Energy transfer in reactions, measuring enthalpy change

• what are examples of an exothermic reaction ?

  Combustion, neutralisation
• what is an exothermic reaction ?

  A reaction that releases heat to surroundings
• what is an endothermic reaction ?

  A reaction that takes in energy from surroundings
• what are examples of endothermic reactions ?

  photosynthesis and thermal decomposition
• what is the name of the overall change in energy of a reaction called?

  enthalpy change
• what is the symbol for enthalpy change ?

  ΔH
• what are the units ofΔH ?


  KJ/mol
• if the reaction is exothermic, the value is negative because the reaction is giving out energy
• if the reaction is endothermic the value is positive because the reaction takes in energy
• what is calorimetry ?

  a set of equipment allowing you to measure the amount of energy transferred in a chemical reaction
• what is this experiment called ?

  calorimetry

  
• why do we use a polystyrene cup in calorimetry?

  A) because it is a good insulator and will not absorb heat

  
• what does calotimetry help you find the enthalpy change of ?

  dissolving, displacement, neutralisation and combustion
• equation for calculating heat energy transferred ?

  Q = mcΔT
• what does m stand for in the heat energy transferred equation ?

  mass of liquid being heated
• what does the Q stand for in the heat energy transferred equation ?

  heat energy transferred
• what does the c stand for in the heat energy transferred equation ?

  specific heat capacity
• what does the ΔT mean in the heat energy transferred equation ?

  Change in temperature of liquid
• what is waters specific heat capacity ?

  4.2
• describe the steps for combustion calorimetry

  A) put water into copper can

  B) record temperature of water

  C) weigh spirit burner and lid

  D) heat water stirring untill it gets to 50C

  E) put out flame and measure final temperature of water

  F) weigh spirit burner and lid again

  G) calculate enthalpy change with results

  
• how to calculate the molar enthalpy change ?

  1. calculate heat energy change
  2. find how many moles of fuel produced this energy change
  3. then do enthalpy change over number of moles
• label this reaction profile

  A) exothermic reaction

  B) reactants

  C) products

  D) enthalpy

  E) progress of reaction

  F) ΔH = -ve

  
• label this reaction profile

  A) endothermic reaction

  B) reactants

  C) products

  D) enthalpy

  E) progress of reaction

  F) ΔH = +ve