Chemistry · Oct / Nov 2016 · Paper 22 · Question A4
5070
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A4 Propanone, CH3COCH3, reacts with iodine, I2, to form colourless products. CH3COCH3 + I2 CH3COCH2I + HI The reaction is catalysed by hydrochloric acid. The table shows how the relative rate of this reaction changes when different concentrations of propanone, iodine and hydrochloric acid are used. experiment concentration of CH3COCH3 in mol / dm3 concentration of I2 in mol / dm3 concentration of hydrochloric acid in mol / dm3 relative rate of reaction 1 0.025 0.024 0.12 5.1 2 0.050 0.024 0.12 10.2 3 0.050 0.024 0.06 5.1 4 0.050 0.012 0.06 5.1
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A4(a)[3]
propane: increases (rate)/doubling concentration doubles rate (1)
iodine: no effect (on rate) (1)
hydrochloric acid: increases (rate)/doubling concentration doubles rate (1)
3
A4(b)[2]
particles move faster/particles have more energy (1)
more particles have (energy greater than) the activation energy/more successful collisions (1)
2
A4(c)[1]
atom(s) with same number of protons and different number of neutrons/atom(s) of the same element with different number of neutrons (1)
1
A4(d)[1]
I2 + 2At – → At2 + 2I– (1)
1
A4(e)[1]
they lose electrons/they are oxidised/they give electrons (to hydrogen peroxide)/the oxidation number of iodine increases/the oxidation number of oxygen is decreased (1)
1 Total: 8
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