06.03 Calorimetry: Lab Report
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Part I
The Dissolving of Solid Sodium Hydroxide in Water
Procedure:
1.
2.
3.
4.
Measure out approximately 200 mL of distilled water and pour it into the calorimeter. Stir
carefully with a thermometer until a constant temperature is reached. Record the volume of water
and the constant initial temperature of the water on your data table.
Place a plastic measuring trough on top of the digital balance, and then zero the balance (press the
tare button) so that the mass of the trough will be "ignored" and will not be added to the total mass
measured by the balance.
Measure out approximately three to five scoops of solid sodium hydroxide and record the mass to
your data table.
Place the solid sodium hydroxide into the water in the calorimeter and replace the lid immediately.
Stir gently until the solid is completely dissolved and record the highest temperature reached.
Data and Observations:
5.
Insert a complete data table, including appropriate significant figures and units, in the space
below. Also include any observations that you made over the course of Part I.
Volume of H2O
200.0 mL
H2O
Mass of NaOH
2.535 g NaOH
Initial temperature in
calorimeter
24.2 °C
Final temperature in calorimeter
27.8 °C
Calculations:
Show your work and write a short explanation with each calculation.
1.
Write out a balanced "equation" for the process you investigated in Part I, including phase
symbols.
NaOH(s) + H2O(l) --> NaOH(aq)
2.
Calculate the number of moles of sodium hydroxide dissolved. Show your work.
Moles NaOH = 2.535 grams NaOH X (1 mol/40.00 grams) = 0.06338 moles
NaOH
3.
Calculate the amount of energy involved in this dissolving process. Show your work.
q = m c (T2-T1)
200 mL H2O X 1 g/1 mL = 200 g H2O
c = 4.184 J/gC
T2 = 27.8 C
T1 = 24.2 C
Heat gained by H2O = 200 g X 4.18 J/gC X (27.8 - 24.2) = 3010 J
4.
4. Determine the enthalpy change, per mole of sodium hydroxide dissolved. Show your work.
3010 J / 0.06338 mol NaOH = 4.75X10^4 J/mole X 1 kJ/1000 J = 47.5 kJ/mol
NaOH
5.
The value determined in question 4 is the enthalpy change value you will need for Conclusion
question 1 below.
Part II
The Reaction of Sodium Hydroxide Solution with Hydrochloric Acid
Procedure:
1.
2.
3.
Measure out approximately 100 mL of 0.50 M hydrochloric acid solution and 100 mL of 0.50 M
sodium hydroxide solution. Record both volumes on your data table.
Pour the hydrochloric acid solution into the calorimeter. Measure and record the initial
temperature of each solution and record on your data table.
Add the sodium hydroxide solution to the acid solution in the calorimeter and immediately replace
the lid of the calorimeter. Stir the mixture and record the highest temperature reached.
Data and Observations:
4.
Insert a complete data table, including appropriate significant figures and units, in the space
below. Also include any observations that you made over the course of Part II.
Volume of HCl solution
100.5 mL HCl
Volume of NaOH solution
100.0 mL NaOH
Initial temperature in calorimeter
25.2 °C
Final temperature in calorimeter
28.2 °C
Calculations:
1.
Write out a balanced equation for the reaction you investigated in Part II, including phase
symbols.
HCl + NaOH → NaCl + H2O
2.
Determine the enthalpy change of this reaction. The mass of the sodium hydroxide and the mass of
the hydrochloric acid should be added together.
q = m × c × Δt
200.5 g of solution
200.5 g * 4.18*(28.2-25.2)= 2514.27 J
-2514.27/1000 = -2.514 kJ
= 1.258 kj/mol
3.
4.
5.
Determine the number of moles of NaOH.
Determine enthalpy per mole of NaOH. Show all of your work.
The value determined in question 4 is the enthalpy change value you will need for Conclusion
question 1 below.
Conclusion:
1.
Determine the enthalpy change for NaOH (s) + HCl (aq) → NaCl (aq) + H2O (l) using Hess's Law
-425.93 -92.30 -407.27 -285.83
Hess's Law: ΔH(rxn) = Sum[ΔH(f) products] - Sum[ΔH(f) reactants]
ΔH(rxn) = [(1 mol)(-407.27 kJ/mol) + (1 mol)(-285.83 kJ/mol)] - [(1 mol)(-425.93
kJ/mol) + (1 mol)(-92.30)]
= - 359.47 kj/mol
a. Write the balanced chemical reaction and enthalpy change for Part I (1pt)
b. Write the balanced chemical reaction and enthalpy change for Part II (1pt)
c. Calculate the enthalpy change using Hess's Law. Refer to the lesson for an example of Hess's
Law. (2pt)
2.
If the accepted enthalpy change value for the dissolving of sodium hydroxide in water is −44.2
kilojoules per mole, determine the percent error of the experimental value that you calculated in
Part I. Show your work.
(experimental - actual value) / actual value × 100 %
3.
If the accepted heat of reaction for the neutralization of hydrochloric acid with sodium hydroxide
is −56.0 kilojoules per mole, determine the percent error of the experimental value that you
calculated in Part II. Show your work.
(experimental - actual value) / actual value × 100 %
4.
Using the accepted values of the processes you've examined, would your estimation of the
enthalpy change for the reaction of solid sodium hydroxide in aqueous hydrochloric acid change
from the prediction you made in question one? Explain your answer in complete sentences.
5.
Give a detailed explanation, using what you know about bonds and forces of attraction, for the
enthalpy changes you observed in parts I and II of this lab. Explain your answer in complete
sentences.
6.
If the hole for the thermometer in a calorimeter is wider than the diameter of the thermometer,
leaving a gap between the lid and the thermometer itself, how do you think this would this affect
the temperature change observed in the experiment? How would this affect the calculated enthalpy
change? Explain your answers in detail.