Chapter 2 - Energy Calculations Flashcards Preview

CHEMISTRY Unit 3/4 > Chapter 2 - Energy Calculations > Flashcards

Flashcards in Chapter 2 - Energy Calculations Deck (17):

What is thermochemistry?

Study of how energy changes in a chemical reaction


What is enthalpy?

The total energy stored in a substance. We measure a change in enthalpy from reactants to products. It is measured at SLC with 1 molarity.


Exothermic delta H value

Release heat = negative


Endothermic delta H value

Absorb heat = positive


describe the Kinetic Molecular theory of gases (KMT)

-particles always in motion
-collisions are elastic
-all gases have the same average kinetic energy


What is pressure?

Pressure is force per unit of area. It describes the collision of gas molecules with the container.


conversion for pressure

760mmHg = 1 atm = 101.3 kPa


conversion for volume

1m^3 = 1,000 L
1cm^3 = 1 mL


What is the ideal gas equation?

PV = nRT

P= kPa
V= L
T= K


What value is R



How to find an equation from the ideal gas equation

1.Make everything that is constant the letter k

2. Get all the k letters on one side and everything else on the other

3. Once we have just k on one side we can use the rule as e.g: P1V1=k, therefore P1V1=P2V2


What is an energy profile diagram?

A diagram which shows the change in energy throughout the progress of a reaction


energy profile diagram EXOTHERMIC

high to low


energy profile diagram ENDOTHERMIC

low to high


describe how methane is considered both a non-renewable and renewable resource.

Depends on the source methane. When derived from fossil fuels and pockets in the earths crust it is considered non-renewable as these sources were made millions of years ago. However, when derived from biological matter and the anaerobic rotting of animals and plants it is renewable as it can be produced faster than it is used.


errors that can occur when measuring the heat of combustion of a substance

incomplete combustion - not all energy used
heat lost- into surroundings, container
impurities- in substance lead to false data


When having to rearrange equations to find an overall enthalpy what is the golden rule

We only reverse an equation if the species in question is on the wrong side of the arrow when compared to the desired equation.