Kinetics and enthalpy ?

Question 1

What does the area under the Maxwell- Boltzmann curve tell you ?

Answer 1

total number of molecules in the system

Question 2

Where is the median energy of particles?

Answer 2

Can be seen directly below the peak of the curve

Question 3

Where is the mean energy of the particles ?

Answer 3

slightly to the right of the peak . particles at very high energies skew mean to the right ( towards higher energies)

Question 4

What are the effects of increasing temperatures?

Answer 4

• molecules are moving faster so frequency of collisions increases
• number of molecules with minimum activation energy has increased substantially, so more effective collisions which result in reaction.

Question 5

What is enthalpy? Is enthalpy hard to determine ?

Answer 5

enthalpy is all the heat energy that is stored in a chemical system ie all the chemicals present in a reaction.

scientists usually use enthalpy change as enthalpy itself is tricky to determine

Question 6

enhalpy change is always determined under what conditions ?

Answer 6

• Standard conditions.
• These are 298 K which is equivalent to 25 degrees C and a pressure of 100kPa.
  -elements must also be solid, liquid or gas ( in their standard states)

Question 7

What is standard enthalpy change of combustion ?

Answer 7

it is the enthalpy change when one mole of a substance reacts completely with oxygen under standard conditions

Question 8

what is standard enthalpy change of formation ?

Answer 8

one mole of a compound is formed from its elements under standard conditions