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InterviewSolution
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When a student mixed `50mL` of `1M HCI` and `150mL` of `1M NaOH` in a coffee cup calorimeter, the temperature of the resultant solution increases from `21^(@)C` to `27.5^(@)C`. Assuming that the calorimeter absorbs only a negligible quantity of heat, that the total volume of solution is `100mL`, its density `1gmL^(-1)` and that its specific heat is `4.18 J g^(-1)`. calculate: a. The heat change during mixing. b. The enthalpy change for the reaction `HCI(aq) +NaOH(aq) rarr NaCI(aq) +H_(2)O(aq)` |
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Answer» Number of moles of `HCI` and `NaOH` added `= (MV)/(1000) = (1xx150)/(1000) = 0.15` Miss of mixture `= V xx d = 1000 xx 1 = 100 g` Heat evolved, `q = ms DeltaT = 100 xx 4.18 xx (27.5 - 21.0)` `= 100 xx 4.18 xx 6.5J = 2717J = 2.717 kJ` The involved reaction is `HCI(aq) +NaOH(aq)rarr NaCI(aq) +H_(2)O` `DeltaH^(Theta) =` Heat evolved per mol `= (-2.717)/(0.15) =- 18.11 kJ` |
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