2-12-2

English

Activity: Operating the Equipment

￿Reaction Path 1 Measurement

uTurn on the auto stirrer and start a measurement operation with the calculator.

uLittle-by-little, add sodium hydroxide (s) to the distilled water, and observe how the temperature changes.

uAfter all the sodium hydroxide (s) is dissolved and the temperature rise stabilizes, determine the heat of dissolution.

1 Beaker

4 Distilled Water

2 Temperature Probe

5 Temperature rise due

sto heat of dissolution

3 Sodium Hydroxide ( )

uTurn on the auto stirrer and start a measurement operation with the calculator.

uLittle-by-little, add the hydrochloric acid (aq) to the sodium hydroxide (aq), and observe how the temperature changes.

uAfter all the hydrochloric acid (aq) is added and the temperature rise stabilizes, determine the heat of neutralization.

uCalculate the sum of heat by adding the heat of neutralization to the heat of dissolution.

1 Beaker

4 Sodium Hydroxide (aq)

2 Temperature Probe

5 Temperature rise due

3 Hydrochloric Acid

to heat of neutralization

(aq)

 

 

 

￿Reaction Path 2 Measurement

uTurn on the auto stirrer and start a measurement operation with the calculator.

uLittle-by-little, add sodium hydroxide (s) to the hydrochloric acid (aq), and observe how the temperature changes.

uAfter all the sodium hydroxide (s) is dissolved and the temperature rise stabilizes, determine the heat of neutralization.

uCalculate the heat, and compare it with the total heat you calculated for Reaction Path 1.

1 Beaker

4 Hydrochloric Acid (aq)

2 Temperature Probe

5 Temperature rise due

3 Sodium Hydroxide

to heat of neutralization

(s)

 

 

 

When converting the temperature rise to joule heat, be sure to take the difference in the volume of water into consideration. The specific heat of distilled water is 4.2J/g°C.

Measurementasurement

￿Calculator Operation

uUse the Temperature Measurement Setup to measure the temperature and then display it.

uFind the applicable program in the Program Library (P.2-16-3), input it into your calculator, and then run it.

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uDetermine whether this activity verifies Hess’s Law. If it does not, consider the reason why.

uCompare the theoretical chemical reaction expression and the measurement results. If they do not match, consider the reason why.

uFind out if Hess’s Law holds true for other chemical reactions.

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