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 `1gm-mL^(-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)`

When a student mixed `50mL` of `1M HCI` and `150mL` of `1M NaOH` in a

1.	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 `1gm-mL^(-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)`
Answer» (a). Number of moles of HCl and NaOH added `=(MV)/(1000)=(1xx50)/(1000)=0.05` Mass of mixture `=Vxxd=100xx1=100g` Heat evolved, `q=msDeltaT=100xx4.18xx(27.5-21.0)` `=100xx4.18xx6.5J=2717J=2.717kJ` (b). The involved reaction is: `HCl(aq.)+NaOH(aq.)toNaCl(aq.)+H_(2)O` `DeltaH=`Heat evolved per mol `=(-2.717)/(0.05)=-54.34kJ`

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