3.1 Enthalpy change of neutralisation

HCl(aq) + NaOH(aq) ——> NaCl(aq) + H₂O(l)

How should you setup the apparatus?

Put a thermometer into a polystyrene cup (not touching edges) which is in a beaker.

What ratio of reactants should you put into the polystyrene cup?

1:1 - e.g. 25cm³ of the acid and alkali. The ratio depends on the equation, as the equation must produce 1 mole of water.

What is the uncertainty of a thermometer?

O.5⁰C

After how long should you add the sodium hydroxide?

4 minutes

(Before just measuring temp of HCl)

How often should you take recordings of the temperature?

Every minute - except for 4th, as this is when Na(OH)₂ is added

For 10 min

When plotting on a graph, what is on the x and y axis?

X = time(m)

Y = temperature(⁰C)

What do you do with the graph?

Draw line of best fit between points at 0,1,2 and 3 minutes and a separate one from 5 and onwards - extrapolate back to 4 min.

Calculate temp rise at 4 min

What do you do after calculating temp rise at 4 min?

Use equation q=mcΔT to calculate energy absorbed (q)

REMEMBER ==> convert to KJ

If not given, assume density = 1g/cm³, and specific heat capacity is same as water, 4.18J/(gK)

What do you do after calculating energy absorbed?

Calculate the moles of HCl used

How do you calculate the enthalpy change of neutralisation?

divide energy absorbed(KJ) by the amount of HCl (moles)