Energetics

Question 1

Exothermic and Endothermic

Answer 1

Mexo - Heat energy given out (more energy released from making bonds than breaking bonds)
Bendo - Heat energy taken in (more energy taken in to break bonds than making bonds)

Question 2

Displacement reaction (Calorimetry)
Magnesium displacing copper from copper(II) sulfate
Why polystyrene?

Answer 2

Mg (s) + CuSO4 (aq) -> MgSO4 (aq) + Cu (s)
50cm^3(50g) copper sulfate in polystyrene cup
Record initial temp of solution
Add magnesium (then cover lid)
Record final temp of solution
Polystyrene because it is an insulator which reduces heat loss, more accurate results

Question 3

Combustion reaction (Calorimetry)
Ethanol is burnt in a small spirit burner

Answer 3

C2H5OH + 3O2 -> 2CO2 + 3H2O
Measure initial mass of spirit burner (including ethanol)
100cm^3 water into copper container, measure initial temp of water with thermometer inside
Light burner until temp rises by 30°C
Extinguish flame, measure final temp of water
Measure final mass of spirit burner (initial - final = mass of ethanol burnt)

Question 4

Equation to calculate heat energy transferred in calorimetry experiment

Answer 4

Q (J) = m (g) x c x DT (°C)

Heat gained/lost = mass of solution x heat capacity of solution x change in temp