gen chem II exam 1

Thermodynamics

The science of the relationship between heat & other forms of energy

Thermochemistry

an area of thermodynamics that concerns the study of heat absorbed or evolved by a chemical reaction

Evolution

Making / releasing heat

Absorption

Needing/ taking in heat

Energy

A property of matter that explains the potential/ capacity to move matter

Converted

One form of energy can be _______ to another form of every

Electromagnetic, mechanical, electrical, chemical

What are the types of energy?

Kinetic energy (Ek)

The energy associated with an object by virtue of its motion

½ m(v2)

Ek=?

m /s

What is the si unit for velocity?

Joules (J)

What is the si unit for energy?

Kg(m2)/s2

J=?

Calorie (cal)

the non - si unit for energy that describes the amount of energy required to raise the temp. of one gram of water by one degree Celsius

4.184 J

1 cal =?

Potential energy

The energy an object has by virtue of its position in a field of forces such as gravitational, electric, or magnetic field

Gravitational potential energy

Given by Ep

mgh

Ep=?

Gravitational constant ( 9.8 m/s 2)

g =

Internal energy (u)

The sum of the kinetic & potential energies of the particles making up a substance

Etot + Ek + Ep + u

Total energy =?

Law of conservation of energy

Energy may be converted from one form of energy to another but the total quantity of energy remains constant

Thermodynamic system/ system

The substance under study in which a change occurs.

Thermodynamic surroundings

Everything else in the vicinity ( not a part of the system)

Heat

Evolution, or reactions that make/release heat, are great sources of _______.

The cold

Absorption, or reactions that take in heat, are sources of ______.

The mass & speed of an object

What is kinetic energy dependent on?

Heat(q)

Energy that flows in or out of a system because of a difference in temperature between the thermodynamic system & its surroundings

Spontaneously from a region of higher temperature to a region of lower temperature

How does heat flow?

Steam being exerted from tea to the area around it

What is an example of heat flowing?

Positive

The value of q is _ when heat is absorbed by a system

Negative

The value of q is __ when heat is evolved by a system

Heat of reaction

Value of q required to return a system to the given temperature at the completion of the rxn at a given process

Endothermic process

Chemical reaction or process in which heat is absorbed by the system

Positive

Is q positive or negative for an endothermic process?

Exothermic process

Chemical reaction or process in which heat is evolved by the system

Negative

Is the value of q negative or positive for an exothemic process?

Enthalpy (H)

Extensive property of a substance that can be used to obtain the heat absorbed or evolved in a chemical reaction

Extensive property

Property that depends on the amount of substance like Mass or volume

State function

Property of a system that depends only on its present state and is independent of any previous history of the system

Certain variables like temperature & pressure

What is a substances present state determined by?

Enthalpy of reaction

Change in enthalpy for a reaction at a given temperature & pressure

Hproducts - H reactants

Delta H=?

The heat of reaction at constant pressure (q p)

What else is enthalpy change = to?

Delta H= delta U + P (delta V)

What is a precise definition of enthalpy?

-P(delta V) + delta H

Delta U=?

Pressure - volume work (-p delta v).

The energy needed to change volume against atmospheric pressure

Thermochemical equation

Chemical equation for a reaction (including phase labels) and enthalpy of reaction is written directly after the equation

1. If equation is multiplied by a factor, then delta H must be multiplied by same factor

2. When equation is reversed, the sign on enthalpy is also reversed

What are the rules for manipulating the thermochemical equation?

First look at the heat needed to raise the temperature of a substance because that is the basis of measurements of heat of reaction

What are the steps to measuring the heat of a reaction?

Heat capacity ( c )

The quantity of heat needed to raise the temperature of the sample by one degree Celsius or Kelvin

Molar Heat Capacity

The heat capacity of one mole of substance

Specific Heat capacity (s). / specific heat

The quantity of heat needed to raise the temperature of one gram of substance by one degree Celsius or Kelvin at a constant pressure

Q= c(delta t)

When using heat capacity, what equation is suitable to find heat?

Q = s x m x delta t

When using specific heat capacity, what equation is suitable to find heat?

Calorimeter

A device used to measure the heat absorbed or evolved during a physical or chemical change

Work ( w)

An energy transfer in/out of a system whose effect on the surroundings is equivalent to moving an object through a field of force

W=+

When work is done on the system

W=-

When work is done by the system

When heat is equal between the system & surroundings

The heat flow stops

System contracts

Pressure - volume work is done on system

When system expands

Pressure- volume work is done by system

Pressure volume work (w)

-p( delta v. )

Hess ‘s law of heat summation

For a chemical equation that can be written as a sum of 2 or more steps, the enthalpy change for the overall equation equals the sum of the enthalpy changes of the individual steps

Standard state

Standard thermodynamic.conditions chosen for substances when listing / comparing thermodynamic data

1 ATM,& 25 degrees Celsius

Typical standard conditions

A degree sign

Standard conditions are indicated with

Standard enthalpy of reaction

The enthalpy of a reaction whose products & reactants are in the standard State

Allotropes

Different form of an element in the same physical state

Carbon as a solid can be a diamond or graphite

Example of allotrope

Reference form

The most stable form of an element in regards to both its physical state & allotrope

Standard enthalpy of formation

The change in enthalpy for the formation of I mol of the substance from its elements in reference form & standard state

Zero

Standard enthalpy of formation for an element in both its reference form & standard state

First law of thermodynamics

The law of conservation of energy applied to a thermodynamic system ; delta u =q + w

Heat( q) & work(w)

The types of energy exchanged between a system & its surroundings

Heat (q) = negative

When heat is evolved by the system

Decreases internal energy of the system

When heat is negative

Heat (q) = positive

When heat is absorbed by the system

Increases internal energy of system

When heat is positive

Work (w) = negative

When system expands / delta V increases

Decreases internal energy

When work is negative

Work = +

When system contracts / delta V -

When work = positive

Increases internal energy

Surroundings do work on system

When work is positive

System does work on surroundings

When work is negative

Fuel

Any substance that is burned or similarly reacted to provide heat or other forms of energy

1. Supply substances for the growth & repair of tissue

2. Supply substances for the synthesis of compounds used in bodily regulation

3. Supply energy

Three needs of the body that food fills:

Spontaneous process

A physical or chemical change that occurs all by itself

Spontaneous process

Does not require force & continues until equilibrium is reached

Rock rolling down a hill

What is an example of a spontaneous process?

Nonspontaneous process

A physical or chemical change that does require outside force

Rock being pushed up a hill

What is an example of a nonspontaneous process?

Entropy (S)

Thermodynamic quantity that is a measure of how dispersed the energy of the system is among the different possible ways that the system can contain energy

When heat from tea spreads to mug, hands, air

What is an example of entropy increasing?

Yes

Is entropy a state function?

Yes

Is entropy an extensive property?

J/K

What is the units of entropy?

Second law of thermodynamics

The total entropy of a system & surroundings always increases for a spontaneous process

No, it is a measure of the spread of energy

Is entropy a measure of energy ?

For spontaneous process at a constant temperature

Delta S = entropy created + q/t

For spontaneous process

Delta S >q/t