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The flow chart shows a series of steps involved in the production of ethyl butanoate - HSC - SSCE Chemistry - Question 20 - 2005 - Paper 1
Question 20
The flow chart shows a series of steps involved in the production of ethyl butanoate. glucose → mixture containing ethanol → pure ethanol → ethyl butanoate Describ... show full transcript
Worked Solution & Example Answer:The flow chart shows a series of steps involved in the production of ethyl butanoate - HSC - SSCE Chemistry - Question 20 - 2005 - Paper 1
Step 1
Step 1: glucose → mixture containing ethanol
Answer
The first step in the production of ethyl butanoate involves the fermentation of glucose to form ethanol. This is carried out by yeast, specifically Saccharomyces cerevisiae, through the process of anaerobic respiration. The balanced chemical equation for this reaction is:
ightarrow 2 C_2H_5OH + 2 CO_2$$ In this reaction, one molecule of glucose is converted into two molecules of ethanol and two molecules of carbon dioxide. The conditions for fermentation typically include a temperature of around 30°C and an absence of oxygen. Yeast converts the glucose to ethanol, and as it ferments, the gas (CO₂) bubbles off, leaving a mixture containing ethanol, water, and other by-products.Step 2
Step 2: mixture containing ethanol → pure ethanol
Answer
To obtain pure ethanol from the mixture containing ethanol, distillation is employed. In this process, the mixture is heated in a distillation apparatus. The ethanol has a lower boiling point (78.37 °C) compared to water (100 °C), so when heated, the ethanol vaporizes first.
The balanced chemical equation for this can be represented simply as:
ightarrow ext{ethanol (vapor)} ightarrow ext{ethanol (liquid)}$$ The vapors are then collected in a condenser, where they cool and re-condense into liquid form, yielding a higher concentration of pure ethanol.Step 3
Step 3: pure ethanol → ethyl butanoate
Answer
The final step in the production involves the esterification of ethanol with butanoic acid to form ethyl butanoate. This reaction is a condensation reaction that requires an acid catalyst, often sulfuric acid, to proceed efficiently. The balanced chemical equation for this process is:
ightarrow C_5H_{10}O_2 + H_2O$$ In this reaction, one molecule of ethanol reacts with one molecule of butanoic acid to produce one molecule of ethyl butanoate and one molecule of water. This reaction is usually carried out under reflux conditions to ensure that the reactants are heated without loss of volatile components. The resulting ester can be separated and purified through distillation.