Calorimetry
The study of heat transfer during physical and chemical changes.
What is Calorimetry?
Using Hess’s Law, calculate the enthalpy change (ΔH°) for the following reaction:
A→C
Given the following equations:
A→B, ΔH = +50 kJ
B→C, ΔH = –30 kJ
What is the overall ΔH° for the reaction A → C?
What is +20 kJ?
This symbol represents the change in entropy in a chemical reaction.
What is Delta S?
What is the difference between an endothermic and exothermic reaction?
Endothermic means the species is gaining energy/ head and exothermic means the species is losing energy/heat.
The device used to measure heat changes in a reaction.
What is a calorimeter?
Hess’s Law allows the calculation of this value for a reaction when it cannot be measured directly by a lab.
What is the standard enthalpy change of a reaction (or ΔH°)?
If Delta S is positive, the disorder of a system does this.
What is increasing?
What is the fancy name for the process of going from a solid to a gas?
What is Sublimation?
The law stating that energy cannot be created or destroyed, only transferred.
What is the law of conservation of energy?
This term describes a reaction where the total enthalpy change is positive, indicating energy absorption.
What is an endothermic reaction?
This is what happens to the entropy of the system when water vapor condenses into liquid water at room temperature.
What is it decreases?
This phase change involves both an increase in entropy and an absorption of heat from the surroundings.
What is melting (or fusion)?
The formula used to calculate heat: q=mc∆T. What does each symbol represent?
What is heat (q), mass (m), specific heat capacity (c), and change in temperature (∆T)?
To apply Hess’s Law correctly, you must do this to the enthalpy change when a chemical equation is reversed.
What is change the sign of ΔH?
Delta G equals this expression.
What is Delta H minus T times Delta S?
(ΔG = ΔH - TΔS)
The equation for sublimation.
What is ΔHsub = ΔHfus + ΔHvap?
A 50.0 g piece of metal at 100.0 C is placed into a 100.0 g of water at 25.0 C in a perfectly insulated calorimeter. The final temperature of the system is 30.0 C. Assuming no heat is lost to the surroundings and the specific heat of water is 4.184 J/g C, calculate the specific heat capacity of the metal.
0.599 J/gC
Using Hess's Law, calculate the enthalpy change (ΔH°) for the combustion of methane:
CH4(𝑔) + 2O2(𝑔) → CO2(𝑔) + 2H2O(𝑙)
Given the following equations and their ΔH° values:
C(𝑠) + O2(𝑔) → CO2(𝑔), ΔH° = –393.5 kJ
H2(𝑔) + ½O2(𝑔) → H2O(𝑙), ΔH° = –285.8 kJ
C(𝑠) + 2H2(𝑔) → CH4(𝑔), ΔH° = –74.8 kJ
What is ΔH° for the combustion of methane?
What is -890.3 kJ/mol?
Among these three processes, this one has the greatest increase in entropy:
Dissolving NaCl in water
Boiling ethanol
Breaking a large protein into amino acids
What is breaking a large protein into amino acids?
Suppose you are camping and you get stuck in the frozen mountains. You are dehydrated but you have a stove and propane. You decided to drink the snow which is at -5 degrees celsius. Your body's internal temp is 37 degrees. To maintain your energy you need to heat the water up to a your body temp. How much KJ of energy do you need to make the snow safe to drink? (qtotal=qice + qfusion+qwater ΔHfus is 334 J/g)
What is 199.6 KJ?