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Answers to midterm 2 - n^T fiL 6 v t CG,ttt^ 1(10 poinfs Platinum(symbol Pt has a density of 21 4 g cm-a It is observed that X-ray radiation of

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Unformatted text preview: n^T fiL 6 v t CG,ttt^) 1. (10 poinfs) Platinum (symbol Pt) has a density of 21 4 g cm-a. It is observed that X-ray radiation of 264pm is scattered in phase by u sample of platinum at an angle of 25o. What type of cubic unit cell is this sample of platinum using? You must show calculations to prove your answer. Fo, {k ',.s t^t i l +atu-> K 't4'l dQ,^5,"-tl 3 tuA Lc{'s $+ el5e $,0,-. Ll15'l La.- '. a\" { Zshg Z. brt ^,- T L Sr,- z$o 3.1? xts u",.,. L.,tl. ) t d,tt*>: _I 'j.\ ltcc I fS r,rt' dclr*,.;e * thn l \c k*C t\ ce,P,l ttTc: #ots^): ol^rit1 KL.{.)t^ Ntr lvt )^/\ Qt.q ) (!.rr. xro'tr 1 l C b,olrx,ut!) 11S. o 1 2a. (2 points each) Circle the correct sign of work that would be associated with the following processes. HzO(g) - HzO(l) Volume of a gas sample decreases 4.0 L with Pext = 1 atm z PHa(B) + 3 Ot(g) -' PzOg(l) + 3 HzO(g) L mol of oxygen gas is compressed. A S = A S = w - - ' W = - 2b. (2 points each) Circle the correct sign of the entropy change that would be associated with the following processes. Chem IB midterm2 n^f Sa 6*r,^ 3a. (4 points) The diagram below contains the vapor pressure-temperature curve for methanol (CHgOH), with an external pressure of L atm. On this plot, sketch the vapor pressure-temperature curve for chloromethane (CHaCl) under these same experimental conditions. Explain your sketch in the space provided below the plot. Full credit will only be awarded for a correct explanation. 2 Pressure/ atm 1 ternp EXPLAIN: Methanol is an H-bonding m.olecule, znhereas CHsCI only has the dipote-dipole interaction. This results in CHICI hazting a lower normal boiling point than CHsOH, therefore I draut the ztapor pressure-temperature curoe for CHsCI reaching L atm pressure at a lower ozterqll temperature. 3b. (3 points) The heat of vaporization of methanol is 37.4 kJlmol. Would you expect the heat of vaporization for chloromethane to be 40.8 kJ/mol or 20.1 kJlmol? Explain your answer in the space below. No points awarded without an explanation. I expect the heat of aaporization for chloromethane to be 20.1 kfimoL The dominant IMF in CHSCI is the dipole-dipole force, whereas the dominant IMF in methanol is the H-bonding force. This tneans 1 mol of chloromethane should require less energy to aaporize, since weaker ozterall IMFs are being ooercome....
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This note was uploaded on 06/08/2008 for the course CHEM 1B taught by Professor King during the Spring '08 term at UC Irvine.

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Answers to midterm 2 - n^T fiL 6 v t CG,ttt^ 1(10 poinfs Platinum(symbol Pt has a density of 21 4 g cm-a It is observed that X-ray radiation of

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