Unit 7 Kinetics and Thermodynamics ReviewReview

Unit 7 Kinetics and ThemochemistryLaws of Thermodynamics

___________________: the part of the universe on which you focus your attention.

__________________________: the part of the universe that includes everything else in the universe.

_______________________ = system + surroundings

First law of thermodynamics states that the total amount of energy in the universe is constant. This defines the ___________________________________________________________.

Second law of thermodynamics states that the disorder in the universe always increases. As the disorder in the universe increases, the energy is transformed into less usable forms. This energy is called ___________________Thus, the efficiency of any process will always be less than 100%.

Third law of thermodynamics states that all molecular movement stops at a temperature we call _____________ ______________, or 0 Kelvin (-273°C). Since temperature is a measure of molecular movement, there can be no temperature lower than absolute zero. At this temperature, a perfect crystal has ____________________________..

Vocabularyactivation energy boiling point catalyst condensation deposition freezing point entropyenthalpy evaporation melting point phases solidification spontaneous sublimation vaporization molar heat of fusion molar heat of vaporization Gibbs free energy Heat of reaction

1. The process of a liquid becoming a gas is called _______________________.

2. The amount of energy needed to vaporize one mole of liquid at its boiling point is called the liquids

_________________________.

3. The process of a solid becoming a gas is called _______________________.

4. Gas, Liquid, and solid are the three ______________ of matter.

5. The process of a solid becoming a liquid is called _______________________.

6. The temperature at which a liquid becomes a gas is its __________________________.

7. The amount of energy needed to melt one mole of solid at its melting point is called the solids

____________________________________.

8. The process of a gas becoming a solid is called _______________________.

9. The temperature at which a liquid becomes a solid is its _________________________.

10. The process of a gas becoming a liquid is called _______________________.

11. The process of a liquid becoming a gas at its boiling point is called _______________________.

12. The temperature at which a solid becomes a liquid is its _________________________.

13. ______________________ changes take place by themselves, without any help.

14. The ____________ __ _______________ or _____________ is used to describe how much energy is produced or used during a chemical change.

15. The measure of randomness in a system is called ________________.16. _____________ _______________ ______________ (∆G) stands for the value equal to the enthalpy minus the

temperature times entropy. It can be used to determine if a reaction will take place spontaneously.

17. A _____________________ is used to lower the energy required to make a reaction take place. It makes chemical

reactions go faster without being consumed.

18. ___________________ ___________________ is the amount of energy which a system has to have in order for a

chemical change to take place.

Intermolecular Forces and Phase Changes Brinkmann 2011

When IMF are…

volatility is ____________

vapor pressure_______

boiling point is __________

volatility is __________

vapor pressure is ______

boiling point is __________

weak strongg

Unit 7 Kinetics and Thermodynamics ReviewReview

1. Intramolecular are forces of attraction within molecules.a. _______________ bonds are between metal and non–metal ions. They involve a transfer of electrons from the

metal to the non-metal element.

b. _______________ bonds are non-metal elements sharing electrons.

Determine if each of the following bonds would be ionic, polar covalent or nonpolar covalent.

a. H – P

b. Mg – Cl

c. P – O

d. C – H

e. Li – Br

f. N –N

2. Intermolecular are the forces of attraction between molecules.

a. Hydrogen bonding (strongest, a very polar bond between hydrogen and either nitrogen, oxygen or fluorine. Eg. H2O,

NH3)

b. Dipole forces (second strongest, occurs with polar molecules). Eg. HCl

c. Dispersion (weakest, occurs in nonpolar molecules, results from electrons within the molecule being re-distributed so

there is a temporary dipole). Eg. C2H4

3. What is the dominant (most important) type of intermolecular force for each of the following compounds?

a. NH3

b. CH4

c. HCl

d. F2

e. H2O

f. H2

g. H2S

h. NO2

i. Cl2

j. HF

4. Fill in the diagram (with high or low) to show how intermolecular forces influence the volatility, vapor pressure, and boiling point of a substance.

5. Volatility is

6. Vapor pressure is

Does entropy INCREASE or DECREASE with the following phase changes. Describe molecule motion and energy.

7. As methanol (l) solidifies (s) ________________________________________________________________

8. As ice (s) turns to vapor (g) ________________________________________________________________

9. As water (g) condenses (l) ________________________________________________________________

10. As water (l) vaporizes (g) ________________________________________________________________

11. As a metal (s) melts to liquid (l) ________________________________________________________________

12. As methanol (g) turns to methanol (s) _________________________________________________________

Brinkmann 2011

Unit 7 Kinetics and Thermodynamics ReviewReview

Phase Diagrams_________________ is a dynamic condition in which two opposing changes occur at equal rates in a closed system.

Change in the state of matter always involves a change in ________________________.

A phase diagram is a graph of pressure versus temperature that shows the conditions under which the phases of a

substance exist.

The ____________ _________ of a substance indicates the temperature and pressure at which all three phases coexists

at equilibrium.

The _________________ _______________ is the

temperature above which the substance cannot exist in a

liquid state.

1. The AB line is the ___________________ interface.

2. It starts at the _________________ (A), the point at

which all three states are in equilibrium.

3. It ends at the _______________ (B); above this

critical temperature and critical pressure the liquid

and vapor are indistinguishable from each other.

4. Each point along this line is the ______________ of the substance at that pressure.

5. The AD line is the interface between ______________________________.

6. The ________________ at each pressure can be found along this line.

7. Below A the substance cannot exist in the __________________.

8. Along the AC line the ______________ phases are in equilibrium; the ____________________ point at each

pressure is along this line.

9. How would you describe the change in the substance as the conditions

change from Letter F to Letter G?

10. How would you describe the change in the substance as the conditions

change from Letter E to Letter G?

11. Letter C represents the _____________ ______________. The substance

cannot be in the ____________ phase above this temperature.

12. Letter B represents the _______________ ______________. This is the conditions where __________, _________,

and ________ are present.

Brinkmann 2011

Substance Specific Heat (J/goC)

H2O (l) 4.184H2O (steam) 2.02Al (s) 0.89Fe (s) 0.45

WaterHeat of fusion = 334 J/gHeat of vaporization = 2260 J/g

q = m·C·T

q = heat energym = mass of waterC = the specific heat capacityT = the change in temperature (in °C or K)

Unit 7 Kinetics and Thermodynamics ReviewReview

CalorimetryMeasuring heat (formerly measured in calories) is called ______________________. In the metric system, heat energy is

measured in in ____________________(J). The equation we use is:

1. How much heat energy is needed to raise the temperature of a 55 g sample of aluminum from –24 °C to 94.6 °C?

2. 5.5 KJ of heat are added to an unknown 25 grams sample. The temperature of the water is raised from 25K to 247 K. What is the unknown substance?

3. 3.5 KJ of heat are added to a 28.2 g sample of copper at 20°C. What is the final temperature in kelvins? Specific heat of copper is 0.0385 J/g °C

In the heating and cooling curves tutorial we learned that energy is absorbed by a substance as it warms up, melts (fusion) or boils (vaporization) and energy is released from a substance as it cools down, condenses, or freezes.

Calorimetry (q=mCT) allows us to calculate the energy changes as a substance warms or cools. (1, 3, & 5)

The energies involved in phase changes (areas 2 & 4) are the Heat of Vaporization (liquid gas) and the Heat of Fusion (solid liquid). These energies will be used as conversion factors.

4. How much heat is necessary to change a 52.0 g sample of steam at115.0 °C into ice at -30.0 °C? This problem requires several steps since temperature changes and a phase change takes place. Use the hints to solve.a. Draw a graph of the change in temperature. Number each segment.

b. Steam to heat of vaporization:

c. Heat change during phase change:

d. Heat change as water:

e. Heat change during phase change:

f. Heat change for cooling of ice

g. Calculate the total energy change (exothermic or endothermic?).

Energy Change in Chemical ReactionsBrinkmann 2011

Elementary Steps Enthalpy (∆H) 2NO2(g) + 7H2(g) → 2NH3(g) + 4H2O(l) ∆Ho = 142.5 kJ2NO2(g) → N2(g) + 2O2(g) ∆Ho = 82.5 kJH2O(l) → H2(g) + ½ O2(g) ∆Ho = -43.7 kJ

Unit 7 Kinetics and Thermodynamics ReviewReview

1. Calculate the amount of heat produced when 34.8 g of methane, CH4, burns in excess of oxygen, according to the following equation: CH4 + 2 O2 → CO2 + 2 H2O ΔH = ‐890.2 kJ

2. How much heat will be transferred when 5.81g of graphite reacts with excess H2 according to the following equation? Is the reaction endothermic or exothermic? 6C+ 3H2 → C6H6 ∆Ho = 49.03kJ

Ans: 3.95 kJ

3. How much heat will be released when 1.48g of chlorine reacts with excess phosphorous according to the following equation? Is the reaction endothermic or exothermic? 2P + 5Cl2 → 2PCl5 ∆Ho = -866kJ

Ans: -3.62 kJ

4. How much heat will be released when 4.77g of ethanol (C2H5OH) reacts with excess O2 according to the following equation? Is the reaction endothermic or exothermic? C2H5OH + 3O2 → 2CO2 + 3H2O ∆Ho = -791.4kJ

Ans: -81.9 kJ

5. What is the change in enthalpy when 11.8g of iron reacts with excess O2 according to the following equation? Is the reaction endothermic or exothermic? 3Fe + 2O2 → Fe3O4 ∆Ho = -1120.48kJ

Ans: -78.9 kJ

6. How much heat will be transferred when 14.9g of ammonia reacts with excess O2 according to the following equation? Is the reaction endothermic or exothermic? NH3 + 5O2 → 4NO + 6H2O ∆Ho = -1170kJ

Ans: -256 kJ

Hess’s Law

7. Calculate the standard reaction enthalpy for the photosynthesis reaction.

6 CO2(g) + 6 H2O(l) C6H12O6(s) + 6 O2(g) = ? kJ Ans: 2801.3 kJ

8. Use the thermochemical equations shown below to determine the enthalpy for the reaction for N2(g) + 3H2(g) → 2NH3(g)Ans: -114.8 kJ

Brinkmann 2011

Substance Enthalpy (∆H) C6H12O6(l) -1274.5 kJ/molO2(g) 0 kJ/molCO2(g) -393.5 kJ/molH2O(l) -285.8 kJ/mol

Unit 7 Kinetics and Thermodynamics ReviewReview

Energy DiagramsClassify the following as endothermic, exothermic or neither:_____ surroundings get hot

_____ PE diagram is uphill

_____ energy is a product

_____ H is positive

_____ reactants have more energy

_____ H is negative

_____ PE diagram is downhill

_____ surroundings get cold

_____ products have more energy

_____ energy is a reactant

Potential Energy Diagrams

1. Is this chemical reaction endothermic or exothermic?

2. What is the activation energy for this reaction?

3. What is the heat of reactants?

4. What is the energy of the activated complex?

5. What is the heat of the products?

6. What is the heat of the reaction or enthalpy?

Energy Diagram II

7. Is this chemical reaction endothermic or exothermic?

8. What is the activation energy for this reaction?

9. What is the heat of reactants?

10. What is the energy of the activated complex?

11. What is the heat of the products?

12. What is the heat of the reaction or enthalpy?

Potential Energy Diagram III

13. Draw an energy diagram

Heat of reactants: 175 KJ Heat of products: 50 KJ

Energy of activated complex: 225 KJ

Heat of reaction: _____ KJ Activation Energy: ______ KJ

14. Is this reaction endothermic or exothermic?

15. If a catalyst is present for this reaction, how would the energy diagram change? Show this on your diagram.

Chemistry 1-2 Brinkmann

Energy Diagram I

Energy Diagram II

Energy Diagram III

Unit 7 Kinetics and Thermodynamics ReviewReview

Collision TheoryC6H12O6 (s) + 6 O2(g) → 6 H2O (g) + 6 CO2 (g)

1. What happens to the concentrations of:a. C6H12O6 & O2 as the reaction proceeds?

b. H2O + CO2 as the reaction proceeds?

2. According to the collision theory, what 3 circumstances are needed for C6H12O6 & O2 to react?a.

b.

c.

3. What is the activation energy for a chemical reaction?

Use the collision theory to explain the following:

Change in condition Increases/Decreases Explain why.

a. Increasing the temperatureEx: Increases (speeds up)

Ex: Molecules move faster; more molecules collide with greater energy; activation energy

b. Increasing the concentration of C6H12O6

c. Decreasing the concentration of O2

d. Increase the surface area by chewing up food in your mouth

e. Decreasing the temperature

f. Increasing the pressure in the container

g. Decreasing the concentration of H2O

h. Increasing the volume of the container the reaction occurs in

i. Increasing the concentration of CO2

j. Using a catalyst (like salivary amylase)

Reaction MechanismsThe series of steps by which a chemical reaction occurs is the ______________

_________________. Each individual chemical reaction is called an ____________

_____________. The product of an elementary reaction is an __________________.

An intermediate is a product that immediately gets used in the next reaction. The

elementary reaction with the highest _________________ ___________ has the

lowest rate and is the ________ _______________ ____________.

Chemistry 1-2 Brinkmann

Time Temperature(Sec) (°C)

0 21.110 25.620 30.230 32.440 33.650 34.660 35.0

Unit 7 Kinetics and Thermodynamics ReviewReview

Rate of Reaction

1. A pieces of magnesium reacts with 10 ml of 1 M hydrochloric acid. What is the rate of the reaction? Assume the magnesium is 0.15 grams.a. Graph the data.

b. Calculate the overall rate of the reaction.

c. Calculate the rate of the reaction between 0 and 30 seconds.

d. Calculate the heat of the reaction based on 10 ml of water (Cp = 4.184 J/gK).

e. Is this reaction endothermic or exothermic?

2. In the gas-phase reaction I2 + Cl2 →2Cl, the [I2] changes from 0.400 M at time = 0 to 0.300 M at time = 4 .00 min. Calculate the average reaction rate in moles I2 consumed per liter per minute.

3. At a given temperature and for a specific time interval, the average rate of the following reaction is 1.88 x 10 -4 moles N2 consumed per liter per second. Express the reaction rate in moles H2 consumed per liter per second and in moles NH3 produced per liter per second.

N2 + 3H2 → 2NH3

4. Given the following data for the decomposition of hydrogen peroxide, calculate the average reaction rate in moles H2O2 consumed per liter per minute for each time interval.

Chemistry 1-2 Brinkmann

Time (min) Concentration H2O2 (M)

0 2.52 2.125 1.8210 1.4820 1.0