Student Question

How does the concentration of an acid affect the amount of heat produced when it reacts with a base?

Expert Answers

An illustration of the letter 'A' in a speech bubbles

In a neutralization reaction, you have the addition of an acid with a base.  Acids produce a hydrogen ion (H+), while bases produce a hydroxide ion (OH-).  When you add an acid to a base, you get the production of a salt plus water.  The following is a good example, where you add hydrochloric acid to sodium hydroxide:

HCl + NaOH --->  NaCl + H2O

When you talk about the concentration of the acid or the base, you are talking about the available number of hydrogen ions or hydroxide ions that exist to bond together.  There is some heat released with each union of an H+ to a OH- to produce an H2O.  The more unions you produce by increasing the concentration, the more heat is produced.  So higher concentration has a direct effect on the amount of heat produced.  If you add a strong acid in high concentration to a strong base in high concentration, expect to have a significant amount of heat generated as a result ot the reaction.

Approved by eNotes Editorial
An illustration of the letter 'A' in a speech bubbles

The heat released depends on the amount (moles or molecules) of the acid that reacts. A certain amount of heat is released for each molecule of the acid that reacts. More molecules = more heat.

So, if a solution is more concentrated, then the same volume will have a larger number of particles and will therefore give off more heat when it reacts.

See eNotes Ad-Free

Start your 48-hour free trial to get access to more than 30,000 additional guides and more than 350,000 Homework Help questions answered by our experts.

Get 48 Hours Free Access
Approved by eNotes Editorial