quiz 1 Flashcards by Misha Gandhi

What is energy

Capacity to do work or produce heat

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What are the two types of energy

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

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What makes up internal energy

E = PE + KE

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What does nature prefer

A lower energy state

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Describe thermochemistry

Deals with heat effects accompanying chemical reactions

Always a flow of heat into or out of the system

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Describe thermodynamics

Study of energy and its conversion into different forms

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What is a system

Part of universe we focus our attention on

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What is the surrounding

Everything else in the universe

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What is temperature

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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What is heat

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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What is work

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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State the first law of thermodynamics

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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State the law of conservation of matter

Mass is neither created or destroyed in a chemical reaction

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What is the equation for the energy of a system

ΔE = q + w

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What is an exothermic reaction

Release heat energy to the surroundings

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What is an endothermic reaction

Absorb heat energy from the surroundings

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

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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Whats the equation for work

w = -pΔv

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What is the ideal gas law equation

pv = nRT
pΔv = ΔnRT

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What is a state function

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

What is a path function

Work and heat depend on a specific pathway

What is enthalpy

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)

State the equation for enthalpy

H = E + pv 
ΔH = E + pΔv 
ΔH = Qp

When does ΔH ≈ ΔE

At constant pressure

State Avogadros law

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

What is an extensive property

Depends on the amount of substance (energy & enthalpy)

What is an intensive property

Does not depend on amount of substance (temperature)

What is a heat capacity

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

What is q equal to

``` q = Cs x m x Δt q = Cn x n x Δt ```

What is thermal equilibrium

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

What is calorimetry

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

What is the equation for coffee-cup calorimetry

ΔH = Qp (constant pressure )

What is the equation for bomb calorimetry

ΔE = Qv (constant volume)

What enthalpy occurs at a melting point

Enthalpy of fusion | Qfus = nΔHfus

What enthalpy occurs at a boiling point

Enthalpy of vaporization | Qvap = nΔHvap

What type of reactions are melting and boiling

Endothermic | Qphasechange = nΔHphasechange

What type of reactions are freezing and condensation

Exothermic | Qphasechange = -nΔHphasechange

What is hess's law

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

Describe the characteristics of hess's law

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

What is standard enthalpy of formation

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

What are the standard states

``` 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 ```

What is the equation for standard Enthalpy of formation

ΔH*rxn = Σ nΔH*f (products) - Σ nΔH*f (reactants)

State the relationship of bond energy in an exothermic reaction

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

State the relationship of bond energy in an endothermic reaction

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

What do bond energies represent

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

What is the relationship between a bond length and its strength

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

Describe stronger bonds

Lower in potential energy (more stable) than weaker bonds

What is the formula for bond strength calculations

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