis. [3 marks]
QUESTION 6 Identify the reactants that undergo a condensation reaction to produce the molecule shown. O | H;C — CH — CH —C—N— CH — CH — CH | H (A) 1-butanol and propanamine (B) 1-propanol and butanamine (C) butanoic acid and propanamine (D) propanoic acid and butanamine
No results found
open_with
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_1.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_2.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_3.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_4.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_5.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_6.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_7.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_8.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_9.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_10.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_11.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_12.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_13.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_14.webp)
![Formula-Book-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_Formula_Sheet_15.webp)