1) The shorter hydrocarbons are more useful as they are easier to ignite and less viscous (they flow more easily)
2) Shorter, longer, longer, shorter, longer, shorter
There is a greater demand for shorter hydrocarbons compare to longer hydrocarbons. There is a greater supply than demand for longer hydrocarbons. There is greater demand than supply for shorter hydrocarbon. Cracking breaks down a longer hydrocarbon into shorter hydrocarbons.
b) Thermal decomposition reaction (this means that a substance breaks down with heat)
4) Heat up the hydrocarbons that you want to crack so that they turn into a gas (vaporise them)
Pass the vaporised hydrocarbons over a powdered catalyst (sometimes aluminium oxide)
Thermal decomposition occurs and the long hydrocarbon splits up into smaller hydrocarbons
C12H26 –> C10H22 + C2H4
b) Create polymers
c) C12H26 –> C9H20 + C3H6
C10H22 –> C7H16 + C3H6
1) Out of shorter and longer hydrocarbons, which are more useful? Explain your answer.
2) Fill in the gaps below with the words “shorter” and “longer”.
There is a greater demand for _______ hydrocarbons compare to _______ hydrocarbons. There is a greater supply than demand for _______ hydrocarbons. There is greater demand than supply for _______ hydrocarbon. Cracking breaks down a _______ hydrocarbon into _______ hydrocarbons.
a) Is cracking an exothermic or endothermic reaction?
b) What type of reaction is cracking?
4) Describe the steps in catalytic cracking.
5) The cracking of dodecane (C12H26) produces ethene (C2H4) and one other hydrocarbon. The partially completed chemical equation is shown below.
C12H26 –> _______ + C2H4
a) Find the molecular formula for the other hydrocarbon.
b) Give one use for the ethene that is produced by cracking dodecane.
c) A different molecule of dodecane is cracked. This time it produces propene (C3H6) and one other hydrocarbon. Write the balanced chemical equation for this taking place.
6) The cracking of decane (C10H22) produces heptane (C7H16) and one other hydrocarbon. The partially completed chemical equation is shown below.
C10H22 –> C7H16 + ______
Complete the chemical equation.
7) Is the statement below true or false?
“cracking is used to match supply with demand”