Terms
What is a system?
The part of the universe we focus on for any reaction
What is Ideal Gas Law?
PV = nRT
What is Δ E?
The change in a system's internal energy,
E(final) - E (initial)
E(products) - E(reactants)
If P is constant, why should we use enthalpy (H)?
Eliminates the need to measure PV work. I relates directly to energy changes at constant pressure
What is C and c? (case is important!)
C=heat capacity (amount of heat required to change substance by 1 K)
c = specific heat capacity (amount of heat required to change the heat of 1 g by 1 K)
What is a Joule? What is a calorie? Which is the standard unit?
1 J = 1 kgm2/s2
1 cal = quantity of energy needed to raise the T of 1 g of water by 1 oC
Joule is the SI unit (1 cal = 4.184J)
The ideal gas law is the combination of what three simple gas laws?
Boyle's, Charles's, and Avogadro's
Say that the system both releases heat and does work on its surroundings. What is Δ E?
heat released (-q) and work done (-w) will always mean energy released ( - Δ E)
What do you call a reaction that releases heat?
Exothermic
How is specific heat capacity (c) found for any substance?
Experimentally
What is pressure according to Kinetic Molecular Theory?
The force of particle collisions with the wall of a container.
What is the density of one mole of sulfur dioxide gas in a closed container at a constant temperature of 50 oC and pressure of 520 torr?
D = 1.65 g/L
What is the first law of thermodynamics?
Both enthalpy and internal energy are state functions. What is a state function?
It is a function defined for a system relating several state variables or state quantities that depends only on the current equilibrium state of the system.
(Doesn't take into account any equilibrium of the reaction or the physical state)
What are the two major types of calorimetry?
Constant-Pressure(coffee cup) and Constant-Volume(bomb)
What is a Joule? What is a calorie? Which is the standard unit?
1 J = 1 kgm2/s2
1 cal = quantity of energy needed to raise the T of 1 g of water by 1 oC
Joule is the SI unit (1 cal = 4.184J)
What is R?
Universal gas constant. When used in the ideal gas law, R = 0.0821 atmL/molK
What is Hess's Law?
the enthalpy change for an overall process is the sum of the enthaply changes of all individual steps
What are the 3 cases in which enthaply can be used over internal energy?
1. Reactions that do not involve gases (Δ V is negligible)
2. Reactions in which the amount of gas does not change (constant V)
3. Reactions in which the amount of gas does change (qp is much larger than PΔ V, so difference between Δ H and Δ E is negligible)
Cal is quantity of energy needed to raise 1 g of water by 1 oC and Btu is the quantity needed to raise the temperature of 1 lb of water by 1 oF. How many J is 1 Btu?
(1 cal = 4.184 J, 1 lb = 454g)
1 Btu = 1.1 x 103 J
What is R in a root-mean-squared function?
R = 8.314 J/molK
A steel tank has a volume of 438L and is filled with 0.885 kg of pure oxygen gas. Calculate the pressure of the gas at 21oC
P = 1.53 atm
find q when 22.0g of water is heated from 25oC to 100oC
q = 6.9 x 103 J
Explain the enthalpy of freezing water. (Bonus points if enthalpy chart is included)
Freezing water releases heat, is exothermic, and therefore has -Δ H
2.5 g of C2H2 is burned in a bomb calorimeter with a heat capacity of 10.85kJ/K, and the temperatrue increased from 23.488oC to 34.988oC. What is Δ E (in kJ/mol)?
Δ E = -1.30 x 103 kJ/mol of C2H2