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Chemistry Students: Hess's Law Lab

This document describes an experiment to calculate the heat of formation of magnesium oxide (MgO) using Hess's law and a thermochemical cycle. The experiment involves measuring temperature changes for chemical reactions involving magnesium and magnesium oxide. Using the measured temperature changes and heat calculation formulas, the heat released or absorbed by each reaction can be determined. Hess's law is then applied to calculate the heat of formation of MgO from the heats of reaction. The calculated value is compared to the accepted literature value to evaluate the accuracy of the experiment.

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Prity Pramanik
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20 views2 pages

Chemistry Students: Hess's Law Lab

This document describes an experiment to calculate the heat of formation of magnesium oxide (MgO) using Hess's law and a thermochemical cycle. The experiment involves measuring temperature changes for chemical reactions involving magnesium and magnesium oxide. Using the measured temperature changes and heat calculation formulas, the heat released or absorbed by each reaction can be determined. Hess's law is then applied to calculate the heat of formation of MgO from the heats of reaction. The calculated value is compared to the accepted literature value to evaluate the accuracy of the experiment.

Uploaded by

Prity Pramanik
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Reactivity 1: What drives chemical reactions?

R.1.2 Energy cycles in reactions

R.1.2.2 Hess's law

Objective Investigation Tools used Process


Apply Hess’s law Thermochemical Experimental Tools: Inquiry 1: Exploring and
to calculate Cycle for the • Weighing Scale Designing
enthalpy changes Formation of • Styrofoam Cup How can we determine the
in multistep Magnesium or Calorimeter heat of formation of
reactions. Oxide • Thermometer/ magnesium oxide (MgO) using
temperature a thermochemical cycle and
sensor Hess's Law?
• Reactants that Hypothesis: The heat of
provide the formation of magnesium oxide
necessary can be calculated by using
chemical known reactions and applying
reactions. Hess's Law.
• Safety Background: Explain the
Equipment principles of Hess's Law,
thermochemical cycles, and the
significance of heat of
Technological and formation.
Experimental Design: Outline
mathematical tools
the plan for using magnesium
• Graphing ribbon, magnesium oxide
powder, and acids. Describe the
calculator reactions and the reasoning
behind the chosen reactions.
Variables: Identify the
independent (reactants),
dependent (temperature
change), and controlled
variables.
Procedure: Provide step-by-
step instructions for the
experiment setup, including
reaction mixtures and
measurements.
Inquiry 2: Collecting and
Processing

Data Collection: Record the


initial and maximum
temperatures for each reaction
involving magnesium and
magnesium oxide.
Reaction 1: Mg + HCl
Initial Temperature: [Value] °C
Maximum Temperature: [Value]
°C
Calculations: Calculate the
temperature change (ΔT) for
each reaction by subtracting
the initial temperature from
the maximum temperature.
Heat Calculations: Use the
formula q = m × c × ΔT to
calculate the heat transferred
(q) for each reaction, where m
is mass and c is specific heat
capacity.
Inquiry 3: Concluding and
Evaluating
Results: Present the calculated
values of heat transferred (q)
for each reaction.
Hess's Law Application: Show
how Hess's Law is applied to
calculate the heat of formation
of magnesium oxide (MgO)
using the calculated heats of
reaction.
Comparison to Literature
Value: Compare the calculated
heat of formation with the
accepted literature value.
Discuss any discrepancies and
possible sources of error.
Conclusion: Summarize the
findings and their significance.
Discuss the success of the
experiment in achieving the
research question's goal.
Evaluation: Reflect on the
experiment's strengths and
limitations. Consider
improvements that could
enhance the accuracy and
reliability of the results

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