physical chemistry

Question 1

formula for enthalpy change (ΔH)

Answer 1

enthalpy change = heat energy change/mols

ΔH = q/n

Question 2

formula for mols (n)

Answer 2

mols = mass/molar mass (relative formula mass)

n = m/Mr

Question 3

formula for enthalpy change using bond energies

Answer 3

energy in - energy out

energy in (reactants added together)
energy out (products added together

Question 4

exothermic

Answer 4

transfers energy to the surroundings so the temperature of the surroundings increases

Question 5

endothermic

Answer 5

transfers energy to take in the surroundings so the temperature of the surroundings decreases

Question 6

rate of reaction

Answer 6

amount of reactant used/time

amount of product formed/time

Question 7

energy supplied by water

Answer 7

energy supplied by water = mass of water x specific heat capacity x change of temperature in water

Question 8

factors that effect the rate of reaction

Answer 8

temperature
pressure
concentration
catalysts
surface area

Question 9

what is a catalyst and how do they work

Answer 9

catalysts are substances that speed up chemical reactions

they provide alternate pathways for a chemical reaction with lower activation energy