Edexcel Official Chemistry Paper1:Core Inorganic and Physical Chemistry - 27th of May

what did people get for the multiple choice where is asked what happens when ammonium gas and bromine react? i wrote it decolourises

Why would there be a peak at 80 in mass spectrometry of Bromine? There are only two isotopes of bromine- 79 and 81 so why would there be peak at 80?

lets hope brother t-t

This is what I wrote:

In the mass spectrometer, the two isotopes of Br79 ans Br81 combine to form Br2 with a mass of 160, however, the peak at 80 is due to the the charge of the Br2 being 2+ (so the m/z is halved 160/2 = 80) which forms the peak there. However it is very low because there is a very small abundance of that isotope being detected.

What did everyone get for the theoretical amount of gas produced i cant remember the exact question but it was to do with magnesium and HCl

Was it nothing to do with carbon 13?

For the first 6 mark question, I wrote stuff like:

• magnesium ribbon is big, so a lot of gas would be produced so use a smaller ribbon ( that's probably wrong because it said chemicals/ equipment)
• measuring cyclinder has a low resolution so volume might be hard to measure, so use a gas syringe
• the cyclinder was literally on the bed of the water bath, so the gas produced couldn't take up the volume of the cyclinder because the HCl couldn't escape the cycline ( Lol made that up)

For the second 6 marker, I wrote about:

Ionisation energy doesn't really link, but it does link with atomic radius and shielding, which affects how readily oxidized the metal is when reacting with water. So, overall, the rate is affected by atomic radius and it's oxidation ability, but not due to ionisation energy because that only occurs in gases but one can't get a metal gas. Some **** question.

It was definitely helpful, we carried it out under strict examination questions so it will be a true reflection of what we will actually achieve. I am not sure if that's a good thing this late in the course haha!

The questions were slightly different to the past paper and I found the practice paper more difficult then the specimen paper that is available online, so that was useful to get more used to the new style of questions.

I think I got like 40 cm3 for the PV=nRT

Anyone have any ideas on grade boundaries for this year?

I think I got like 40 cm3 for the PV=nRT

How did yiu draw the dot and cross diagram?
And wgat did you answer for Nitrates question? ( why is MgNO3 decompose more readily than some other nitrate)[/QUOTE

The dot and cross diagram is lower down the page here.
http://www.chemguide.co.uk/atoms/bonding/dative.html

For the second part, it was basically about thermal stability and polarisability
• group 1 cations are more stable than group 2 cations
• Mg has a 2+ charge, where as K has a 1+ charge
• Mg 2+ has a smaller atomic radius than K+, so there is a larger electron density in Mg2+
• therefore Mg2+ polarises the carbonate anion more than K+ does
• so Mg(CO3)2 readily decomposes more than KCO3 because it is less thermally stable

I think I got most of it correct. Just a couple of niggling errors such as in that horrid titration question and that balacing which just was hard to do. Second 6 marker wasn't that nice either, although seems I mentioned the poitns others have

The balancing was:

S8 + 8AgF2 -> 4S2F2 + 8AgF