CHEM 1C Lecture Notes - Lecture 2: Process Function, State Function, Joule

56 views2 pages

orangeturtle174

16 Nov 2017

School

UCSC

Department

Chemistry and Biochemistry

Course

CHEM 1C

Professor

Peter Weiss

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Heat (q) and work (w): path function. All changes in energy of a system involve heat and/or work. Q and w are path functions: vary depending on state values across the entire process. E is a state function: it"s independent of the path taken, and only depends on the initial and final values of state variables. From point of view of the system! Positive w: work flows into the system, the surroundings do work on the system. Negative w: work flows out of the system, the system does work on the surroundings. If t=0, then e = 0 = w + q, so w = -q for isothermal process. 1200 j = -400 j + w. A gas is heated by adding 120 kj to it, and it"s allowed to expand, doing 90 kj of work on the surroundings. E = q + w = 120 kj + (-90) kj = 30 kj.

Related Questions

Calculate ∆E and determine whether the process is endothermic or exothermic for the following cases: (a) q = 0.763 kJ and w = –840 J. (b) A system releases 66.1 kJ of heat to its surroundings while the surroundings do 44.0 kJ of work on the system.

jadeshark113

1.According to the following thermochemical equation, if 31.1 g of NO2 is produced, how much heat is released at constant pressure?how much heat is released at constant pressure?

2NO(g) + O2(g) â 2NO2(g);ÎHÂ° = â114.4 kJ

Select one:

a. 114.4 kJ114.4 kJ

b. 1.183Ã103kJ

c. 2.365Ã103kJ

d. 38.7 kJ

e. 1.088Ã105kJ

2.CalculateâââÎUâââof a gas for a process in which the gas absorbs ââ12 J ââof heat and does ââ20 Jââ of work by expanding.

Select one:

a. 8 J

b. 32 J

c. -32 J

d. 0, because âÎU is a state function

e. -8 J

3.If q = +56 kJ for a certain process, that process

Select one:

a. requires a catalyst.

b. is exothermic.

c. occurs rapidly.

d. is endothermic.

e. cannot occur.

4.If q = 18 kJ and w = 15 kJ for a certain process, that process

Select one:

a. requires a catalyst.

b. has an increase in internal energy.

c. occurs slowly.

d. is exothermic.

e. cannot occur.

5.What is the change in internal energy of the system (ÎU) if 10 kJ of heat energy is released by the system and â70 kJâ of work is done on the system for a certain process?

Select one:

a. â60 kJ

b. 80 kJ

c. 10 kJ

d. 60 kJ

e. â80 kJ

6.What is the quantity of heat evolved at constant pressure when ââ26.3 gââ H2O(l)ââ is formed from the combustion of H2(g) and O2(g)?

2H2(g) + O2(g) â 2H2O(l);ÎHÂ° = â571.6 kJ

Select one:

a. 15033 kJ

b. 15.03 kJ

c. 1.72Ã104âkJ

d. 417.6 kJ

e. 9.57Ã102âkJ

7.What quantity, in moles, of hydrogen is consumed when 76.8 kJ of energy is evolved from the combustion of a mixture of H2(g) and O2(g)?

H2(g) + O2(g) â2H2O(l);ÎHÂ° = â571.6 kJ

Select one:

a. 2.368 mol

b. 1.184 mol

c. 0.4223 mol

d. 0.2687 mol

e. 1.368 mol

8. Which of the following is an exothermic process?

Select one:

a. work is done by the system on the surroundings

b. heat energy flows from the system to the surroundings

c. work is done on the system by the surroundings

d. heat energy is absorbed by the system

e. none of the above

9. Which of the following statements is correct?

Select one:

a. Internal energy is not a state function.

b. The value of q is negative when heat flows into a system from the surroundings.

c. The value of q is negative in an endothermic process.

d. Heat flows from a system into the surroundings in an exothermic process.

e. Enthalpy is not a state function.

10.X2and F2react according to the following equation, forming XF. (X is an unknown diatomic element)

X2(g)+ F2(g)â2XF(g);ÎHÂ°=+271 kJ

If X2(g) and F2(g) were mixed in a thermally insulated vessel, the reaction that occurred would be

Select one:

a. endothermic, and the temperature of the reaction system would fall.

b. We could not tell unless the original and final temperatures were given.

c. exothermic, and the temperature of the reaction system would fall.

d. exothermic, and the temperature of the reaction system would rise.

e. endothermic, and the temperature of the reaction system would rise.

Energy cannot be created nor destroyed, but it can be transferred between a reaction and its surroundings. The change in energy, Delta E, is positive if the reaction absorbs energy, and it is negative if the reaction releases energy. You may also see this expressed in terms of change in internal energy, Delta U. For the purposes of this question, Delta U and Delta E are equal. One way a reaction can transfer energy to or from the surroundings is by releasing or absorbing heat. A reaction can also transfer energy, in the form of work, through a change in volume. The total change in energy is the sum of the heat and work: Delta E = q + w At constant pressure, q = Delta H and w = -P Delta V and so Delta E = Delta H - P Delta V 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. Energy cannot be created nor destroyed, but it can be transferred between a reaction and its surroundings. The change in energy, Delta E, is positive if the reaction absorbs energy, and it is negative if the reaction releases energy. You may also see this expressed in terms of change in internal energy, Delta U. For the purposes of this question, Delta U and Delta E are equal. One way a reaction can transfer energy to or from the surroundings is by releasing or absorbing heat. A reaction can also transfer energy, in the form of work, through a change in volume. The total change in energy is the sum of the heat and work: Delta E = q + w At constant pressure, q = Delta H and w = -P Delta V and so Delta E = Delta H - P Delta V A mole of X reacts at a constant pressure of 43.0 atm via the reaction X(g) + 4Y(g) - 2Z(g), Delta H degree = -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. AE, in kilojoules. Express your answer with the appropriate units.

CHEM 1C Lecture Notes - Lecture 2: Process Function, State Function, Joule

Document Summary

Get access

Related textbook solutions

Chemistry: Structure and Properties

Basic Chemistry

Principles of Chemistry Molecular Approach

Principles of Chemistry Molecular Approach

Chemistry: Structure and Properties

Chemistry: A Molecular Approach

Chemistry: A Molecular Approach

Principles of Chemistry: A Molecular Approach

Chemistry: The Central Science

Related Documents

CHEM 1C Lecture Notes - Lecture 1: Chemical Potential, Intermolecular Force, Gas Constant

CHM 143 Lecture Notes - Lecture 17: Calorimeter, Calorimetry, Chemical Energy

CHEM 1000 Lecture Notes - Lecture 4: Calorimeter, Process Function, Joule

Related Questions