core practical 8: enthalpy change using hess law

Question 1

calorimetry

Answer 1

• poylstyrene cup in beaker = support and insulation
• measure first solution in volumetric pipette and then add
• CLAMP thermometer in place
• measure initial temp ever 30 seconds for 2-3 mins
• at 3 mins, add second reagent and STIR
• record temp after waiting a min every 30 seconds

Question 2

method for processing

Answer 2

• if reaction is slow, exact temperature rise difficult to obtain as cooling occurs
• so take ergular reafings and EXTRAPOLATE curve to time when reactants were added together

Question 3

errors

Answer 3

• heat loss to surroundings
• assumed all so;utions have shc of water
• ## shc calorimeter ignored

Question 4

what mass do you use to be the mass

Answer 4

solutions

Question 5

why cant you measure enthapy change of anhydrous to hydrated salt

Answer 5

• difficult to measure temperature change of a solid
• impossible to add exact amount of water without solid dissolving

Question 6

errors with flame calorimetry

Answer 6

• heat loss to surroundings
• incomplete combustion of fuel
• ## evaporaton of FUEL