Download Thermochemistry - Heat of Neutralization PDF

TitleThermochemistry - Heat of Neutralization
File Size827.6 KB
Total Pages35
Document Text Contents
Page 1

HEAT OF
NEUTRALIZATION

Page 2

OBJECTIVESOBJECTIVES

 State what heat of neutralization isState what heat of neutralization is
D t i th h t f t li tiD t i th h t f t li ti Determine the heat of neutralizationDetermine the heat of neutralization

 Construct energy level diagrams for Construct energy level diagrams for
neutralization reactionsneutralization reactionsneutralization reactionsneutralization reactions

 Compare and explain the heat of Compare and explain the heat of
neutralization of a strong acid and a neutralization of a strong acid and a gg
strong alkali with the heat of strong alkali with the heat of
neutralization of weak acid and/or a weak neutralization of weak acid and/or a weak
alkalialkalialkalialkali

 Solve numerical problems related to the Solve numerical problems related to the
heat of neutralizationheat of neutralizationheat of neutralizationheat of neutralization

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Energy (kJ)

ΔH 54 6kJ

NaOH(aq) + CH3COOH(aq)

ΔH = - 54.6kJ

CH3COONa(aq) + H2O(l)

• The reaction between sodium hydroxide, NaOH and ethanoic acid, CH3COOH
to form sodium ethanoate, CH3COONa and water, H2O is exothermic.

• When one mole of sodium hydroxide, NaOH reacts with one mole of
ethanoic acid, CH3COOH to form one mole of sodium ethanoate, CH3COONa
and one mole of water, H2O, the quantity of heat released is 54.6kJ.

• The total energy of one mole of sodium hydroxide, NaOH and one mole of
ethanoic acid, CH3COOH is more than the total energy of one mole of sodium
ethanoate, CH3COONa and one mole of water, H2O. The difference in energy
is 54.6kJ.

• The temperature of the reaction mixture of sodium hydroxide, NaOH and
ethanoic, CH3COOH will rise.

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• Explanation
The heat given out (heat of neutralization) when a strong acid reacts with The heat given out (heat of neutralization) when a strong acid reacts with
strong alkali is higher than the heat given out when a weak acid reacts with
a strong alkali

 Ethanoic acid, CH3COOH is a weak acid, undergo partial ionization
i t t d h d i H+in water to produce hydrogen ions, H+.

 Some of ethanoic acid still remains molecule when dissolves in
water.water.

CH3COOH (aq) CH3COO- (aq) + H+ (aq)
 Some of heat given out during the neutralization is absorbed to

dissociate the acid completely in water.
 Thus, the heat of neutralization is always less than -57.3kJ.

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3. State two precautions that can increase the accuracy
of results in this experiment.p
(i) Mix the reactants quickly so that the reaction can be

completed faster.
(ii) The reading of the thermometer should be observed until(ii) The reading of the thermometer should be observed until

the highest temperature is recorded.

4. Why the heat of neutralization has a negative sign?
The reaction gives out heat that results in the increase of
temperature of the products formed.

Conclusion
Th h t f t li ti f id d lk li f diff tThe heat of neutralization for acids and alkalis of different
strengths are different.

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h dThe End

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