Photo AI
The vapour pressure versus temperature graph below was obtained for four straight chain (unbranched) alkanes (P, Q, R and S) - NSC Physical Sciences - Question 3 - 2017 - Paper 2
Question 3
The vapour pressure versus temperature graph below was obtained for four straight chain (unbranched) alkanes (P, Q, R and S). FROM P TO S, EACH COMPOUND DIFFERES FR... show full transcript
Worked Solution & Example Answer:The vapour pressure versus temperature graph below was obtained for four straight chain (unbranched) alkanes (P, Q, R and S) - NSC Physical Sciences - Question 3 - 2017 - Paper 2
Step 1
3.1 Give a reason why alkanes are said to be SATURATED.
Answer
Alkanes are said to be saturated because they contain only single bonds between carbon atoms. This means that they have the maximum number of hydrogen atoms attached to each carbon, ensuring that there are no double or triple bonds present.
Step 2
Step 3
Step 4
Step 5
3.3.3 Which compound has the longest chain length? Fully explain the answer.
Answer
Compound S has the longest chain length. This is because it is the final compound in the series P to S, which was created by adding -CH₂ groups, thus increasing the carbon chain length as we move from P to S.
Step 6
3.4.1 Draw the structural formula of a chain isomer of P. Write down the IUPAC name of this isomer.
Answer
A chain isomer of compound P can be depicted with a different arrangement of carbon atoms. For example, if compound P is pentane (C5H12), a possible chain isomer is 2-methylbutane. The IUPAC name is 2-methylbutane.
Step 7
3.4.2 How will the vapour pressure of this isomer compare with that of compound P? Choose from HIGHER THAN, LOWER THAN or EQUAL TO.
Answer
The vapour pressure of this isomer will be LOWER THAN that of compound P due to its more branched structure, which typically leads to decreased interactions between molecules and increases the likelihood of them escaping into the vapour phase.