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a. i - VCE - SSCE Chemistry - Question 9 - 2006 - Paper 1
Question 9
a. i. A long chain carboxylic acid can be represented by the general formula RCOOH where R represents a hydrocarbon group. In the space below, show the structure of ... show full transcript
Worked Solution & Example Answer:a. i - VCE - SSCE Chemistry - Question 9 - 2006 - Paper 1
Step 1
a. i. Show the structure of a fat formed by glycerol and RCOOH
Answer
Palmitic acid (C₁₆H₃₂O₂) is classified as a saturated fatty acid because it does not have double bonds in its hydrocarbon chain. In contrast, oleic acid (C₁₈H₃₄O₂) contains one double bond, making it an unsaturated carboxylic acid.
Step 2
b. Calculate the number of carbon to carbon double bonds
Answer
To find the number of carbon-carbon double bonds in the unsaturated fat, we start by calculating the moles of hydrogen gas:
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Find the molar mass of hydrogen (H):
- Molar mass of H₂ = 2 grams.
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Calculate the number of moles of H₂:
- Moles of H₂ = Mass / Molar mass = 15.0 g / 2 g/mol = 7.5 moles.
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Each double bond will need one molecule of H₂ to saturate it. So, we can use the formula:
ext{Double bonds} = rac{ ext{Moles of H₂}}{2.50 ext{ moles (of unsaturated fat)}}
Hence, the number of double bonds = 7.5 moles / 2.50 moles = 3.0 double bonds.
Step 3
c. Write a balanced equation for the combustion of palmitic acid
Answer
Vitamin C acts as an antioxidant by donating electrons to free radicals, neutralizing them and preventing them from causing cellular damage. This process helps to protect fatty acids and prevents rancidity in margarine by stabilizing the molecular structures against oxidation.