Question

3.An aqueous solution of Na3PO4 is heated from 24.7o C to 35.6o C. How much heat was absorbed by the solution?

1. Consider the chemical equation below. Is the reaction endothermic or exothermic? Explain your answer. HCl(aq) + NaOH(aq) J NaCl(aq) + H2O(l) -56.13 kJ

2. In the reaction in question 1, how many kJ of energy are produced when 0.041 moles of HCl are neutralized by an excess of NaOH?

Answer 1

(3) The amount of heat absorbed by the solution , Q = mcdt

Where

m = mass of the solution =

c = specific heat capacity of Na3PO4 solution = 4.057 J/g-oC

dt = change in temperature = final - initial = 35.6 - 24.7 = 10.9 oC

If we know the mass of the solution we have to fing the amount of the solution.

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(1) HCl(aq) + NaOH(aq) NaCl(aq) + H₂O(l) H = -56.13 kJ

Here the change in enthalpy is -ve that means heat is released so the reaction is exothermic reaction.

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(2) From the above balanced reaction ,

1 mole of HCl reacts with excess NaOH produces 56.13 kJ of heat

0.041 mole of HCl reacts with excess NaOH produces M kJ of heat

M = ( 0.041 x 56.13) / 1

   = 2.30 kJ

Therefore the amount of energy produced is 2.30 kJ