Investigate the heat of neutralisation when an acid and an alkali (a soluble base) are reacted together.

Authors Avatar

Fezan Shakir        10HM


I intend to carry out an experiment to investigate the heat of neutralisation when an acid and an alkali (a soluble base) are reacted together. I will be using strong acids, dibasic strong acids, weak acids, strong alkalis and weak alkalis to gain a wide variety of results.

Scientific Knowledge

Acids contain H+ ions. Alkalis contain OH- ions; an alkali is a soluble base. When a acid and a alkali are mixed together the H+ and OH- attract and bond together to form H2O (water). On the PH scale acids are 1-6, lower the number the stronger the acid. Alkalis are 8-14, larger the number the stronger the alkali. Neutral is 7, this is when a solution is neither acidic nor alkaline, and water is an example. Vinegar and lemon juice are acidic, kitchen cleaners are alkaline.

Equation:        Acid + Alkali                    Salt + Water

If a solution has more H+ ions it is more acidic. Therefore it has a lower PH number. In a strong acid it is mostly split up into H+ ions. So in a weak acid it only has some H+ ions.

If a solution has more OH- ions it is more alkaline. Therefore it has a higher PH number. In a strong alkali it is mostly split up into OH- ions. In a weak alkali it only has some OH- ions.

Neutralisation is exothermic. Bonds are formed when H+ and OH- ions attract, giving out heat energy. Breaking bonds require energy so is endothermic. Neutralisation happens when all the H+ and OH- ions are turned into water.


I will carry out the experiment as follows:

  1. I measured 50cm3 of the desired alkali into a conical flask.
  2. Then placed the alkali in a polythene cup.
  3. The polythene cup was then placed inside a beaker, in case if the cup leaked it wouldn’t spill all over the bench.
  4. I then measured 10cm3 of acid using a measuring cylinder.
  5. I poured the acid in the cup and measured the temperature.
  6. I do the exact same thing as in step 5 until I have added 90cm3 of acid, measuring the temperature each time.
  7. I did the exact same method for all the combinations of acids and alkalis I chose.


  • I wore goggles during the experiment to avoid the solutions making contact with my eyes.
  • I placed the apparatus in the middle of the bench to avoid anything being dropped.
  • If a substance were spilled I would immediately clean it up so that it wouldn’t be a hazard for other people.

Fair Test

  • All solutions were 2 molar.
  • I will rinse the measuring cylinder, conical flask and beakers with the solution going to be poured into them to avoid the dilution of the acid or alkali, which could affect my results.
  • I will use the same thermometer because another one may be inaccurate.
  • I shall swirl the acids and alkalis when being mixed so that it mixes up and reacts.
  • All of the experiments being done at room temperature.
  • Measuring cylinder accurate to 0.5. Thermometer accurate to 0.1°C.


I predict that when a strong acid and a strong alkali are mixed it will give out a lot of heat, depending on there strengths.

If a dibasic acid and a strong alkali are mixed I think that the amount of heat given off will be very high.

Join now!

I reckon that when a weak acid and weak alkali are added they’ll have a lower amount of heat given out than if two strong solutions were added.

When a weak acid and strong alkali react and vice versa the amount of heat given off will be lower than if a strong solutions were mixed depending on the weak solutions strength.


Hydrochloric Acid (Strong) + Potassium Hydroxide (Strong)

Sulphuric Acid (Dibasic) + Sodium Hydroxide (Strong)

Ethanoic Acid (Weak) + Ammonia (Weak)

Ethanoic Acid (Weak) + Sodium Hydroxide (Strong)


This is a preview of the whole essay