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Flashcards for Unit 12

Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

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Page 1: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Flashcards for Unit 12

Page 2: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Equilibrium

Rate of forward process=

Rate of reverse process

Page 3: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Conditions for Equilibrium

2-way processClosed System

Page 4: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Dynamic Equilibrium

Macroscopic level – looks constant.

Microscopic level – lots of action

Page 5: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Types of Equilibria

1) Physical: Phase & Solution2) Chemical

Page 6: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

A solution at equilibrium must be

Saturated

Page 7: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Phase Equilibrium

H2O(l) H2O(g)

Page 8: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Solution EquilibriumIonic Cmpd

NaCl(s) Na+(aq) + Cl-

(aq)

Page 9: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Solution EquilibriumCovalent Cmpd

C6H12O6(s) C6H12O6(aq)

Page 10: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

H2O(g) H2O(l)

Phase Equilibrium

Page 11: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

NH4Cl(s) NH4+(aq) + Cl-

(aq)

Solution Equilibrium

Page 12: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Chemical Equilibrium – Haber Synthesis

N2(g) + 3H2(g) 2NH3(g) + heat

Page 13: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

LeChatelier’s Principle

A system at equilibrium will respond to remove a

stress

Page 14: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

What’s a stress for a chemical system?

Change in temperature, pressure, or

concentration

Page 15: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Catalyst

Substance that increases the rate of a chemical reaction without itself

being consumed.

Page 16: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Catalyst

Does not shift the equilbrium point – the equilibrium

concentrations are the same. You just get to equilibrium

quicker.

Page 17: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

At what temperature can H2O(s) and H2O(l) exist in equilibrium?

0C or 273K

Page 18: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

At what temperature can H2O(g) and H2O(l) exist in equilibrium?

100C or 373K

Page 19: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Pressure Changes

Only affect systems that have a gas in them

Page 20: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

An increase in pressure favors which side?

CO2(g) CO2(aq)

When P , more CO2 dissolves!

Page 21: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

N2(g) + 3H2(g) 2NH3(g) + heat

Equilibrium shifts to right.Concentration of H2 .

Concentration of NH3 . Temperature

StressStress What happens?What happens?

Page 22: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

N2(g) + 3H2(g) 2NH3(g) + heat

Shifts to the side with fewer moles of gas, in this

case the right.

How does this system respond How does this system respond to an to an increaseincrease in pressure? in pressure?

4 moles 2 moles

Page 23: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

N2(g) + 3H2(g) 2NH3(g) + heat

Shifts to the side with more moles of gas, in this

case the left.

How does this system respond How does this system respond to a to a decreasedecrease in pressure? in pressure?

Page 24: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

H2(g) + I2(g) + heat 2HI(g)

This system has the same # of moles on each side.

It cannot respond to pressure changes.

How does this system respond How does this system respond to a to a decreasedecrease in pressure? in pressure?

2 moles 2 moles

Page 25: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

NaCl(s) Na+(aq) + Cl-(aq)

This system has no gases. It does NOT respond to

pressure changes.

How does this system respond How does this system respond to a to a changechange in pressure? in pressure?

Page 26: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

N2(g) + 3H2(g) 2NH3(g) + heat

Equilibrium shifts to the left.

Concentration of N2 & H2 . Temperature .

Stress

What happens?What happens?

Page 27: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

N2(g) + 3H2(g) 2NH3(g) + heat

Equilibrium shifts to the right. Concentration of N2 & H2 .

Temperature .

Stress

What happens?What happens?

Page 28: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

N2(g) + 3H2(g) 2NH3(g) + heat

Equilibrium shifts to the left. Concentration of N2 . Concentration of NH3 .

Temperature .

Stress

What happens?What happens?

Page 29: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Exothermic Reaction

Energy is released: It flows from system to

environment. Temperature of environment increases.

Page 30: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Endothermic Reaction

Energy is absorbed: It flows from environment to system. Temperature of environment

drops.

Page 31: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Heat of reaction, H

Hproducts - Hreactants

Page 32: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

The difference between the potential energy of the products & the potential energy of the reactants?

Hproducts – Hreactants or H

Page 33: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

H for exothermic rxn

H is negative. System has net loss in energy.

Page 34: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

H is negative?

Exothermic reaction. Products have less

potential energy than reactants.

Page 35: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

H is positive?

Endothermic reaction. Products have more potential

energy than reactants.

Page 36: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

H for endothermic rxn

H is positive. System has net gain in energy.

Page 37: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

A + B C + D + heat

Exothermic Reaction. Heat term is on product

side.

Page 38: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

A + B + heat C + D

Endothermic Reaction. Heat term is on reactant

side.

Page 39: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Which phase change is endothermic?

a) Gas to liquidb) Gas to solidc) Solid to gasd) Liquid to solid

Page 40: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Which phase change is exothermic?

a) Solid to gasb) Liquid to gasc) Solid to liquidd) Liquid to solid

Page 41: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

A reaction occurs in water & the

temperature of the water increases.

Endo or Exo?

Exothermic

Page 42: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

A reaction occurs in water & the

temperature of the water decreases.

Endo or Exo?

Endothermic

Page 43: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

A + B C + D. H = -45 kJ.

What is H for C + D A + B?

H = +45 kJ

Page 44: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

A + B C + D. H = -45 kJ.

What is H for: 2A + 2B 2C + 2D?

H = -90 kJ

Page 45: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Entropy

Degree of disorder or chaos in a system.

Page 46: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Entropy

The more degrees of freedom a system has, the higher

the entropy.

Page 47: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

S

Entropy

Page 48: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

H

Enthalpy or

Chemical Potential Energy

Page 49: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

0 entropy?

A perfect crystal at 0K

Page 50: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

S

Change in entropySproducts – Sreactants

Page 51: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Which phase has the greatest entropy?

Gas phase – the molecules have more ways of moving

& more places to be!

Page 52: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Which phase has the greatest entropy?

Sgas >> Sliquid > Ssolid

Page 53: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Did the entropy increase or decrease?

NaCl(s) Na+(aq) + Cl-(aq)

Increase!

Page 54: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Did the entropy increase or decrease?

CO2(g) CO2(aq)

Decrease!

Page 55: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Did the entropy increase or decrease?

2H2O(l) 2H2(g) + O2(g)

Increase!

Page 56: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Spontaneous Process

Physical or Chemical change that occurs with no outside

intervention. (Supplying activation energy does not

count!)

Page 57: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Nature is lazy & disorganized.

Nature favors:Negative value for H: Net lossPositive value for S: Net gain

Page 58: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

When will a change never occur?

When both factors go against nature:Positive value for H: Net gain in

energy.Negative value for S: Net loss in chaos

Page 59: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Endo: starts low, ends high

Endo or Exo?

Page 60: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Exo: starts high, ends low

Endo or Exo?

Page 61: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Reactants

Identify reactants, products, activated complex

Activated Complex

Products

Page 62: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Potential energy of reactants

Identify the arrow

Page 63: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Activation energy of forward rxn

Identify the arrow

Page 64: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Heat of reaction

Identify the arrow

Page 65: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Activation energy of reverse reaction

Identify the arrow

Page 66: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Potential energy of activated complex

Identify the arrow

Page 67: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Potential energy of products

Identify the arrow

Page 68: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Collision Theory

Effective collisions between reacting particles must

occur for a reaction to take place.

Page 69: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Effective Collisions

EnergeticFavorable Orientation

Page 70: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Rate of reaction

The speed of the reaction. The faster it occurs, the

greater the rate.

Page 71: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Breaking Bonds …

Absorbs Energy

Page 72: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Making Bonds …

Releases Energy

Page 73: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

6 Factors that influence the rate of reaction

Nature of reactants (ionic or covalent)TemperatureConcentrationPressure (for gases)Surface area (for heterogeneous

reactions)Presence of a catalyst

Page 74: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Raising the temperature increases the reaction rate by

Increasing both the number of collisions and the efficiency of

the collisions.

Page 75: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

As the concentrations of the reactants , the rate of rxn …

increases

Page 76: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

As the pressure on gas-phase reactants , the rate of rxn …

Increases.

Page 77: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Which 4.0-gram Zn sample will react faster with acid,

and why?

a)Lumpb)Barc)Powderedd)Sheet metal

More surface area

Page 78: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

How does a catalyst work?

Provides an alternate reaction pathway with a lower activation energy.

Page 79: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Does a catalyst change H?

NO.

Page 80: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Which reacts faster: ions in solution or covalent

molecules?

Ions in solution.

Page 81: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Which reacts faster in water: 1 cm3 of Na or 1 cm3 of Ca?

1 cm3 of Na - Nature of the metals

Page 82: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Which is usually slower, an organic reaction or an

inorganic reaction?

Organic, because organic particles contain covalent

bonds.

Page 83: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Lowers the activation energy.

Effect of a catalyst?

Page 84: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Potential energy of reactants

Identify the arrow

Page 85: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Activation energy of forward rxn

Identify the arrow

Page 86: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Activation energy of reverse rxn

Identify the arrow

Page 87: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Potential energy of activated complex

Identify the arrow

Page 88: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Heat of reaction

Identify the arrow

Page 89: Flashcards for Unit 12. Equilibrium Rate of forward process = Rate of reverse process

Potential energy of products

Identify the arrow