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The structure of the cinnamaldehyde molecule is shown - Leaving Cert Chemistry - Question g - 2016
Question g
The structure of the cinnamaldehyde molecule is shown. How many moles of cinnamaldehyde are there in 1.65 g of the pure compound? (Structure of cinnamaldehyde) The... show full transcript
Worked Solution & Example Answer:The structure of the cinnamaldehyde molecule is shown - Leaving Cert Chemistry - Question g - 2016
Step 1
How many moles of cinnamaldehyde are there in 1.65 g of the pure compound?
Answer
To find the number of moles in 1.65 g of cinnamaldehyde:
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Calculate the Molar Mass (Mr):
- C: 12 g/mol
- H: 1 g/mol
- O: 16 g/mol
- Total for C9H8O:
-
Calculate the Number of Moles (n):
- Using the formula:
- Substitute the values:
Step 2
How would you confirm the presence of the sulfite ion in aqueous solution?
Answer
To confirm the presence of the sulfite ion (SO₃²⁻) in an aqueous solution, you can carry out the following test:
-
Add an Acid:
- Introduce a dilute acid such as hydrochloric acid (HCl) to the solution.
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Observe for Gas Evolution:
- If sulfite ions are present, the addition of acid will liberate sulfur dioxide (SO₂), which can be identified by its characteristic smell and by turning acidified potassium dichromate solution from orange to green due to the reduction of Cr₂O₇²⁻ to Cr³⁺.
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Confirmatory Test with Barium Chloride:
- You may also add barium chloride; if sulfite ions are present, a white precipitate of barium sulfite (BaSO₃) may form when reacted with the acidified solution.