molecular chemistry

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0 [{"id":463144,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:01:57","updated_at":"2018-05-15 10:24:49","questionName":" State the two postulates of statistical thermodynamics.\r\n(b) What is the significance of the canonical partition function?\r\n","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":20,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463149,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:03:33","updated_at":"2018-05-15 10:24:49","questionName":"Sketch the contour plot of the potential energy surface of a reaction with an early\r\nbarrier to reaction. What effect does the position of the barrier have on the vibrational\r\ndistribution of the products?","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":25,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463133,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 09:57:46","updated_at":"2018-05-15 10:24:49","questionName":"The CO molecules are confined in a vessel of volume V=100 cm3\r\n.\r\n(i) Calculate the translational partition function qtrans =V \/ \u039b3 for one CO\r\nmolecule at 298K. The de Broglie wavelength is given by\r\n\u039b = h2 \/(2\u03c0mkBT) . (4 marks)\r\n(ii) What is the condition for using the approximate expression above for the\r\ncalculation of qtrans and is this condition fulfilled? ","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":16,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463140,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:00:10","updated_at":"2018-05-15 10:24:49","questionName":"Sketch and label a contour plot for the potential energy surface for this\r\nreaction paying particular attention to the location of the transition state. On\r\nyour sketch include a trajectory leading to a vibrationally excited product.\r\nProvide a brief explanation of why such a high fraction of the reaction\r\nexothermicity appears as vibration.","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":19,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463145,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:02:16","updated_at":"2018-05-15 10:24:49","questionName":"Consider an isolated system of 3 distinguishable, non-interacting, atoms that occupy a\r\nset of 4 energy levels which are equally spaced by one energy unit \uf065. Assume that the\r\nground state has energy zero. How many microstates are compatible with the\r\nmacrostate if the total energy of the system is 3\uf065 ?","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":21,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463148,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:03:17","updated_at":"2018-05-15 10:24:49","questionName":"Sketch the minimum potential energy diagram for a barrierless recombination reaction\r\nsuch as CCl3 + CCl3 \u2192 C2Cl6. Show the approximate location of the transition state\r\nand explain why there is a minimum in the number of rovibrational states at this point.","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":24,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463132,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 09:57:16","updated_at":"2018-05-15 10:24:49","questionName":" In general, what does the magnitude of the molecular partition function indicate\r\nabout the ability of CO molecules to store energy and how that energy is distributed\r\nover the molecular energy levels?","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":15,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463152,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:04:06","updated_at":"2018-05-15 10:24:49","questionName":"The cross section for the D2 + C2D4 collision is 4.6 \u00d7 10-19 m\r\n2\r\n.Calculate the collision\r\ntheory pre-exponential factor for the reaction of D2 + C2D4 at 900 K. Would you\r\nexpect your answer to be bigger or smaller that the observed pre-exponential factor?","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":26,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463136,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 09:59:26","updated_at":"2018-05-15 10:24:49","questionName":"Outline a technique by which you could study the rotational and vibrational\r\ndistribution of the products formed in a gas-phase chemical reaction. Include a\r\nlabelled diagram of the apparatus. What are the advantages and disadvantages of your\r\nchosen technique?","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":18,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463159,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:05:13","updated_at":"2018-05-15 10:24:49","questionName":" List the assumptions made in deriving the Langmuir Isotherm (\r\nbp\r\nbp\r\n\uf02b\r\n\uf03d\r\n1\r\n\uf071 ) for the\r\nabsorption of gases on to a surface. Briefly comment on the validity of these\r\nassumptions. What would you measure and plot in order to determine the volume\r\nadsorbed at a monolayer coverage?","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":28,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463134,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 09:58:41","updated_at":"2018-05-15 10:24:49","questionName":" use qvib = T \/\u03b8vib to obtain an expression for the vibrational contribution to\r\nthe internal energy of CO as a function of T and hence the vibrational\r\ncontribution to the molar heat capacity CV.\r\n(ii) explain why this result is expected from the equipartition theorem? ","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":17,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463156,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:04:52","updated_at":"2018-05-15 10:24:49","questionName":"Briefly outline the assumptions behind the Eyring equation (k = k\u2260K\u2260) and show how it can be derived by considering an equilibrium between reagents and the\r\ntransition state.","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":27,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463147,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:02:56","updated_at":"2018-05-15 10:24:49","questionName":"Comparison of theoretical calculations and experimental measurements of the entropy\r\nof matter can differ quite substantially, a fact that is attributed to residual entropy.\r\n(a) Explain the origin of residual entropy?\r\n(b) Give a quantitative estimate of the magnitude of residual entropy.","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":23,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463160,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:05:32","updated_at":"2018-05-15 10:24:49","questionName":"Compare and contrast the mechanisms of a bimolecular reaction occurring in the\r\ngas phase and via a Langmuir mechanism. Derive the following expression for the\r\nratio of transition state theory rate coefficients for heterogeneous (khet) and\r\nhomogeneous (khom) rate coefficients:\r\nwhere [-S-S-] is the surface concentration of adjacent vacant sites, q\r\n\u2260\r\nis the partition\r\nfunction for the appropriate transition state and \u2206E is the difference in activation\r\nenergies of the homogeneous and heterogeneous reactions. Explain why the difference\r\nin activation energies needs to be large for this ratio to be >1.\r\n","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":29,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null},{"id":463146,"quiz_id":"23778","answer_id":null,"answerType_id":"0","created_at":"2018-05-15 10:02:35","updated_at":"2018-05-15 10:24:49","questionName":"Statistical thermodynamics provides an interpretation of the heat capacity in terms of\r\nenergy levels.\r\n(a) What does a constant, non-zero, heat capacity indicate?\r\n(b) What does a jump in the heat capacity indicate?","questionTimeSeconds":"0","questionTimeMinutes":"10","questionImagePath":null,"position":22,"explanation":"","question_score_id":null,"lang":"","questionAudioPath":null}]
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State the two postulates of statistical thermodynamics. (b) What is the significance of the canonical partition function?

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