Neutralization is a chemical reaction, also called a water forming reaction, in which an acid and a base react and produce a salt and water(H2O). In other words, it can be said that neutralization is the combination of hydrogen ions H+ and hydroxide ions OH- (or oxide ions O2-) to form water molecule H2O. In the process, a salt is formed. Most generally, the following occurs: acid + base ¡÷ salt + water

In the process of neutralization a proton (usually hydrogen) is transferred. Recall that an acid is a proton donor, while a base is a proton receiver. H2O can act as either an acid or a base, depending on whether it comes in contact with an acid or a base.

Neutralization is generally exothermic, meaning it produces heat. One example of an endothermic neutralization is that of baking soda and vinegar (or other weak acids)

Now consider the reaction between Hydrochloric acid and sodium hydroxide solutions:

hydrochloric acid + sodium hydroxide ¡÷ sodium chloride + water

HCl(aq) + NaOH(aq) ¡÷ NaCl(aq) + H2O(l)

Since the HCl and NaOH dissociate into ions in solution, the ionic equation is:

H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) ¡÷ Na+(aq) + Cl-(aq) + H2O(l)

And since the sodium and chloride ions are just spectator ions not involved in the reaction, the net equation becomes:

H+(aq) + OH-(aq) ¡÷ H2O(l) : £GrH = -55.90 kJ mol-1

Now, let's do it in the lab.
1. Open Virtual Lab Simulator and perform the following simple experiment.

2. Into an empty 250mL Erlenmeyer flask, place 50mL of 1M NaOH. Record the starting temperature (the thermometer is just above the pH meter in the lower right).

3. To this flask add 50mL of 1M HCl and carefully note the highest temperature reached on the thermometer located just above the pH meter.

Starting temperature: ____________ ¢FXC

Highest temperature: ____________ ¢FXC

4. Calculate the number of moles of both NaOH and HCl used.
# moles = ________________

5. Using the equation: q = s !N m !N ¢GGT, where q is the total amount of heat, s is the specific heat of water (4.184 J/g ¢FXC), m is the total mass of water (assume a density of 1g/mL), and ¢GGT is the difference between the readings recorded above.

6. Calculate ¢GGH (on a molar basis) for the reaction: HCl(aq) + NaOH(aq) !¡Ò NaCl(aq) + H2O(l)

Additional Ideas
¡P Try a different strong acid. Do your results change? Explain.
¡P Repeat the experiment and carefully observe the relative amounts of H + and OH as the temperature changes. Explain what you observe.