Thermochemistry
What is temperature a measure of?
The average kinetic energy of the particles
What is specific heat capacity a measure of?
The amount of ENERGY to raise 1 GRAM of a substance by 1 DEGREE CELCIUS. (J/g°C)
What is calorimetry used for?
Calorimetry is used to measure the amount of heat transferred in chemical or physical processes.
What does STP stand for?
Standard Temperature (0C / 273 K) and Pressure (0 atm)
What does R mean in the ideal gas law equation PV=nRT?
It is a constant (the universal gas constant). It's value is 0.08206 Lxatm/molxK
What is heat?
Aluminum has a specific heat of 0.903 J/g°C. Copper has a specific heat of 0.385 J/g°C. If I have 1 gram of each and apply 20 joules of heat to each, which will change temperature the most? Explain why.
Copper because it has a lower specific heat value meaning it takes less energy to raise one gram by one degree.
1st Law: Energy cannot be created or destroyed. It can only change forms or be transferred from one object to another.
At the start of every gas law problem, what is the first thing you should do?
You should check to see if your temperatures are in Kelvin, and if not, you should convert them to Kelvin.
A container with a movable piston has 1.20 moles of oxygen gas at a volume of 24.0 L. If 0.60 moles of gas are added to the container while keeping temperature and pressure constant, what is the new volume?
36.0 L
Which of the following is NOT true for endothermic reactions?
a. The energy of the products is higher than the energy of the reactant
b. Heat is found in the reactants
c. ΔH is negative
d. The reactant feels cold to the touch.
c. ΔH is negative
5.0 g of copper was heated from 20.0°C to 80.0°C. How much energy was used to heat Cu? (Specific heat capacity of Cu is 0.385 J/g°C) (your answer must have the correct number of sig figs!)
120 J
A sample of a metal with a mass of 30 g was heated to 175°C. It was then quickly moved to an insulated container holding 30 g of water at 0°C. The final temperature of both the metal and the water was 50°C. Which of the following can be concluded?
a. The metal temperature changed more than the water temperature did; therefore, the heat capacity of the metal must be less than the heat capacity of the water.
b. The metal temperature changed more than the water temperature did; therefore, the heat capacity of the metal must be more than the heat capacity of the water.
c. The metal temperature changed more than the water temperature did; therefore, the metal lost more thermal energy than the water gained.
d. The metal temperature changed more than the water temperature did; therefore, the water lost more thermal energy than the metal gained.
a. The metal temperature changed more than the water temperature did; therefore, the heat capacity of the metal must be less than the heat capacity of the water.
A balloon of volume V is placed in a refrigerator. What will happen to its volume?
Since the temperature decreases, the volume will also decrease. The lower temperature causes the gas to have a lower average kinetic energy, meaning the particles will move less and take up less space.
A given mass of gas in a rigid container is heated from 100 °C to 300 °C. By what factor will the pressure increase or decrease?
increase by a factor of about 1.5
Describe why the temperature does NOT increase during a phase change.
All of the energy is going towards breaking the intermolecular forces instead of increasing the kinetic energy.
If a 3.10 g ring is heated using 40.2 joules, its temperature rises 17.9°C. Calculate the specific heat capacity of the ring.
0.724 J/g°C
Calculate the specific heat of a metal if a 55.0g sample of an unknown metal at 99.0°C is added to 225.0 g of water at 22.0°C and raises it to 23.2°C. (The specific heat of water is 4.184 J/g°C.)
0.271 J/g°C
Name one of the postulates of the Kinetic Molecular Theory of gases.
1. The particles in a gas are in constant, random motion.
2. The combined volume of the particles is negligible.
3. The particles exert no forces on one another.
4. Any collisions between the particles are completely elastic (don't lose energy).
5. The average kinetic energy of the particles is proportional to the temperature in Kelvins
A mixture of 90.0 grams of CH4 and 10.0 grams of argon has a pressure of 250 torr under conditions of constant temperature and volume. What is the partial pressure of CH4 in torr? (CH4=16.04 g/mol, Ar = 39.948 g/mol)
239 torr
Draw an endothermic reaction graph. Be sure to label the axes, reactants, products, and energy change (ΔH)
(i have to pay for jeopardy to insert an image :()
400 g of water at 22°C was heated with 6384 J of thermal energy. Calculate the final temperature of the water. (Water's specific heat capacity is 4.184 J/g°C)
26°C
A 125 g sample of water was heated to 100.0°C and then a bar of platinum at 20.0°C was dropped into the beaker. The temperature of the platinum in the beaker quickly rose to 35.0°C. The specific heat of platinum is 0.133 J/g°C. The specific heat of water it 4.184 J/g°C. What is the mass of the platinum bar? (You must have the correct number of sig figs!)
17,000 g Pt = 1.70 x 104 g Pt
What is the total volume of products formed at STP when 1.2 g of carbon is burned? (STP = 0 °C & 1 atm)
2.2 L
A container with volume 71.9 mL contains water vapor at a pressure of 10.4 atm and a temperature of 465oC. How many grams of the gas are in the container?
0.222 grams