Energetics Flashcards
What is an exothermic reaction
Gives out energy
Chemical energy is released
The products have less energy than the reactants
The surroundings get hotter
How can you tell from an energy level diagram wether the reaction is exothermic or endothermic
Loss in energy = exothermic
Gain in energy = endothermic
Give some examples of endothermic reactions
Photosynthesis
Thermal decomposition
Give the equation to find out the total heat energy
Q = mc∆T
Q = Total heat energy change (Joules) m = Mass of solution c = Specific heat capacity of water (4.18J/g/°C) T = Change in temperature
Why would you use a polystyrene cup in the experiment to study heat loss
Why is it important to reduce heat loss
Good heat insulator
Also use a cardboard lid to reduce heat loss
To make the experiment more reliable
In the heat loss experiment, why wasn’t a metal container used
Bad insulator
Give the equation that you could use to work out the molar enthalpy change
Heat energy change (Q)
————————————-……………= molar enthalpy change
Amount in moles of reactants (n)
Negative sign shows heat is released and the combustion is exothermic
Explain how you would set up a calorimetry experiment
Measure 50cm water into calorimeter and record temperature of water
Select one of the spirit burners, record it’s name and the initial mass of the burner and fuel
Light the spirit burner and allow to burn. Stir the water until the temperature has risen by about 30 °C. Extinguish the burner
Record the maximum temperature of the water
Reweigh the burner contents and it’s mass
Repeat for the other fuels
How is the calorimetry experiment designed to ensure that all heat energy is transferred to water
How could the experiment be improved
Carload lid prevents heat loss swell as the cardboard boards surrounding it
More insulation
Air supply
