The molar heat of a solution, ʌH soln , of NaOH is -44.51 kJ/mol . In a certain experiment, 36.5 grams of NaOH is completely dissolved in 100 mL of water at 22.0° C in a foam cup calorimeter. Calculate the final temperature of the water.
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Expert's answer
2017-05-27T04:18:10-0400
The enthalpy change of solution is the enthalpy change when 1 mole of an ionic substance dissolves in sufficient water to give a solution of infinite dilution. In our task we have 36.5 g NaOH and we should calculate the quantity in moles: n(NaOH)= m (NaOH)M(NaOH)= 36.540=0.9125 (mol) We know that 44.51 kJ are evolved from 1 mol NaOH, but we have 0.9125 mol. So the calculation of heat will be next: Q=-∆H1=∆H×n(NaOH)1 mol= -44.51×0.91251=40.62 (kJ) From equitation we know that: Q=c×m×(T2-T1)⇒T2=Qc×m+T1 c – heat capacity of water, m – mass of water T2=40.62*10004.1813×100+(273+22)=392.1 K= 119.1℃ Answer: 119.1°C.
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