1. The crystal is weighed, and the mass M recorded. The crystal must be a minimum of 0.5 g to be eligible for judging.
2. The quality of the crystal is judged on a scale of 1 to 10, with 10 representing a perfect crystal. The following factors will be considered in judging quality: • match/mismatch with crystal type (out of 2) • presence/absence of occlusions (out of 2) • intact/broken edges (out of 2) • well formed/misformed faces (out of 2) • clarity/muddiness (out of 2) Total Observed Quality Qo = x.xx (out of 10) 3. The Total Score is then determined as follows: Total Score = [log (Mo+1)] x Qo The logarithm of the mass is chosen so that large poor quality crystals don’t swamp out smaller good quality crystals. The value 1 is added to the mass so that crystals weighing less than 1 g get a positive score. A 100 per cent yield crystal made from 100 g (Mt) that scores a perfect 10 on quality (Qt) would get a theoretical maximum of: [log (100+1)] x 10 = 20.01 The actual score is expressed as a percentage of the maximum. The crystal with the highest Overall Score is the winning crystal. 100 x {[log (Mo+1)] x Qo} / {[log (Mt+1)] x Qt} = Overall Score % For example, the best overall crystal in the 2001 contest with 150 g starting material weighed 46.53 g and had a quality of 8.65. Its overall score was: 100 x {[log (46.53+1)] x 8.65} / {[log (150+1)] x 10} = 66.6% This score is nearly an absolute score that could be used to judge different types of crystals grown from differing amounts of starting material.
2.4 Review Questions
2(a) should be CrCl3 3(d) should be mercury (II) chloride Prepare for lab 2D next day. This will be a formal lab. Formal lab report format is attached, and I will also give you a copy of this next class.
2.4 Review Questions
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June 2019
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