physical chemistry - energetics

Question 1

what is an exothermic reaction

Answer 1

chemical reaction where heat is released

Question 2

what is an endothermic reaction

Answer 2

chemical reaction where heat is absorbed

Question 3

what is calorimetry

Answer 3

an experiment that allows for the measurement of the amount of energy transferred in a chemical reaction to be calculated.

Question 4

calorimetry experiment for displacement, dissolving and neutralisation reactions

Answer 4

• 50 cm3 of copper(II) sulphate is measured and transferred into a polystyrene cup.
• polystyrene is used as its and insulator of heat, which reduces heat loss.
• The initial temperature of the copper sulphate solution is measured and recorded.
• Magnesium is added and the maximum temperature is measured and recorded.
• The temperature rise is then calculated.

Question 6

what is an exothermic reaction

Answer 6

a chemical reaction that releases heat

Question 7

what is an endothermic reaction

Answer 7

a chemical reaction that absorbs heat

Question 8

what is calorimetry?

Answer 8

Calorimetry allows for the measurement of the amount of energy transferred in a chemical reaction to be calculated.

Question 9

calorimetry experiment for combustion

Answer 9

• The initial mass of the ethanol and spirit burner is measured and recorded.
• 100cm3 of water is transferred into a copper container and the initial temperature is measured and recorded.
• The burner is placed under of copper container and then lit.
• The water is stirred constantly with the thermometer until the temperature rises by, say, 30 oC
• The flame is extinguished and the maximum temperature of the water is measured and recorded.
• The burner and the remaining ethanol is reweighed

Question 10

calorimetry experiment for displacement, dissolving and neutralisation

Answer 10

• 50 cm3 of copper(II) sulphate is measured and transferred into a polystyrene cup.
• polystyrene is used as it’s an insulator which reduces heats loss
• The initial temperature of the copper sulphate solution is measured and recorded.
• Magnesium is added and the maximum temperature is measured and recorded.
• The temperature rise is then calculated.

Question 11

how to calculate energy transferred

Answer 11

Q = mcΔT

energy transferred = mass x heat capacity x temperature rise

Question 12

how to calculate molar enthalpy change

Answer 12

ΔH = Q/n

molar enthalpy = energy tranferred (Kj)/number of moles