Question

• 50.5 kJ of heat is released when 1 mole of HCl reacts with 1 mole of NaOH to produce 1 mole of NaCl and 1 mole of H2O. Write a thermochemical equation for this reaction.

•The equation below shows that dissolving 1 mole of NaOH in water releases 40.05 kJ of heat (q). What if there was 2 moles of NaOH, how much heat would be released (q)?

NaOH(s) ​​​​Na+(aq)​+​OH-(aq)​​+​40.05 kJ

• From the equation above, calculate the amount of NaOH that needs to be dissolved (in moles) in order to release 1000 kJ of heat (q).

• What should happen to the temperature of the solution produced from dissolving NaOH(s) in distilled water?

• Write the following sentence as a chemical equation:

“When 1 mole of HCl(aq) neutralizes 1 mole of NaOH(aq), 100.1 kJ is released”

Answer 1

Answer 1.

Molecular Reaction: NaOH_(s) + HCl_(aq) -------> NaCl_(aq) + H₂O_(l), dH = - 50.5 kJ

Net ionic Reaction: NaOH_(s) + H⁺_(aq) ---------> Na⁺_(aq) + H₂O_(l), dH = - 50.5 kJ

Answer 2. Usually enthalpy change double when the number of moles of reactants is doubled. Hence, 80.1 kJ heat will be release when 2 moles of NaOH is used.

Answer 3. Since, 40.05 kJ heat release when 1 mole of NaOH is used.

Than, 1000 kJ heat release when X mole of NaOH is used.

X = 1000 x 1/40.05

X = 25 mole of NaOH

Answer 4. The temperature of the solution will increase when NaOH is dissolved in distilled water to make the solution

Answer 5.

Chemical Equation: NaOH_(s) + HCl_(aq) -------> NaCl_(aq) + H₂O_(l), dH = - 100.1 kJ