Neutralising alkali at different concentrations

Acids and alkalis all have different pH’s, this is how strong they are. pH 1 is the property of a very strong acid, and pH 14 is the property of a very strong alkali. pH 7 is neutral, a liquid that has a pH of 7 is water. In this experiment I changed the concentration of the alkali, this is how many atoms there are in a certain area.

Method

I will put the Burette into the clamp and fill it with 50cm cubed of acid. I will then put the amount of water and alkali that I need for the certain concentration into the flask. I will add three drops of universal indicator in order to see the pH change in the solution.

I will slowly let the acid out of the Burette into the flask waiting until there is a definite colour change in the liquid, when it turns clear I will mix the solution so that I can check if there is enough acid to neutralise the alkali. If not I will add more acid, if there is enough acid I will take a reading from the Burette making sure to take it form the bottom of the meniscus.

I will repeat this process until I have recorded all of my results.

I will keep this a fair test by making sure that after every time I do an experiment I wash the flask and the beaker out thoroughly in order to stop any neutralisation before the I start doing an experiment. I will also make sure that I do all the readings in order to stop any change in the way that the results are read.

Prediction

I predict that as the concentration of the alkali decreases it will become neutralised much quicker. Graph 1 shows my prediction.

Reason

The scientific reason for my prediction is this:

As the concentration of the alkali decreases, the number of alkali atoms will decrease. This means that it will take less acid atoms to neutralise the solution. Also as more water is added I order to make the alkali weaker, it will cause the liquid to become more neutral anyway. Therefore requiring even less acid to make it neutral.

Observations

I will include my preliminary experiment. This shows me what range of results I can expect from the real experiment, it also helps me to check if I am doing the experiment correctly.

These are the results I got in the actual experiment:

Analysis

From looking at my results I can tell that my prediction was correct, as the concentration of the solution decreases so does the amount of acid needed to neutralise it.

Graph 2 shows my results, I have drawn on a line of best fit to show the correlation and so that a trend can be easily determined. I can see that it has a strong positive correlation, this tells me that my results are fairly reliable. From the graph I can tell that x is proportional to y, this is because as x goes down, so does y. This information backs up my reason.

The following information explains why my results are as they are.

As the concentration of the alkali decreases so does the amount of atoms, this means that less acid atoms are needed to neutralise the solution.

Evaluation

From my results I can tell that as the concentration of alkali decreases the amount of acid required for neutralisation also decreases.

The experiment went well but could have been greatly improved if I had more time. I could have repeated each concentration more times in order to get better results. From my results I can’t tell if one of them is wrong but if I had three then I could tell an anomalous result from the others. In some of the experiments I may have added a bit too much acid than was needed so if I had more time then I could go slower and make sure I only recorded as much as was required. If I was able to use equipment that constantly keep the solution mixing then I would be able to tell the exact moment it was neutralised.