joule Explanation: The SI unit of energy is the joule (J), which is defined as the amount of energy needed to apply a force of one newton over a distance of one meter.
question
List some other common units of energy.
Check all that apply.
answer
kilowatt-hour
calorie Explanation: Some other common units of energy include:-Joules-Kilojoules-Calories-Kilocalories-BTUs-Foot-pounds-Ergs
question
Suppose that a person eats a diet of 2381 Calories per day.
Convert this energy into J.
answer
9.962×106
J Explanation: There are many different types of energy, but for the purposes of this question, we will use the SI unit of energy, the joule. A calorie is a unit of energy, but it is not an SI unit. A calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius. There are 4.184 joules in 1 calorie. So, to convert 2381 calories to joules, we would multiply 2381 by 4.184 to get 9999.924 joules.
question
Suppose that a person eats a diet of 2381 Calories per day.
Convert this energy into kJ.
answer
9962
kJ Explanation: A person eating 2381 Calories per day is consuming 9,932 kilojoules of energy each day.
question
Suppose that a person eats a diet of 2381 Calories per day.
Convert this energy into kWh.
answer
2.767
kWh Explanation: A person eating 2381 Calories per day is eating about 10,000 kilojoules per day. If we divide 10,000 by 24 hours in a day, we get about 417 kilojoules per hour, or 1.14 kilowatt-hours. So a person eating 2381 Calories per day is eating about 1.14 kilowatt-hours of energy.
question
A goose is flying south for the winter at a constant speed. Keep in mind that one mile is 1.61 km , and one pound is 454 g .
The goose has a mass of 21.4 lb (pounds) and is flying at 10.7 miles/h (miles per hour). What is the kinetic energy of the goose in joules?
answer
111
J Explanation: A goose is flying south for the winter at a constant speed. Keep in mind that one mile is 1.61 km, and one pound is 454 g. The goose has a mass of 21.4 lb (pounds) and is flying at 10.7 miles/h (miles per hour).To calculate the kinetic energy of the goose, we need to first convert the mass from pounds to kilograms, and the velocity from miles per hour to meters per second. We can do this by using the following conversion factors:1 lb = 0.454 kg1 mi/h = 1609 m/sNow that we have the mass and velocity in the correct units, we can plug them into the kinetic energy equation:KE = 1/2 * m * v^2KE = 1/2 * 21.4 kg * (1609 m/s)^2KE = 1/2 * 21.4 kg * 2.59 x 10^6 m^2/s^2KE = 5.48 x 10^5 kg * m^2/s^2KE = 5.48 x 10^5 J
question
Classify the following by the sign of ΔE for the system.
Drag the appropriate items to their respective bins. If no definitive classification can be made, drag the item into the bin labeled "Not enough data."
answer
Negative
- the system expands and the surroundings get hotter
Positive
- the system contracts and the surrounding get colder
Not enough data
- the system contracts and the surroundings get hotter
- the system expands and the surroundings get colder Explanation: A) ?E for the system is positiveB) ?E for the system is negativeC) ?E for the system is zeroD) Not enough dataA) ?E for the system is positiveB) ?E for the system is negativeC) ?E for the system is zeroD) Not enough data
question
An ideal gaseous reaction (which is a hypothetical gaseous reaction that conforms to the laws governing gas behavior) occurs at a constant pressure of 50.0 atm and releases 63.1 kJ of heat. Before the reaction, the volume of the system was 7.60 L . After the reaction, the volume of the system was 3.00 L .
Calculate the total internal energy change, ΔE, in kilojoules.
Express your answer with the appropriate units.
answer
ΔE =
-39.9 kJ Explanation: The ideal gas law states that PV = nRT, where P is the pressure, V is the volume, n is the number of moles of gas, R is the universal gas constant, and T is the temperature. In this question, we are given the pressure and the heat released, so we can solve for the change in internal energy.We know that the internal energy of a gas is given by U = nCvT, where Cv is the heat capacity at constant volume. We also know that Cv = R/2 for an ideal gas. Therefore, we can write?E = nCv?T = n(R/2)?TWe can solve for ?T by using the ideal gas law:?T = (PV/nR) - (PV/nR) = (50.0 atm * 3.00 L / 1 mol * 8.314 J/mol*K) - (50.0 atm * 7.60 L / 1 mol * 8.314 J/mol*K)= 300 K - 400 K = -100 KTherefore, the change in internal energy is given by?E = n(R/2)?T = (1 mol)(8.314 J/mol*K)(-100 K) = -831.4 J
question
An ideal gas (which is is a hypothetical gas that conforms to the laws governing gas behavior) confined to a container with a massless piston at the top. (Figure 2) A massless wire is attached to the piston. When an external pressure of 2.00 atm is applied to the wire, the gas compresses from 6.40 to 3.20 L . When the external pressure is increased to 2.50 atm, the gas further compresses from 3.20 to 2.56 L .
In a separate experiment with the same initial conditions, a pressure of 2.50 atm was applied to the ideal gas, decreasing its volume from 6.40 to 2.56 L in one step.
If the final temperature was the same for both processes, what is the difference between q for the two-step process and q for the one-step process in joules?
Express your answer with the appropriate units.
answer
162 J Explanation: The difference in q between the two-step process and the one-step process is 0.48 J.
question
Assuming constant pressure, rank these reactions from most energy released by the system to most energy absorbed by the system, based on the following descriptions:
Surroundings get colder and the system decreases in volume.
Surroundings get hotter and the system expands in volume.
Surroundings get hotter and the system decreases in volume.
Surroundings get hotter and the system does not change in volume.
Also assume that the magnitude of the volume and temperature changes are similar among the reactions.
Rank from most energy released to most energy absorbed. To rank items as equivalent, overlap them.
answer
Most energy released
B
D
C
A
Most energy absorbed Explanation: Surroundings get hotter and the system expands in volume. Surroundings get colder and the system decreases in volume. Surroundings get hotter and the system does not change in volume. Surroundings get hotter and the system decreases in volume.
question
A mole of X reacts at a constant pressure of 43.0 atm via the reaction
X(g)+4Y(g)→2Z(g), ΔH∘=−75.0 kJ
Before the reaction, the volume of the gaseous mixture was 5.00 L. After the reaction, the volume was 2.00 L. Calculate the value of the total energy change, ΔE, in kilojoules.
Express your answer with the appropriate units.
answer
ΔE =
-62.0 kJ Explanation:Surroundings get hotter and the system expands in volume. Surroundings get colder and the system decreases in volume. Surroundings get hotter and the system does not change in volume. Surroundings get hotter and the system decreases in volume.
question
Calculate the enthalpy of the reaction
2NO(g)+O2(g)→2NO2(g)
given the following reactions and enthalpies of formation:
12N2(g)+O2(g)→NO2(g), ΔH∘A=33.2 kJ
12N2(g)+12O2(g)→NO(g), ΔH∘B=90.2 kJ
Express your answer with the appropriate units.
answer
ΔH∘ =
-114.0 kJ Explanation: The enthalpy of the reaction 2NO(g)+O2(g)>2NO2(g) is given by the enthalpy of formation of NO2(g), ?H?A=33.2 kJ. The enthalpy of formation of NO2(g) is given by the reaction 12N2(g)+O2(g)>NO2(g). The enthalpy of formation of NO(g) is given by the reaction 12N2(g)+12O2(g)>NO(g).
question
Calculate the enthalpy of the reaction
4B(s)+3O2(g)→2B2O3(s)
given the following pertinent information:
B2O3(s)+3H2O(g)→3O2(g)+B2H6(g), ΔH∘A=+2035 kJ
2B(s)+3H2(g)→B2H6(g), ΔH∘B=+36 kJ
H2(g)+12O2(g)→H2O(l), ΔH∘C=−285 kJ
H2O(l)→H2O(g), ΔH∘D=+44 kJ
Express your answer with the appropriate units.
answer
ΔH∘ =
-2552 kJ Explanation: The enthalpy of the reaction 4B(s)+3O2(g)>2B2O3(s) is +1526 kJ.
question
Calculate the standard enthalpy change for the reaction
2A+B⇌2C+2D
Use the following data:
answer
ΔH∘rxn =
257 kJ Explanation: The standard enthalpy change for the reaction 2A+B鈫?C+2D is calculated using the standard enthalpies of formation of the products and reactants. The standard enthalpy of formation is the enthalpy change when one mole of a substance is formed from its constituent elements in their standard states.The standard enthalpy of formation of A is �,200 kJ/mol, the standard enthalpy of formation of B is �,000 kJ/mol, the standard enthalpy of formation of C is �,800 kJ/mol, and the standard enthalpy of formation of D is �,000 kJ/mol.Using the standard enthalpies of formation, the standard enthalpy change for the reaction 2A+B鈫?C+2D is calculated to be �,400 kJ/mol.
question
For the reaction given in Part A, how much heat is absorbed when 2.50 mol of A reacts?
Express your answer to three significant figures and include the appropriate units.
answer
321 kJ Explanation: The amount of heat absorbed can be calculated using the enthalpy of the reaction, which is -41.0 kJ/mol. This means that for every mole of A that reacts, 41.0 kJ of heat is absorbed. Therefore, for 2.50 mol of A that reacts, 2.50 x 41.0 = 102.5 kJ of heat is absorbed.
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