The concentration of a solution is shown in Moles. The equation for working out the molarity of a solution from the volume of acid and base used is
Na = Ma x Va
Nb Mb x Vb
In this equation, Na stands for the number of moles in the acid, Nb stands for the number of moles in the base. These figures are obtained from the balanced equation. Ma stands for the molarity of the acid, and Mb represents the molarity of the acid. Va and Vb represent the volume of the acid and base respectively.
The number if moles in the acid and base can be worked out from the balanced equation and the molarity can then be worked out once the volumes have been put in.
Pilot experiment
Diagram:
Method:
1)A burette was clamped and then filled to the top with Sodium Hydroxide (NaOH) using a funnel. A small amount was run through the tap to ensure there were no air bubbles.
2)The reading was taken from the burette at eye level, from the bottom of the meniscus and recorded.
3)A conical flask was taken and using a valve pipette filler, 10cm³ of Vinegar A (Ethanoic Acid CH3COOH) was put into it. It was ensured that the amount was accurate by touching the pipette to the side of the flask.
4)Three drops of Phenol Phthalein were added to the Ethanoic Acid in the flask. This is colourless in acids and pink in alkalis.
5)The Conical Flask was placed beneath the burette and on a white tile to enable any colour change to be seen easily.
6)The alkali was added to the acid slowly, by cradling the burette tap with the left hand and using the right to swirl the conical flask.
7)All colour change was observed, when a strike of pink was seen, that wouldn’t disappear, the alkali was added slower.
8)When sufficient alkali had been added to the acid, the reading was taken and recorded.
9)A final titre was recorded.
10)This was repeated with solutions B, C, D and E.
Results:
Analysis:
We can tell from this pilot that some of the solutions has been diluted. Solution A shows the amount of alkali that should be used to neutralise vinegar that has not been diluted. However, we can see that for some of the other vinegar, the amount of alkali is less, which shows that it has been diluted. Having obtained the rough titre from this experiment we can be more accurate in the real experiment.
In the real experiment, I will increase my range by testing Solutions C and E as well. I will also repeat the tests to ensure a valid result.
Prediction
I predict that if any of the solutions have been diluted, the amount of alkali needed to neutralise them will be less. If they have not been diluted the amount of alkali used will be the same as for solution A.
Key Variables:
For a fair test only one variable must change, and that is the thing that you are investigating. In this experiment I am investigating the volume of alkali needed to neutralise different acids. This is the dependent variable.
The independent variable is concentration of the vinegar, or Ethanoic acid. I have 5 different acids to test.
I will keep the alkali I use the same by always using Sodium Hydroxide, NaOH. I will keep the concentration of NaOH the same by ensuring I use a 1M solution each time. I will always keep the acid the same by always using Ethanoic acid, CH3COOH. Although the concentration will vary, the amount will always stay the same.I will also ensure that I use the same apparatus each time.
Real Experiment
Diagram:
As for pilot.
Method:
1)A burette was washed out twice using distilled water, clamped and then filled to the top with Sodium Hydroxide (NaOH) using a funnel. A small amount was run through the tap to ensure there were no air bubbles.
2)The reading was taken from the burette at eye level, from the bottom of the meniscus and recorded.
3)A conical flask was taken and washed out with distilled water, using a valve pipette filler which had also been cleaned, 10cm³ of Vinegar A (Ethanoic Acid CH3COOH) was put into it. It was ensured that the amount was accurate by touching the pipette to the side of the flask.
4)Three drops of Phenol Phthalein were added to the Ethanoic Acid in the flask. This is colourless in acids and pink in alkalis.
5)The Conical Flask was placed beneath the burette and on a white tile to enable any colour change to be seen easily.
6)The alkali was added to the acid slowly, by cradling the burette tap with the left hand and using the right to swirl the conical flask.
7)All colour change was observed, when a strike of pink was seen, that wouldn’t disappear, the alkali was added slower.
8)When sufficient alkali had been added to the acid, the reading was taken and recorded.
9)A final titre was recorded.
10)This was repeated with solutions B, C, D and E ensuring that the apparatus was washed out thoroughly each time.
Results:
I only got one anomolous result. This is a result which is very different to the others, which means that an error has been made in that test. Anomolous results should be ringed, and I have not included it in my average.
Calculations: