3a (Energetics)

Question 1

Exothermic

Answer 1

Chemical reaction in which heat energy is given out

Question 2

Endothermic

Answer 2

chemical reaction in which heat energy is taken in

Question 3

Q =

Answer 3

mcΔT

Question 4

molar enthalpy (kg/mol) =

Answer 4

Amount of energy transfered in (KJ) / number of moles (moles)

Question 5

Displacement, dissolving and neutralisation reactions

Answer 5

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

Question 6

Combustion reactions

Answer 6

• 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.
• The amount of energy produced per gram of ethanol burnt can also be calculated