A 50.0 g-sample of acid takes 46.4 mL of 0.500 M NaOH solution to neutralize it. Assume the same amount of heat is given off as in Example 5.6.

(a) Calculate the enthalpy change for the neutralization per mole of hydrogen ions, described by the equation

(b) Is the neutralization reaction an endothermic or exothermic process?

Strategy

The thermochemical equation in (a) is for one mole of each reactant. We need to find the number of moles of acid reacted in the titration information given, using a mole-mole calculation. Dividing the total heat by the total moles of acid will give the heat energy per mole of acid. The direction of temperature change (up or down) will indicate whether the reaction is exothermic or endothermic.

Example 5.6.

A 50.0-g sample of a dilute acid solution is added to 50.0 g of a base solution in a coffee-cup calorimeter. The temperature of the liquid increases from 18.20 °C to 21.30 °C . Calculate q for the neutralization reaction, assuming that the specific heat of the solution is the same as that of water (4.184 J/g · °C).

Transcribed Image Text:

H+(aq) + OH (aq) → HO(0) ΔΗ = ?