CHEM 131 Study Guide - Midterm Guide: State Function, Thermodynamics, Ionic Compound

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ochrepanda530

18 May 2020

School

University of Maryland

Department

Chemistry and Biochemistry

Course

CHEM 131

Professor

Monique Koppel

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Document Summary

First law of thermodynamics: the law of energy conversion; the total energy in the universe is constant energy is neither created nor destroyed. Esys is negative and energy flows out of the system into the surroundings: if the reactants have a lower internal energy than the products, Esys is positive and the energy flows into the system from the surroundings. Heat and work: e=q+w q(heat) w(work) E (change in internal energy) + energy flows into the system. Work: pressure- volume work: the work that occurs when a volume change takes place against an external pressure: v = a x h, w = -p x v. E=q work will not be calculated in change in energy: since the reaction occurs under onditions of constant volume qrxn/mol = erxn. Enthalpy: the heat evolved in a chemical reaction at constant pressure: h = qp, h = e x pv, h = e + p v.

Related Questions

1.) Which statement isincorrect?

(a) Energy is the capacity todo work or to transfer heat.

(b) Kinetic energy is theenergy of motion.

(d) A process that absorbsenergy from its surroundings is called exothermic.

(e) The Law of Conservation of Energy is another statement of the FirstLaw of Thermodynamics.

2. Which of the following statementsabout the first law of thermodynamics and energy is false?

(a)Kinetic energy cannot be convertedto potential energy.

(b)Kinetic energy =1/2mv².

(c)All the energy in the universe isconserved.

(d)A system can never decrease itsenergy.

(e)Potential energy is the energy ofposition or composition.

3. Whichone of the following thermodynamic quantities isnot a state function?

(a)work (b) enthalpy (c)entropy (d) internalenergy (e) free energy

As entropy increases there will be more useful energy to doâworkâ. True or false?

False. As entropy increases, there will generally be less usefulenergy to do work. We can think of entropy as usually being presentin the form of heat energy. Imagine a car motor, which attempts toturn chemical potential energy into kinetic energy (movement). Lessefficient motors will get hotter for the same amount of fuelconsumed. When you drive a car you hope that most of the fuelenergy is converted into kinetic energy and not lost as heat(entropy). The hotter the car (and thus the more entropy) the lessefficient the ability to do âworkâ (the moving of the vehicle).

True. As entropy increases, there will generally be more usefulenergy to do work. We can think of entropy as usually being presentin the form of heat energy. In most biological and mechanicalsystems it is heat energy which is captured to do useful 'work'.Heat energy, the random movement of molecules, and increases inentropy are central to doing useful work.

Biological systems sometimes appear on the surface to break theSecond Law of Thermodynamics â by seemingly increasing the order inthe overall system. They donât. Why?

a. Earth (and living things on it) are not a closed system. Thesun's constant input of energy in the form of photons is harnessedby living things to create internal order within themselves. Butwithout such a constant input of energy, most biological systems onearth would break down.

b. The Second Law tells us that no natural process can occurunless it is also associated with an increase in the entropy of theuniverse. A living organism (such as an animal or plant) brings inmatter and energy from its environment and uses this to creategreater order within its body: the processes of life. But it isimportant to keep in mind that all animals and plants are also partof a larger system of the environment around them. While creating asmall âpocketâ of order, the processes of life (metabolism,movement, etc..) releases heat into the environment â thusincreasing the entropy of the universe and following the2^nd law.

c. Living things, by harnessing energy to create order (withinand around themselves) actually create a paradox in questionssurrounding the first and second laws of thermodynamics andseemingly violate many previously held assumptions.

d. Both a and b above are correct.

When plants capture energy in the photons of sunlight andconvert that energy into the chemical bonds of organic molecules,are they creating new energy?

No, the energy is being transferred from one form into another.But no new energy is being created.

No, the overall total energy is decreasing over time.

Yes, by capturing photons, the plants are creating newenergy.

Yes, by capturing photons, the plants are creating new energy -of a different wavelength.