Exothermic and endothermic reactions and calorimetryIB MYP Chemistry: Mind map

Exam questions on Exothermic and endothermic reactions and calorimetry

1. A hiker in Chile carries a disposable hand warmer. When she opens the sachet, the iron powder inside reacts with oxygen from the air and the sachet warms to about 55 °C for several hours. Her friend carries an instant cold pack for sports injuries. When the pack is squeezed, a solid dissolves in water inside it and the pack quickly becomes cold.
   Explain, in terms of energy transfer, why the hand warmer feels warm but the cold pack feels cold.2 marks
2. A student in Kuala Lumpur burns ethanol in a spirit burner to heat 100 g of water in a metal can. The temperature of the water rises from 20.0 °C to 52.0 °C. The mass of the spirit burner falls from 85.40 g to 84.65 g. The specific heat capacity of water is 4.18 J/g/°C.
   Calculate the energy transferred to the water, in joules.2 marks
3. Students at a school in Lagos compare two liquid fuels, ethanol and propan-1-ol, to find which releases more energy per gram. They burn each fuel in a spirit burner to heat 100 g of water in a metal can. Burning 0.80 g of ethanol raises the temperature of the water by 30.0 °C. Burning 0.70 g of propan-1-ol raises the temperature of the water by 33.0 °C. The specific heat capacity of water is 4.18 J/g/°C. The data book value for propan-1-ol is 33.6 kJ/g.
   State two variables that the students should control to make the comparison fair, and one safety precaution they should take.3 marks