Page 1.

d(Å)	I(%)
3.86	12
3.035	100
2.845	3
2.495	10
2.284	18
2.095	18
1.927	5
1.913	17
1.875	17
1.626	4
1.604	8
1.587	2
1.525	5
1.518	4
1.510	3

In the diffraction pattern collected, the intensity of the peaks at 2.28 and 1.510Å are larger than expected (29 and 4% respectively) and the large FWHM values (0.43 and 0.42° respectively) suggests there are peaks belonging to other phases with these d spacings and intensities relative to CaCO₃ of 11 and 1 respectively.


(ii)  Normalising the remaining intensities relative to the most intense peak (with d spacing of 3.343Å) gives

d(Å)	I(%)	FWHM(°)
4.27	34	0.27
3.343	100	0.30
2.742	14	0.35
2.503	2	0.36
2.458	12	0.22
2.284	13	0.43
2.237	5	0.23
2.128	10	0.23
2.102	7	0.35
1.980	5	0.23
1.939	2	0.37
1.817	18	0.22
1.700	6	0.35
1.672	7	0.23
1.659	2	0.24
1.541	14	0.23

Comment: Well done spotting that the two lines, 2.28 and 1.510 Å have both an anomalous intensity and large FWHM values and therefore should still be included in the list of remaining lines. For some reason, however, you did include 2.28 but didn't include 1.510 in the list, but I assume this was just a typo.
4.5 Marks

(iii)  Choosing the next 3 highest intensities with d spacings at 3.343, 4.27, 1.817Å and searching the Hanawalt manual gives SiO₂ (card number 5-490) (phase 2.). The card shows peaks with d spacings of 1.541, 2.458, 2.284, 2.128, 1.672, 2.237, 1.980, 1.659Å belong to this phase.

d(Å)	I(%)
4.27	35
3.343	100
2.458	12
2.284	12
2.237	6
2.128	9
1.980	6
1.817	17
1.672	7
1.659	3
1.541	15

Comment: Correct solution and then to follow you compared the patterns in detail and concluded correctly that they matched; there were some lines which didn't appear but this is understandable since they were weak lines (see model answer).
7.5 Marks

(iv)  Normalising the remaining intensities gives

d(Å)	I(%)	FWHM(°)
2.742	100	0.35
2.503	17	0.36
2.102	50	0.35
1.939	17	0.37
1.700	42	0.35
1.510	10	0.42

(v)  Choosing the 3 highest intensities with d spacings of 2.742, 2.102, 1.700Å and searching the Hanawalt manual gives MgCO₃ (card number 8-479) (phase 3.). The card shows that all these peaks belong to this phase.

d(Å)	I(%)
2.742	100
2.503	18
2.318	4
2.103	45
1.939	12
1.769	4
1.700	35
1.510	4

Comment: Correct solution and similar comments to the previous solution.
7 Marks

(vi)  In the diffraction pattern, the patterns of the 3 phases overlap at only two d spacings (2.284Å for phases CaCO₃ and SiO₂ and 1.510Å for phases CaCO₃ and MgCO₃). The background level in the diffraction pattern masks the weaker peaks for the MgCO₃ pattern. The fact that there are no other unaccounted peaks implies that all the phases present have been identified.

Comment: Exactly correct re the overlapping lines. Some comment re the actual solution and that the microprobe analysis is in agreement could have been given (see model answer).
3 Marks

Overall Comment: Basically all the solutions were correct and correct logic was used to arrive at these solutions. I hope this assignment was useful in giving you some further grasp of the procedures involved in search/match analysis.

Total Mark 22