CHEMICAL ENERGETICS

Question 1

What are the standard conditions?

Answer 1

298K and 1 bar(10 to the power of 5)

Question 2

What is the formula to find heat change

Answer 2

mc(delta T) or Vc(delta T)

Question 3

What is Hess’ Law

Answer 3

Hess law states that the enthalpy changes in a chemical reaction is independent on the pathway which the reaction take place provided that the initial and final states of the system are constant

Question 4

enthalpy change of combustion

Answer 4

heat change when one mol of substance is completely burnt in excess oxygen under standard conditions

Question 5

formation?

Answer 5

heat change when one mol of a substance is formed from its elements in their standard states under standard conditions

Question 6

neutralisation

Answer 6

heat change when one mol of water is formed when an acid neutralizes a base and is carried out in an infinitely dilue aq solution under SC

Question 7

BE?

Answer 7

Heat cahngge when one mol of any C bond between two atoms in a gaseous molecule are broken

Question 8

LE

Answer 8

heat change when one mol of ionic solid is formed from its gaseous ions under SC

Question 9

atomisation

Answer 9

heat change when one mol of isolated gaseous atoms are produced from the element in the standard state under SC

Question 10

electron affinity?

Answer 10

heat change when one mol of gaseous atoms or negatively charged ions gains an electron

Question 11

hydration?

Answer 11

heat change when one mol of gaseous ions are dissolved in a large amt of water under SC

Question 12

solution?

Answer 12

heat change when one mol of solute is completely dissolved in a solvent to form an infinitely dilute solution under SC

Question 13

What other calc formulae are there?

Answer 13

BE of reactants - BE of products
Hc of reactants - Hc of products
Hf of products - Hf of reactants
H(sol)=H(LE) - H(hyd)

Question 14

What affects affect entropy?

Answer 14

1. Change in temp can increase the disorder. Ke of molecules increase which causes the Boltzmann E distribution curve to broaden as there are more ways to arrange the energy quanta in the hotter species
2. Change is Phase
3. Change in umber of particles which affects number of ways to arrange particles
4. Mixing of particles causes higher state of disorder

Question 15

Gibbs free energy formulae. What does it tell you about the reaction?

Answer 15

enthalpy change - T( entropy change)
if its smaller than 0 it is spontaneous if at 0 it is at equilibrium