// Numbas version: finer_feedback_settings
{"name": "Chemical Thermodynamics: Enthalpy Change and Vaporisation", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"name": "Chemical Thermodynamics: Enthalpy Change and Vaporisation", "tags": [], "metadata": {"description": "<p>Public</p>", "licence": "Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International"}, "statement": "", "advice": "<p>Mathematically, the definition of entropy is:</p>\n<p></p>\n<p>$\\mathrm{dS=\\frac{dQ}{T}}$,&nbsp;</p>\n<p></p>\n<p>where $\\mathrm{dS}$ is an infinitesimal entropy change; $\\mathrm{dQ}$ is an infinitesimal heat transfer to the system being described (i.e. it has negative value if heat is removed from the system); and $\\mathrm{T}$ is the temperature of the system, in $\\mathrm{K}$.</p>\n<p></p>\n<p>This equation works because the temperature of the system effectively remains constant during an infinitesimal heat transfer, whereas it generally does<strong> not</strong> work for any macroscopic heat transfer, as the temperature will change due to the heat transfer (the equation would effectively change as we added heat) - <strong>however</strong>, if the system is undergoing a phase change then its temperature will remain <strong>effectively constant</strong>, as the heat energy is being used to promote particles to the new phase instead of to increase their temperature.&nbsp;This allows us to integrate the formula whilst treating $\\mathrm{T}$ as a constant:</p>\n<p>$\\mathrm{\\Delta S=\\int dS=\\int \\frac{dQ}{T}=\\frac{\\Delta Q}{T}}$ .</p>\n<p></p>\n<p>Even if you don't remember that explanation, it's important to remember that <strong>if</strong> a system is undergoing a phase change, then the entropy change corresponding to a given heat transfer to the system is given by:</p>\n<p>$\\mathrm{\\Delta S=\\frac{\\Delta Q}{T}}$ .</p>\n<p></p>\n<p>Additionally, if the heat supplied to the system is the total enthalpy change for that phase change, e.g. the enthalpy of vaporisation, then we will use that value in place of $\\mathrm{\\Delta Q}$:</p>\n<p>$\\mathrm{\\Delta S=\\frac{{\\Delta H}_{vap}}{T}}$ .</p>\n<p></p>\n<p>We are given the entropy change for the vaporisation of chloroform, $\\mathrm{{\\Delta S}_{vap}=\\var{sigformat(entro,5)}\\space J\\space K^{-1}\\space mol^{-1}}$, at a temparature of $\\mathrm{\\var{ktemp} \\space K}$, and asked to calculate the corresponding enthalpy change.&nbsp;</p>\n<p></p>\n<p>To do this, we will rearrange our established equation, then simply substitute in the values we have been provided:</p>\n<p>$\\mathrm{{\\Delta S}_{vap}=\\frac{{\\Delta H}_{vap}}{T}}$</p>\n<p></p>\n<p>$\\mathrm{\\Rightarrow\\space\\space\\space {\\Delta H}_{vap}=T{\\Delta S}_{vap}}$</p>\n<p></p>\n<p>$\\mathrm{\\Rightarrow\\space\\space\\space {\\Delta H}_{vap}=\\var{ktemp}\\times \\var{sigformat(entro,5)}=\\var{sigformat(trueheat,3)}\\space J\\space mol^{-1}}$ .</p>\n<p></p>\n<p>To quote our answer in the units asked for, we divide by one thousand to obtain:</p>\n<p>$\\mathrm{{\\Delta H}_{vap} = \\var{sigformat(heat,3)}\\space kJ\\space mol^{-1}}$ .</p>", "rulesets": {}, "extensions": [], "builtin_constants": {"e": true, "pi,\u03c0": true, "i": true, "j": false}, "constants": [], "variables": {"entro": {"name": "entro", "group": "Ungrouped variables", "definition": "trueheat/ktemp", "description": "", "templateType": "anything", "can_override": false}, "trueheat": {"name": "trueheat", "group": "Ungrouped variables", "definition": "heat*1000", "description": "", "templateType": "anything", "can_override": false}, "ktemp": {"name": "ktemp", "group": "Ungrouped variables", "definition": "334.88", "description": "", "templateType": "anything", "can_override": false}, "heat": {"name": "heat", "group": "Ungrouped variables", "definition": "random(11 .. 75#0.1)", "description": "", "templateType": "randrange", "can_override": false}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": ["entro", "trueheat", "ktemp", "heat"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>Complete the following description of enthalpy change:</p>\n<p>The enthalpy change of a system is equal to the amount of [[1]] between the system and [[2]] during a process that occurs at [[3]] pressure, if no other [[4]] occurs other than that due to expansion of the system.</p>\n<p></p>\n<p></p>\n<p></p>\n<p></p>\n<p>The entropy of vaporisation of chloroform is found to be $\\mathrm{\\var{sigformat(entro,5)}\\space J\\space K^{-1}\\space mol^{-1}}$ at its normal boiling point of $\\mathrm{\\var{ktemp}\\space K}$. Calculate the latent heat of vaporisation of chloroform at this temperature, in $\\mathrm{kJ\\space mol^{-1}}$ .</p>\n<p></p>\n<p>[[0]] $\\mathrm{kJ\\space mol^{-1}}$ .</p>", "gaps": [{"type": "numberentry", "useCustomName": false, "customName": "", "marks": "2", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "heat-(heat/200)", "maxValue": "heat+(heat/200)", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "displayAnswer": "", "precisionType": "sigfig", "precision": "3", "precisionPartialCredit": "50", "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": true, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en", "scientific"], "correctAnswerStyle": "plain"}, {"type": "1_n_2", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["heat transferred", "entropy gained", "work done"], "matrix": ["1", 0, 0], "distractors": ["", "", ""]}, {"type": "1_n_2", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["the surroundings", "its molecules", "its container"], "matrix": ["1", 0, 0], "distractors": ["", "", ""]}, {"type": "1_n_2", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["constant", "high", "low"], "matrix": ["1", 0, 0], "distractors": ["", "", ""]}, {"type": "1_n_2", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["work", "entropy change", "enthalpy change"], "matrix": ["1", 0, 0], "distractors": ["", "", ""]}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always", "contributors": [{"name": "Frances Docherty", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/4059/"}, {"name": "Michael McFadden", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/18132/"}], "resources": []}]}], "contributors": [{"name": "Frances Docherty", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/4059/"}, {"name": "Michael McFadden", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/18132/"}]}