quiz 1 Flashcards

1
Q

What is energy

A

Capacity to do work or produce heat

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2
Q

What are the two types of energy

A

Potential: due to position or composition
Kinetic: due to motion of an object (KE=1/2 mv^2)

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3
Q

What makes up internal energy

A

E = PE + KE

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4
Q

What does nature prefer

A

A lower energy state

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5
Q

Describe thermochemistry

A

Deals with heat effects accompanying chemical reactions

Always a flow of heat into or out of the system

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6
Q

Describe thermodynamics

A

Study of energy and its conversion into different forms

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7
Q

What is a system

A

Part of universe we focus our attention on

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8
Q

What is the surrounding

A

Everything else in the universe

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9
Q

What is temperature

A

Describes the random motion of particles in a substance
Higher temperature = greater motion
KEavg = 3/2 RT for an ideal gas

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10
Q

What is heat

A

Transfer of thermal energy between two objects due to a temperature difference (q or Q)
Flow from area of higher temperature to lower
Collisions push to object at lower temperature

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11
Q

What is work

A

A force acting over a distance, usually in joules, some energy is converted to heat because of friction
In chemistry, work = pressure volume work, expansion and compression of gases

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12
Q

State the first law of thermodynamics

A

Law of conservation of energy = energy can be converted from one form to another but can neither be created or destroyed

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13
Q

State the law of conservation of matter

A

Mass is neither created or destroyed in a chemical reaction

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14
Q

What is the equation for the energy of a system

A

ΔE = q + w

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15
Q

What is an exothermic reaction

A

Release heat energy to the surroundings

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16
Q

What is an endothermic reaction

A

Absorb heat energy from the surroundings

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17
Q

Describe the signs of ΔE, q and W for different types of reactions

A

Exothermic = ΔE < 0 & q = -
Endothermic = ΔE > 0 & q = +
Work done by system (expanding/losing energy) =
w = -
Work done on system (compressed/gaining energy) =
w = +

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18
Q

Whats the equation for work

A

w = -pΔv

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19
Q

What is the ideal gas law equation

A
pv = nRT
pΔv = ΔnRT
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20
Q

What is a state function

A

Property that depends on the current state of function (E, p, v) and is independent of the path taken to reach current state

21
Q

What is a path function

A

Work and heat depend on a specific pathway

22
Q

What is enthalpy

A

A defined state function as the sum of all internal energy of a system and the product of its pressure and volume (under constant pressure)

23
Q

State the equation for enthalpy

A
H = E + pv 
ΔH = E + pΔv 
ΔH = Qp
24
Q

When does ΔH ≈ ΔE

A

At constant pressure

25
Q

State Avogadros law

A

Volume of ideal gas is directly proportional to the number of moles of gas

26
Q

What is an extensive property

A

Depends on the amount of substance (energy & enthalpy)

27
Q

What is an intensive property

A

Does not depend on amount of substance (temperature)

28
Q

What is a heat capacity

A

Amount of heat required to raise the temperature of the substance by one degree

29
Q

What is q equal to

A
q = Cs x m x Δt
q = Cn x n x Δt
30
Q

What is thermal equilibrium

A

In a system where no energy is exchanged with surroundings q1 + q2 + q3 + … + qn = 0

31
Q

What is calorimetry

A

Science of measuring heat (heat of reactions being determined experimentally)

32
Q

What is the equation for coffee-cup calorimetry

A

ΔH = Qp (constant pressure )

33
Q

What is the equation for bomb calorimetry

A

ΔE = Qv (constant volume)

34
Q

What enthalpy occurs at a melting point

A

Enthalpy of fusion

Qfus = nΔHfus

35
Q

What enthalpy occurs at a boiling point

A

Enthalpy of vaporization

Qvap = nΔHvap

36
Q

What type of reactions are melting and boiling

A

Endothermic

Qphasechange = nΔHphasechange

37
Q

What type of reactions are freezing and condensation

A

Exothermic

Qphasechange = -nΔHphasechange

38
Q

What is hess’s law

A

Change in enthalpy is the same whether the reaction takes place in one step or series of steps

39
Q

Describe the characteristics of hess’s law

A

Enthalpies can be added
Reaction reversed = sign of ΔH is flipped
Reaction is multiplied = multiply ΔH by the same

40
Q

What is standard enthalpy of formation

A

The change in enthalpy associated with the formation of one mole of a compound from its elements with all substances in their standard states
ΔH*f

41
Q

What are the standard states

A
Compounds = 
gases = 1 atm
condensed states = pure liquid or solid 
solutions = concentration of 1 M 
Elements = 
1 atm and 25*C 
ΔH*f of elements in their standard state = 0 
**DIATOMIC STATES
42
Q

What is the equation for standard Enthalpy of formation

A

ΔHrxn = Σ nΔHf (products) - Σ nΔH*f (reactants)

43
Q

State the relationship of bond energy in an exothermic reaction

A

Potential energy of the products is lower than potential energy of reactants

44
Q

State the relationship of bond energy in an endothermic reaction

A

Potential energy of the products is higher than potential energy of the reactants

45
Q

What do bond energies represent

A

The amount of energy required to break 1 mole of bond (always positive)

46
Q

What is the relationship between a bond length and its strength

A

Inverse relationship (stronger bonds = more pull so less length)

47
Q

Describe stronger bonds

A

Lower in potential energy (more stable) than weaker bonds

48
Q

What is the formula for bond strength calculations

A

ΔH = Σ n x D (bonds broken = reactants) - ΔH = Σ n x D (bonds formed = products)