Energy I

Question 1

Activation energy

Answer 1

minimum energy required for a reaction to occur

Question 2

exothermic

Answer 2

more energy released in the formation of bonds than is absorbed in bond breaking

Question 3

enthalpy (H)

Answer 3

the heat content of reactions

Question 4

enthalpy change of combustion

Answer 4

the enthalpy change that occurs when one mole of a substance reacts completely with oxygen under standard conditions with all reactants and products in their standard states

Question 5

standard conditions

Answer 5

298K, 100kPa, 1moldm-3

Question 6

enthalpy change of reaction

Answer 6

enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation

Question 7

enthalpy change of formation

Answer 7

enthalpy change that occurs when one mole of a compound is formed from its elements under standard conditions

Question 8

average bond enthalpy

Answer 8

the average energy needed for 1 mole of a given type of gaseous bond to undergo homolytic fission in a gaseous molecule

Question 9

q=mcΔT

Answer 9

heat released into and absorbed from surroundings = mass of water * specific heat capacity of water * change in temperature

q is measured in J

Question 10

ΔH =

Answer 10

q / mol

Question 11

Hess’ law for ΔcH

Answer 11

reactants- products

Question 12

Hess’ law for ΔfH

Answer 12

products- reactants

Question 13

homogenous equilibrium

Answer 13

all reactants and products in the same states

Question 14

heterogenous equilibrium

Answer 14

• reactants and products in different states
• only include gaseous + aqueous in the equation

Question 15

calculating equilibrium concentration

Answer 15

I nitial moles
C hange
E quilibrium
[ ] concentration

Question 16

calculating equilibrium concentration example

Answer 16

0.60 mol of H2(g) was mixed with 0.40 mol of I2(g) in a sealed container with a volume 1.0 dm3.
The mixture was allowed to reach equilibrium and it was found that 0.28 mol of H2(g) remained.

H2 + I2 <——> HI
I 0.60 0.40 0
C -0.32 -0.32 +0.64
E 0.28 0.08 0.64
[] 0.28 0.08 0.64

Question 17

Kc (equilibrium constant) =

Answer 17

[ products ] / [reactants]
If:
4A + 5B <—–> 4C + 5D
then Kc =
([C]⁴ * [D]⁵) / ([A]⁴ * [D]⁵)

Question 18

position of equilibrium

Answer 18

the extent of the forwards and backwards reaction

Question 19

the value of Kc indicates….

Answer 19

the position of equilibrium,
if Kc> 1 then equilibrium lies to the right as products>reactants