Question | Answer |
This question is about hexane, C6H14, and hex-1-ene, C6H12. What test would you use to distinguish between hexane and hex-1-ene Give the results of the test for each substance, | Test : add bromine (water) /bromine solution
bromine gas /bromination (1)
Result: no change with hexane / stays orange brown/ stays red brown/ stays yellow and goes colourless with hex-1-ene(1) OR |
Give the results of the test for each substance, | Test : add (acidified) potassium manganate((VII)(solution)ALLOW potassium permanganate Result: no change with hexane/stays purple
And goes colourless / brown with hex-1-ene (1) OR |
Give the results of the test for each substance, | Test : add alkaline potassium manganate((VII))(solution)(1) ALLOW potassium permanganate
Result: no change with hexane/stays purple and goes green with hex-1-ene (1) |
Explain why stereoisomerism can occur in alkenes, and why hex-2-ene has stereoisomers but hex-1-ene does not | C=C restricts rotation/ C=C prevents twisting /C=C can’t rotate/ lack of free rotation round
C=C (so the groups can’t change position relative to the bond) |
Hex-1-ene has no group which takes priority on the C at one end of C=C &.. | Hex–2-ene has different groups on the C at each |
The value for the enthalpy change of combustion in this experiment is different from the value given in data books. Suggest TWO reasons for this difference | Heat losses (from calorimeter)/ poor insulation • Incomplete combustion/burning •
Evaporation of fuel (after weighing)
heat absorbed by calorimeter.
Heat capacity of calorimeter.
Measurements not carried out under
standard conditions. |
A student suggested that the results would be more accurate if a thermometer which read to 0.1°C was used. Explain why this would not improve the accuracy of the result. A calculation is not required. | Error in reading temperature is less than the effect of ignoring heat loss. |
C6H12(l) + H2(g) → C6H14(l) (i) What catalyst is used in this reaction? | nickel. |
Explain why the values(standard enthalpy change) are so similar | same(number and type of) bonds are broken.
and made in each reaction / one C=C (and one H-H) are broken and two C-H made |
Chloroethae, C2H5Cl, can be made from either ethane or ethene.(i) What reagent and condition would be used to make chloroethane from ethane | Reagent: chlorine/ Cl2 (1) Condition: uv/ sunlight |
State the type of reaction and mechanism by which this reaction occurs | (free) radical (1) Substitution |
What reagent would be used to make chloroethane from ethene | Hydrogen chloride / HCl |
Which of making chloroethane has electrophilic addition a higher atom economy | Higher atom economy from ethene /by Higher yield from ethane |
From ethene | one product / all atoms are used making product /no unwanted products |
For ethene | yield high as no di-, tri- etc substituted products form /only one product / no by-products OR no side reactions occur OR no C4 compounds can form. |
PVC. Almost a quarter of the PVC used to make water pipes,formerly made of metal. Give TWO factors considered when deciding PVC or metal, contributes to more sustainable uses of resources. | Energy for man materials/lifetime of product/how often need replaced /metal rusts/plastic more easily punctured etc • ease of recycling/steel an excellent recyclable material/consequences of disposal/is it biodegradable? from a non-renewable resource? |
The compound butane has the empirical formula | C2H5 and the molecular formula C4H10. |
Avogadro constant 6.0 × 1023 mol–1. Therefore the number of atoms in 1 mol of carbon dioxide is | 1.8 × 1024 |
The enthalpy change for the reaction CH4(g) ---> C(g) + 4H(g) is +1648 kJ mol–1. Hence the mean bond enthalpy for the C–H bond is | / by 4 +412kjmol-1 |
Ethane reacts with chlorine when the substances are exposed to UV radiation. The equation for this reaction | C2H6 + Cl2 --> C2H5Cl + HCl. |
The role of the UV radiation in the reaction is to | break the Cl Cl bond forming Cl• free radicals |