PAG 3 Enthalpy determination Flashcards
outline how to find enthalpy of a reaction
pour water into a beaker using a measuring cylinder and record the water added
record the initial temperature of the water using a thermometer
add methanol to a spirit burner and weigh the burner
light the burner and heat the beaker using the spirit burner
after 3 mins blow out the spirit burner
record the final temperature of the water
record the final mass of the spirit burner
diagram for enthalpy determination
why may the value for enthalpy of combustion calculated be LESS EXOTHERMIC than the recorded values?
non standard conditions
incomplete combustion
heat loss to surroundings
evaporation of methanol from wick
how could the practical be modified to obtain a more accurate value for enthalpy of combustion?
use a draught screen to prevent heat loss
insulate the beaker to prevent heat loss
burn the chemical in oxygen to ensure complete combustion
why may the value for enthalpy of combustion calculated be MORE EXOTHERMIC than the recorded values?
smaller moles were calculated which means a larger enthalpy change of combustion was calculated
why is it not possible to measure the enthalpy change of formation for a hydrocarbon directly?
the reaction of hydrogen and carbon leads to the production of many different hydrocarbons
hydrogen and carbon cannot react in standard conditions
what happens if you double the temperature in an enthalpy determination practical?
