are equal. If there were more hydrogen ions than hydroxide ions then once every hydroxide ion joined with 1 hydrogen ion there would be hydrogen ions left meaning the solution would become acidic. If there were more hydroxide ions than hydrogen ions then once every hydrogen ion joined with 1 hydroxide ion there would be hydroxide ions left meaning the solution would become alkaline. When an acid contains more hydrogen then there are a greater number of hydrogen ions per ml than in an acid containing less hydrogen so it will be stronger. For example in sulphuric acid (H2SO4) there would be more hydrogen ions than in the same amount of hydrochloric acid (HCl), twice as many because there are twice as many in the formula. The alkali in my experiment remained the same throughout (NaOH) sodium hydroxide. The acids containing more hydrogen needed smaller amounts to neutralise the alkali because they contained more hydrogen ions. If an amount of acid containing more hydrogen, equal to the amount of acid containing less hydrogen that was needed to neutralise the alkali, was added to the alkali the solution would not be neutralised it would be acidic. This is because there would be more hydrogen ions in the acid containing more hydrogen. If that amount of acid containing less hydrogen was needed to neutralise the alkali, the amounts of hydrogen and hydroxide ions must have been equal. Therefore if the same amount of an acid containing more hydrogen ions was used, the amount of hydrogen and hydroxide ions would not be equal and the solution would not be neutralised. If the amount of the acid was reduced then there would be less hydrogen ions, and if it was reduced by enough then the amount of hydrogen and hydroxide ions would be equal. That is why the larger the amount of hydrogen in the acid, the smaller the amount of acid needed to neutralise the alkali. The hydrochloric and sulphuric acids support my original predictions. I predicted that approximately 10ml of hydrochloric acid would be needed to neutralise the 10ml of sodium hydroxide. The average was 9.96ml which is very close to that amount. I also predicted that 5ml of sulphuric acid would be needed to neutralise the 10ml of sodium hydroxide. The average was 4.7ml which is quite close to the amount I predicted. However, the phosphoric acid did not support my prediction, I predicted that 3.3ml of the acid would be needed, but 6.26ml was actually needed to neutralise 10ml of sodium hydroxide. This is because of its rate of dissociation. When the acid is dissolved in water to make a solution, it donates some of its hydrogen atoms to the solution where they become hydrogen ions. How many of its hydrogen atoms the acid donates is its rate of dissociation. Hydrochloric and sulphuric acid have nearly 100% rate of dissociation, meaning that they donate almost all of their hydrogen. Phosphoric acid only has roughly a 50% rate of dissociation, meaning that it donates only about half of its hydrogen. This means it only has about half the ability to neutralise as you would expect, which is why it took almost twice the amount I predicted to neutralise the alkali.
Here's what a teacher thought of this essay
This is a very good experiment analysis, a little repetitive, but the Science is sound, showing a good understanding. All the necessary elements are present to award a high grade. 4 stars.