6. (a) Give the systematic (IUPAC) names for the three hydrocarbon compounds X, Y and Z - Leaving Cert Chemistry - Question 6 - 2010
Question 6
6. (a) Give the systematic (IUPAC) names for the three hydrocarbon compounds X, Y and Z.
(b) Compounds X and Z are obtained from the same fraction in the oil refini... show full transcript
Worked Solution & Example Answer:6. (a) Give the systematic (IUPAC) names for the three hydrocarbon compounds X, Y and Z - Leaving Cert Chemistry - Question 6 - 2010
Step 1
Give the systematic (IUPAC) names for the three hydrocarbon compounds X, Y and Z.
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Answer
X: Heptane
Y: Cyclohexane
Z: Methylbenzene
Step 2
Name the fraction in which X and Z occur.
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Answer
Naphtha / light gasoline / petrol.
Step 3
What two properties of the compounds are responsible for them being found in the same fraction?
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Answer
Similar carbon number (molecular mass).
Similar boiling points.
Step 4
What is meant by auto-ignition in petrol engines?
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Answer
Tendency for premature ignition (explosion) / tendency towards 'knocking' / ignition before spark / ignition before piston reaches top of its ascent.
Step 5
Name the reference hydrocarbon that is the major component of the 83:17 reference mixture.
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Answer
2,2,4-trimethylpentane / iso-octane (italics and hyphen not required).
Step 6
Define heat of combustion.
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Answer
Energy released (heat change) when one mole of a substance is burned (reacts) completely in oxygen / is burned in excess oxygen.
Step 7
Outline how the heat of combustion of X could be measured using a bomb calorimeter.
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Place known amount (mass) of substance in a bomb calorimeter / sample in crucible.
Pressurize with oxygen / burn in excess oxygen / burn completely in oxygen / oxygen inlet labeled in diagram.
Place bomb into known quantity water.
Ignite electrically / ignition coil (wire) labeled in diagram.
Record temperature change using the rise in temperature and the heat capacity of the system / calculate the heat produced using the formula 𝑄 = mcΔ𝑇.
Step 8
Calculate the heat change for this reaction given the heats of formation of C₈H₁₈ and C₇H₁₄ are -224.2 and 124.4 kJ mol⁻¹, respectively.
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