Temperature
Heat
State Changes
Chemical Changes
Hess's Law
100
What is temperature?
The average kinetic energy of a substance
100
How does heat transfer?
Through molecular collisions. That's why hydroflasks work so well: vacuum seal meaning not many molecules to transfer heat!
100
What state change is happening at IV on the graph?
Boiling or vaporizing
100
If energy is released during a reaction, is that endothermic or exothermic?
exothermic
100
What do the values of ΔH (positive and negative) mean for a reaction?
positive is energy released (exothermic), negative is energy absorbed (endothermic)
200
What is the temperature in ºC of a room that is 72ºF?
22ºC
200
What is the specific heat of a 30.0 g substance that absorbed 3000. J of heat while heating from 12.0ºC to 35.0 ºC?
4.35 J/gºC
200
Without changing temperature, how can a liquid turn into a gas (vaporize)?
by decreasing pressure
200
If the reactants of a chemical reaction have less energy than the products, do the surroundings gain or lose energy?
Surroundings lose energy
200
How did we apply Hess's Law in our lab?
We were able to find the Enthalpy of Reaction for the combustion of magnesium by doing a series of reactions.
300
What happens at absolute zero (0 Kelvin)?
Molecules don't move
300
if a cup of coffee cools down and releases 300 J of heat into the air around it. How much energy does the air absorb?
300 J
300
What were we finding when we completed the lab where we melted ice?
The heat of fusion of ice
300
How do the total bond energies of the reactants compare to that of the products when energy is released during a reaction?
The total bond energies of reactants is more than the total bond energies of products when energy is released during a reaction.
300
Find the enthalpy of the following reaction.
2NOCl(g) → 2NO(g) + Cl2(g)
Given the following known enthalpies:
2NO(g) → N2(g) + O2(g) ΔH = −180.6 kJ
N2(g) + O2(g) + Cl2(g) → 2NOCl(g) ΔH = +103.4 kJ
77.2 kJ
400
What is the difference between temperature and heat?
Temperature is the average KE, Heat is the change in thermal energy (total KE)
400
You are trying to determine the specific heat of an unknown liquid. You heat a steel block that has a mass of 13.1 g to 97.2 °C. The steel block is placed into an insulated flask containing 56.2 g of the unknown liquid at 23.2 °C. The final solution temperature stabilizes at 35.1 °C. If the specific heat of steel is 0.470 J/g⋅°C, what is the specific heat of the liquid?
0.572 J/gºC
400
how much energy is required for 45.6 g of water to evaporate?
Hvap = 2.260 kJ/g
103 kJ
400
The ΔH of a reaction is 113 kJ/mol. What type of reaction is this?
Exothermic
400
Use the two reactions below to find the enthalpy for the total reaction:
Pb + PbO2 + 2H2SO4 → 2PbSO4 + 2H2O
Using the following two reactions:
(1) Pb + PbO2 + 2SO3 → 2PbSO4 ΔH° = −775 kJ
(2) SO3 + H2O → H2SO4 ΔH° = −113 kJ
-549 kJ
500
A block of gold is 47ºF, what is the temperature in Kelvin?
280 K
500
An insulated flask contains 432 g of water at 18.4 °C and a second beaker contains 64.9 g of water at 97.7 °C. What is the final temperature of the water after the hot water is poured into the insulated flask? (The specific heat of water is 4.184 J/g⋅°C)
28.8ºC
500
How much energy is released when 50.6 g of ice freezes?
Hfus = 6.01 kJ/mol
16.9 kJ
500
Does a longer or shorter bond take more energy to break?
A shorter bond (double, triple bonds) takes more energy to break than a longer (single) bond.
500
Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
H2SO4(l) → SO3(g) + H2O(g)
H2S(g) + 2 O2(g) → H2SO4(l) ΔH = –235.5 kJ
H2S(g) + 2 O2(g) → SO3(g) + H2O(l) ΔH = –207 kJ
H2O(l) → H2O(g) ΔH = 44 kJ
73 kJ