EDEXCEL GCSE Chemistry Paper 2 12th June 2019 Unofficial Markscheme

4 +

6.92 for lithium empirical formula

2.25 for mass on MgO

4 + (for the charge)

1x10^-7 for 100 nm

hydrobromic acid - when HBR dissolves in water

the table one was about halogen displacement reactions - iodine is less reactive so gets displaced

6 marker on collision theory :
Concentration: If there is more of a substance in a system, there is a greater chance that molecules will collide and speed up the rate of the reaction. If there is less of something, there will be fewer collisions and the reaction will probably happen at a slower speed.
Increasing the surface area of a solid reactant exposes more of its particles to attack. This results in an increased chance of collisions between reactant particles, so there are more collisions in any given time and the rate of reaction increases.

Nanoparticles do not leave a white mark on the skin - good for sunscreen
however, there hasn't been much research so we don't know long term effects

unsaturated means double bond so can still react with other elements as bond breaks up

in bromine water ethene turns it colourless , poly ethene no as it doesn't have a double bond

kerosene - used for aircraft

kerosene compared to diesel oil - easy ignition, less viscous, low boiling point etc

the one about the Molecular formula for CH2 was C6H12

Test for chlorine - blue ltmus paper turns red then bleaches white

1.5 x 10^21 for the avogadros contant question

In the production of ethanol - can't be 80 degrees or yeast gets denatured

To get the mass of the alcohol needed to change the temp of water: light spirit burner and wait for of water to change by 20 degrees then reweigh the spirit burner and calculate the change in mass

82.7 for carbon in butene

lithium is less reactive than potassium because it has less shells so it would be harder to lose the electron as there is a stronger force of attraction between the nucleus and the outer electron

butane and pentane are neighbours because they differ by a CH2 unit

CO2 levels change due to burning fossil fuels (not always the same amount of co2 released)
deforestation and afforestation (dk if this is righ tho)

6 markers:

When size decreases but conc stays the same volume of gas is higher due to there being larger SA:V ratio. this means the particles around it will have more area to work on increasing rate of reaction etc

When size is constant but conc differs, volume of gas increases with higher conc. this is because there are more particles in the same amount of space increasing the chance of a collision of particles and therefore rate of reaction.

other 6 mark:

Aliminium test. Add excess NaOH to differentiate it from caclium ions. it will turn colourless.

Ammonium test. Damp red litmus paper turns blue

Sulfate test. Add dilute HCl and barium chloride. white precipitate forms.

(think most of this is right)

Howww

i didnt put flame photometry for the lithium and potassium one. I said the bright yellow flame was from the presence of sodium ions and then a lilac flame will be produced (i couldnt think of anything else at the moment). Would that be 1 mark

put the same as you for all except hydrobromic which i wasnt sure! think they are all correct

What do people think a 9s going to be

Not feeling great about the test now looking at the answers :/

Didn’t it say two different ions so I said flame photometer

Most people found the paper quite easy so id assume the grade boundaries will increase

How did everyone do the question with avogadro's constant?

I got 2.4 for the magnesium oxide one

You work out the number of moles of co2 and then you multiply the moles by the constant to get the number of co2 molecules (because 1 mole = 6.02 * 10^23 molecules)

what was the answer?