Year 12s: what will be the first way you research your future options? >>

GCSE Urgent!!!! need help !!!!

Ive got over 20 exams to do by the end of the week...ive been ill and unable to do my school work this is got my GCSE bc its teacher assed i rlllly need help with thease two science questions ive done everything else myself i just rlly rlllly need help with thease plsss :frown:

((((((

I need it by 12 tonight

1.Calculate the percentage by mass of oxygen in ammonium nitrate (NH4NO3).
Relative atomic masses (Ar): H = 1 N = 14 O = 16
Relative formula mass (Mr): NH4NO3 = 80

2.Describe a method to investigate how the temperature changes when different masses of ammonium nitrate are dissolved in water.
You do not need to write about safety precautions.

Reply 1

scimus63

work out the Mr of the ammonium nitrate by adding up all the Ar = 14+4+14+48=80
The compound has a mass of 80. There are 3 oxygen atoms in the compound, these have a mass of 16x3 = 48.
So 48 units out of 80 are due to oxygen.
so % by mass of oxygen = 48/80 x100% = 60%

1.collect 5 conical flasks
2. add the same vol of water to each - stir and measure water temp in each
3. add 1g of ammonium nitrate to first conical and stir continually for 2 mins- record temp change.
4. repeat with other conicals but add 2g, then 3g all the way to 5g in the last conical flask.
5. repeat the whole expt and work out average temp change from your 2 experiements