CHEM 001 Lecture Notes - Lecture 20: Enthalpy, Closed System, Invariant Mass

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skywildebeest596

13 Aug 2020

School

College of The Sequoias

Department

Chemistry (CHEM)

Course

CHEM 001

Professor

Rodriguez

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Document Summary

At constant pressure, h = u + p v. D. h = change in heat of a reaction. When comparing a sample of gases, the highest number of molecules has the highest entropy value. When the number of molecules are equal, must compare bonds, e. g. o(g) > Due to s = dqrev/t, the rate of energy change increases with decreasing temperature, but the rate is still going forward. If a reaction increases the number of gaseous molecules, entropy = positive (for the reaction system, not necessarily the surroundings or universe) Every variable above refers to the system and not the surroundings. B. g = 0 = equilibrium at: The smaller the k for the reaction (with the positive g) Definition: the collective energy of molecules on a microscopic scale. Internal energy does not include mechanical energy; that is, it is all possible forms of energy on the molecular scale.

Related Questions

Atoms can bond to other atoms to make molecules. Atoms sometimes break these bonds and form them in a different way. For example, it is possible to take two molecules of hydrogen (H_2) and one molecule of oxygen (O_2), put them near one another, give them a little spark to help them start a reaction, and you will end up with two molecules of water (H_2O). Do you see what happened? Some of the H-H bonds and the O-O bonds broke and were replaced by O-H bonds. The process of forming or breaking bonds is called a chemical reaction. Chemical reactions come in a vast variety of types. But they typically involve energy changes that are, very roughly, 5 times 10^-19 J per molecule. We can use that number to estimate some useful quantities. Be sure to write your units in the answers below. Gasoline is made up of molecules with carbon and hydrogen (C and H). There are many kinds of molecules in a typical gasoline; but let's assume that all of them are in the form of C_8H_17. That substance has a mass of 18 times 10^-26 kg per molecule. If the mass density of gasoline is 720 kg/m^3, then how many molecules are in one gallon of gasoline? (1 m^3 = 264 gallons.) Please show your work and don't just look it up on the web. Here's a keep track of your units. At the end, the units should cancel out and your answer for the number of molecules should have no units. When you burn gasoline, you convert chemical energy to heat or work (to make your car move). If, when you burn gasoline, you convert 5 times 10^-19 J per molecule, how much energy can be obtained from one gallon of gasoline? If your car has a mass of 1,000 kg, then how much energy is needed to make your car go from rest to 65 mph (29 m/s)? (Think of this using kinetic energy. Ignore friction with the air or road.) How many gallons of gasoline are needed to make your car go from rest to 65 mph (29 m/s). (This is a rough estimate, neglecting the energy lost to air friction, heat, and other things.) If gasoline costs $2.20 per gallon, how much money does your answer to part (d) cost ?

When performing a calorimetry experiment, a metal is heated to100^oC and then immersed in a Styrofoam cup containing100g of water at a temperature of 22^oC. Describe thetransfer of heat assuming none is lost to theenvironment.

Heat will transfer from the water to the metal increasing thetemperature of the metal.
Heat will transfer from the water to the metal decreasing thetemperature of the water.
Heat is transferred from the metal to the water in an endothermicfashion with respect to the metal.
Heat is transferred from the metal to the water in an exothermicfashion with respect to the metal.
No heat is transferred because heat is not lost to theenvironment.

The Ideal Gas Law is PV= nRT. Which of the following relationshipsis (are) true for gases?

The number of moles of a gas is directly proportional to itsvolume (at constant pressure).
The pressure of a gas is inversely proportional to itstemperature in Kelvins (at constant volume).
The volume of a gas is directly proportional to its pressure(at constant temperature).

1 only
2 only
3 only
1 and 2
2 and 3

Ammonia is prepared by reacting nitrogen and hydrogen gases athigh temperature according to the unbalanced chemical equationbelow.

_ N₂(g) + _H₂(g) Ã¢â â_NH₃(g)

What are the respective coefficients when the equation isbalanced with the smallest whole numbers?

1,1,1
1,3,1
1,3,2
2,1,2
2,3,2

The combustion of propane produces carbon dioxide and steam.

C₃H₈(g) + 5O₂(g) Ã¢â â 3CO₂(g) + 4H₂O(g)

All the following statements concerning this reaction arecorrect EXCEPT

Three molecules of carbon dioxide are formed per one molecule ofpropane consumed.
Five molecules of oxygen are consumed per one molecule propaneconsumed.
Four moles of steam are formed per five moles of oxygenconsumed.
The combined mass of reactants consumed equals the mass of productsformed.
Three grams of carbon dioxide are formed per five grams of oxygenconsumed.

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CHEM 001 Lecture Notes - Lecture 20: Enthalpy, Closed System, Invariant Mass

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