PAG 3.1 determination the enthalpy change of neutralisation

Question 1

method

Answer 1

1) place polystyrene cup in a 250 cm3 beaker
2) add 25 cm3 of HCl into the cup
3) measure out 25cm3 of sodium hydroxide
4) start timer and record temperature of acid with a thermometer at 0,1,2,3 mins
5) at the 4th minute add the sodium hydroxide
6) measure the temperature of the solution and stir at 5,6,7,8,9,10 minutes

Question 2

why must the experimental value of the enthalpy of neutralisation be negative?

Answer 2

because it is an exothermic reaction as the temperature is increasing due to energy being transferred to the surroundings

Question 3

suggest a possible improvement to the method

Answer 3

add a lid to the polystyrene cup

Question 4

why would the enthalpy change be the same regardless of which strong acid or alkali is used?

Answer 4

only the hydrogen and hydroxide ions are involved

Question 5

why can the products be safely disposed of down the sink?

Answer 5

only sodium chloride and water are made

Question 6

describe whether using graphical extrapolation is more or less important for highly exothermic reactions

Answer 6

more important because more heat energy is lost at the point of the reaction so measuring the temperature difference would underestimate the temperature difference significantly