Physica Chemistry Flashcards
What is an exothermic reaction
When heat is given out
What is an endothermic reaction
When heat is taken in
Describe how calorimetry works
Use a coffee cup and add a lid, add cotton to reduce heat loss by conduction and evaporation
Add a thermometer to record temperature
Add reactants and heat
Take the temperature every 30 seconds and record the highest temperature
A positive value is endothermic as it takes in heat
What is enthalpy change
Overall change in energy
How can you calculate heat energy transferred
Mass x specific heat capacity x change in temperature
How can you perform a calorimetry investigation using combustion
Use a screen to act as a draught excluder
Put 50g of water in the can and measure its temperature
Weight the spirit burner and lid
Heat the water until 50 degrees Celsius
Put out the flame and measure the final temperature
Weigh the spirit burner and lid again
How can you find the molar enthalpy mass
Energy released/moles
When energy is released the sign is negative
How can you measure how surface area affects rate
Connect beaker to gas syringe
Record the volume of gas produced in regular time intervals
Repeat experiment using the same volume and concentration of acid
But more crunched up marble pieces
Use mass of powdered chalk
How can you measure the affects of a catalyst on rates of reaction
Use manganese oxide to speed up the decomposition of hydrogen peroxide
Oxygen gas is given off so use a gas syringe to measure the volume of gas produced in regular time intervals
Use a different catalyst next time and compare catalysts as well as their effectiveness
How can you increase rate of reaction
Increase surface area
Increase temperature
Add a catalyst
Increase the pressure
What is a reversible reaction
A reaction where the reactants can react with each other to form a product and then convert back to the original reactants
Describe how the thermal decomposition of ammonium chloride is a reversible reaction
Ammonium chloride is heated and breaks down into ammonia + hydrogen chloride (forward reaction)
As they cool they react to form ammonium chloride (backwards reaction)
