PAG 4.1 identifying unknowns 1

Question 1

method

Answer 1

1) place a polystyrene cup in a 250 cm3 glass beaker
2) rinse the measuring cylinder with HCl acid then measure 25cm3 of it and transfer to the polystyrene cup
3) measure 25 cm3 of sodium hydroxide
4) start your timer and record the initial temperature
5) record that temp for 1,2,3 mins
6) at 4th min don’ t record temp instead add sodium hydroxide and stir
7) continue to stir and record temp at 5,6,7,8,9, 10 mins

Question 2

explain why your experimental value must be negative

Answer 2

its an exothermic reaction because thermal energy is being transferred from the reaction to the surroundings

Question 3

why is it safe to dispose of the product down the sink?

Answer 3

its a neutralisation reaction so only water is being produced

Question 4

why is the enthalpy change of neutralisation the same no matter which acid or alkali used?

Answer 4

only hydrogen ions and hydroxide ions are used