2. A I litter sample of 10.00 M NaOH is mixed with 99 mL of 2.00 M H.So, in a la

Question

2. A I litter sample of 10.00 M NaOH is mixed with 99 mL of 2.00 M H.So, in a large Styrofoam coffee cup; the cup is fitted with a lid through which passes a calibrated thermometer The temperature of each solution before mixing is 21.85°C. After adding the NaOH solution to the coffee eup and stirring the mixed solutions with the thermometer, the maximum temperature measured is 32.90 . Assume that the density of the mixed solutions is 1.00 gmL, that the specific heat of the mixed solutions is 4.18 J/(gc), and that no heat is lost to the surroundings Calculate the enthalpy change per mole of H2SOs in the reaction

Explanation / Answer

Total volume = 1000 ml + 99 ml = 1099 ml

density = 1.00 g/ml

So,

mass of solution (m) = 1099 ml x 1 g/ml = 1099 g

change in temperature after mixing (dT) = 32.90 - 21.85 = 11.05 oC

Cp = 4.18 J/g.oC

Using,

enthalpy (dH) = -heat (q) = -mCpdT

= -1099 x 4.18 x 11.05/1000

= -50.762 kJ

moles of H2SO4 = 2.00 M x 0.099 L = 0.198 mol

So,

dH/mole H2SO4 = -50.762 kJ/0.198 mol = -256.374 kJ/mol        

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