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I'm not an expert teacher or lecturer of chemistry. I was only a student from SMA NEGERI 15 SURABAYA who had been one of the Bronze Medalist Participants of Olimpiade Sains Nasional X (2011) of Chemistry In Manado, North Sulawesi, 11 - 16 September 2011 and graduated in 2012. Now, I'm studying at Universitas Airlangga in Surabaya, Indonesia. I do love chemistry and I would like to help them who had difficulties in studying chemistry. That's why, please understand me if you found some misconcepts in my entries. Suggestions are always necessary in order to develop this blog. And I'm sorry because my English isn't so well.

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The Documents

Tuesday, December 13, 2011

Crystallography Problems

1. In the early days of X-ray crystallography, there was an urgent need to know the wavelengths of X-rays. One technique was to measure the diffraction angle from a mechanically ruled grating. Another method was to estimate the separation of lattice planes from the measured density of a crystal. The density of NaCl is 2.17 g cm-3 and the (100) reflection using Pb K-Alpha radiation occured at 6.0 degree. Calculate the wavelength of the X-rays.

2. The element Polonium crystallizes in a cubic system. Bragg first-order reflections, with X-rays of wavelength 154 pm, occur at sin ϴ = 0.225, 0.316, and 0.388 from (100), (110), and (111) sets of planes. The separation between the sixth and seventh lines in the powder spectrum is larger than between the fifth and sixth lines. Is the unit cell simple, body-centered, or face-centered? Calculate the unit cell dimension.

3. Elemental silver reflects X-rays of wavelengths 154.18 pm at angles of 19.076 degree, 22.171 degree, and 32.256 degree. However, there are no other reflections at angles or less than 33 degree. Assuming a cubic unit cell, determine its type and dimension. Calculate the density of silver.

Source:
Copyright by Aep Patah, Ph.D (Documents of Pelatnas I IChO 2012)


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