1 These questions are from different areas of chemistry.
(a) Ammonia, NH3
, and ammonium nitrate, NH4NO3
, are compounds of nitrogen.
(i) The boiling
... [Show More] point of NH3
is –33 °C.
The boiling point of NH4NO3
is 210°C.
Explain why there is a large difference in boiling points.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [2]
(ii) Two students discuss the oxidation numbers in ammonium nitrate, NH4NO3
.
One student claims that the two nitrogen atoms have the same oxidation number. The
other student disagrees and claims that the nitrogen atoms have different oxidation
numbers.
Explain with reasons which student is correct.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [1]
© OCR 2022
3
(b) Brass is an alloy of copper and zinc.
The mass spectrum of a sample of brass is shown below.
Relative
abundance
60 61 62 63 64 65
m/z
66 67 68 69 70
The peaks at m/z = 63 and m/z = 65 are from the 63Cu and 65Cu isotopes of copper.
The remaining four peaks are from isotopes of zinc.
(i) What are the percentage compositions of copper and zinc in the brass sample?
Cu = ............. % Zn = .............% [1]
(ii) Calculate the relative atomic mass of zinc in the sample of brass.
Give your answer to 2 decimal places.
relative atomic mass =.........................................................[2]
© OCR 2022 Turn over
45.64%
20.36%
16.82%
9.53% 6.27%
1.38%
4
(c) The structure of an organic compound is shown below.
The protons are in four different environments, which are labelled 1–4.
1
H3C
2 3
CH2 CH2
O
C C
O H
4
(i) Fill in the table to predict the splitting patterns in the proton NMR spectrum of the
organic compound.
Proton environment Splitting pattern
1
2
3
4
[2]
(ii) The table shows the chemical shifts for the peaks in the proton NMR spectrum at
proton environments 2 and 3.
Proton environment 2 3
Chemical shift, δ 2.5ppm 3.6ppm
Suggest why the peaks for proton environments 2 and 3 have the chemical shifts which
are shown in the table.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [2]
© OCR 2022
5
(d) Glycine, H2NCH2COOH, is an α-amino acid.
(i) Glycine reacts with NaOH to form the salt H2NCH2COONa.
Glycine reacts with HCl to form the salt HOOCCH2NH3Cl.
The salts have different H–N–H bond angles.
State the different H–N–H bond angles and explain why they are different.
H2NCH2COONa H–N–H bond angle = ..................°
HOOCCH2NH3Cl H–N–H bond angle = ..................°
explanation ........................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [3] [Show Less]