C5 Chemical Energetics

Question 1

standard conditions

Answer 1

298K, 101kPa (1atm), symbol ⦵

Question 2

enthalpy change of reaction

Answer 2

enthalpy change when the amount of reactants shown in the equation react together to give products under standard conditions

Question 3

enthalpy change of formation

Answer 3

enthalpy change when 1 mol of compound is formed from its constituent elements in their standard states

Question 4

Hf values for ELEMENTS

Answer 4

0

Question 5

enthalpy change of combustion

Answer 5

enthalpy change when 1 mol of substance is burned in an excess of oxygen under standard conditions

Question 6

product of complete combustion

Answer 6

CO2, H2O, SO2

Question 7

enthalpy change of neutralisation

Answer 7

enthalpy change when 1 mol of water is formed from an aqueous acid and aqueous alkali

Question 8

why is enthalpy change of neutralisation less for weak acid than strong acid?

Answer 8

Additional energy is absorbed to fully ionise weak acid

Question 9

enthalpy change formula

Answer 9

q = -mcT

m = total mass of WATER/SOLUTION (g)
c = 4.18
T = C/K

Question 10

enthalpy change of neutralisation formula

Answer 10

Enthalpy change, q/moles of water formed

Question 11

enthalpy change of combustion fomula

Answer 11

enthalpy change, q/moles of substance combusted

Question 12

bond energy

Answer 12

energy needed to break one mole of covalent bonds in the gaseous state

(ensure all reactants and products are in GASEOUS FORM when calculating)