Thermochemistry and Rates of Reaction

Question 1

Standard thermodynamic conditions

Answer 1

298K and 101 Pa

Or 25 degrees Celsius and 1 atm

Question 2

First law of thermodynamics (law of conservation of energy)

Answer 2

Energy is not created or destroyed, it is absorbed or released to surroundings

Question 3

Energy absorbed in an…

Answer 3

Endothermic reaction

Question 4

Energy released to surroundings in an…

Answer 4

Exothermic reaction

Question 5

Hess’ law

Answer 5

The standard enthalpy change for a reaction is independent of the route taken from the reactants to the products.

Question 6

Overall, energy change of reaction will be..

Answer 6

The same

Question 7

Energy cycle equation

Answer 7

Delta H1= delta H2 + delta H3

Question 8

When forming bonds releases more energy than energy to break bonds, reaction is

Answer 8

Exothermic

Question 9

When energy required to break bonds is higher than energy released, reaction is

Answer 9

Endothermic

Question 10

Enthalpy change (J) equation

Answer 10

Delta H= - mcdeltaT divide by n

Enthalpy change = - mass x 4.18 x temp change divide by number of moles

Question 11

Bomb calorimeter

Answer 11

Perfectly insulated, volume of system is kept constant

Work done calculated to give accurate enthalpy change

Question 12

Rate of reaction definition

Answer 12

Speed at which reactants are converted into products during a chemical reaction

Question 13

Rate of reaction affected by

Answer 13

Surface area of reactant
Concentration of reactant/pressure of gas
Temperature of reaction
Catalyst
Certain frequencies of light

Question 14

6 ways to measure rate of reaction

Answer 14

Measure pH using pH meter
Measure change in mass of whole reaction mixture
Evolution of a gas (change in volume/pressure)
Production of a precipitate
Change colour/colour intensity using Calorimeter
Sampling (titration a sample periodically to find concentration)

Question 15

Rate equation

Answer 15

Change in concentration over time

Question 16

Enthalpy change formation

Answer 16

Energy of reactants - energy of products

Forwards - backwards

Question 17

Heterogenous catalyst

Answer 17

Catalyst in a different state to reactant

E.g Haber process reactants all gases but catalyst is iron

Question 18

Homogenous catalyst

Answer 18

Catalyst in same state as reactants

E.g halogenation of Benzene with catalyst iron III chloride

Question 19

Why new efficient catalysts in terms of ‘industrial processes’ and ‘green chemistry’

Answer 19

Catalysts speed up reaction, activation energy lowered, less heat energy needed, less fossil fuels needed to provide heat for reaction
Less money spent on high temperatures and pressures
Less greenhouse gases produced