Deducing the quantity of acid in a solution

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Chemistry coursework:        Sofia Gaggiotti

Deducing the quantity of acid in a solution

Sofia Gaggiotti

Chemistry coursework:

Deducing the quantity of acid in a solution



Aim and Background information        3

Hazards        3

Protection        4

Method        5

Previous calculations        5

Making the Solution        6

Equipment needed        6

Quantities of materials needed        8

Procedure        8

Making the Titration        9

Equipment needed        10

Procedure        13

References        15

Results and calculations        16

Evaluation        19

Chemistry coursework: Deducing the quantity of acid in a solution

Aim and background information

The aim of this experiment is to find how to develop and determine an accurate, precise and reliable concentration of an acid rain solution.

To do this, we are going to make first a solution of sodium carbonate with distilled water and then a titration in order to calculate the concentration of sulphuric acid in a solution.

Solution: a solution is a   composed of two or more substances. In this mixture, a solute is dissolved in a solvent.

Solutions are characterized by interactions between the solvent phase and solute molecules or ions that result in a net decrease in free energy.

Titration: a titration is a laboratory technique by which we can determine the concentration of an unknown reagent using another reagent that chemically reacts with the unknown. At the equivalence point (or endpoint) the unknown reagent has been reacted with the known reagent. A chemical indicator (for example, a change in the colour of the unknown) will let us know when that point has arrived.

This symbol equation explains the reaction that we are doing. This shows that the moles of sodium carbonate used are the same number of moles used of acid sulphuric.

Na2CO3 (aq) + H2SO4 (l)     →   Na2SO4 (aq) + H2O (l) + CO2 (g) 


In this experiment, the substances used and their hazards are:

  • Sulphuric acid

Given the concentrations of H2SO4 used (between 0.05-0.15), it can not be labelled as irritant because irritant solutions should be equal to or stronger than 0.5 M and weaker than 1.5 M. Therefore, this concentration of acid has not got any risk.

However, we will still be taking precautions in order to avoid any possible harm.

We will use goggles to avoid acid contact with the eyes and gloves to avoid direct contact with the hands when using it.

Also, if the acid is spilt on skin or clothes we will rinse it with water and then wipe it using a dry cloth.

If it spills either on the floor or on the table, we will clean it up using a damp cloth with water.

  • Methyl orange

Methyl orange is toxic if swallowed or inhaled. In solutions, like the one we are preparing, the hazard is very low (because they are less than 1% by mass). Also, methyl orange can be highly flammable.

In order to be precautious and preventive, we are going to use eye protection (goggles) and ensure there are no flames near as it is flammable.

If the methyl orange spills accidentally on skin, we will wash it properly with soap and water. Again, if it spills on the floor or table we will remove the contaminated section using a wet cloth.

  • Sodium Carbonate

We used solution of sodium carbonate both as a solution and as powder. Its concentration is 0.1 M, so it can not be labelled as irritant because only solutions equal to or stronger than 1.8 M are irritant. However, eye protection will still be used in order to avoid any eye contact given the sensitivity of the eyes.

If the solution spills, we will rinse the contacted area with water. If it spills on our eyes, we will flush them with plenty of water. If it hurts, then we will contact a doctor.

Solid sodium carbonate may be slightly toxic if ingested. However, given the amount used, 2.65g, that’s very unlikely to happen.


Despite the hazards being reduced because of the small quantities used, precautions will still be taken in order to avoid any potential harm.

To prevent any harmful contact with sulphuric acid, methyl orange and sodium carbonate, we are going to use gloves and safety glasses.

Also, we will ensure there is always suitable ventilation in the room and no flames around.

Also, given that we are using glass ware, we need to know what to do if it is broken. The most important part is to be very careful because it can cut and cause harmful wounds.

First of all, if any glass equipment fall, we need to tell the teacher and ensure everybody is aware of the danger. Then, we need to sweep it thoroughly to ensure no shards remain and put it into the glass bin.


First of all, we have to make a solution of anhydrous sodium carbonate with water in order to get a liquid solution and then be able to identify the concentration of acid by titration.

Calculations before starting the solution:

We know that the concentration of the acid solution (Na2CO3) must be between 0.05 and 0.15. From these numbers, and in order to work as accurate as possible, we will assume that we can titrate is with 0.10 M concentration of sodium carbonate.

Also, we know that we want finally to obtain 250 cm3 of the solution. 250cm3 will allow us to have enough solution to make several titrations, and therefore obtain more reliable results.  

Knowing the concentration and the volume, we can calculate the number of moles of Na2CO3 and then the mass needed to prepare the solution.

First of all we need to change from cm3 to dm3, in order to have the wanted units.  

250 cm3 = 0.25 dm3

Knowing that n (number of moles) = C (concentration) x V (volume)

n = 0.1 mol/dm3 x 0.25dm3

n = 0.025 moles of Na2CO3

Mr of Na2CO3 = 3x2 + 12 + 16x3

Mr of Na2CO3 = 106

As m (mass) = n (number of moles) x Mr

m = 0.025 x 106

m = 2.65g of Na2CO3

Now that we have the amount of the Na2CO3 (2.65g) needed and the volume of distilled water that we are going to use (approximately 250cm3), we have to make a solution of anhydrous Na2CO3 with distilled water in order to get a liquid solution and then be able to get the wanted concentration by titration.

Making the solution:

Equipment needed:

  • Electronic balance: an electronic balance measures to 2 decimal places; this will give us an accurate weight of the solid used.

  • Weighing boat

A weighing boat is a container used to prevent reagents from contacting the balance pan. They are made of polypropylene, a plastic that does not absorb water. This allows us to rinse it once the solid is weighted and this will ensure that the entire solid has been used, so more reliable results will then come out because we will not waste any sodium carbonate. They are also inexpensive and do not need to be handled with care.

  • Beaker

A 250 cm3 beaker will allow us to mix the solution properly. It is big enough to mix the solution properly and avoid any solution spilt, what will make our results more reliable. Also, it can hold solutions of  chemicals, as they are made of  (a material used to coat cooking utensils and in industrial applications where sticking is to be avoided) or other materials resistant to corrosion.

  • Mixing rod: A mixing rod is used to mix the solution and to ensure that the entire solid (in this case, Na2CO3) has been dissolved.

  • Funnel

A funnel is needed to add the solution into a volumetric flask. Using a funnel is a careful way of adding a solution into a flask. The solution could accidentally spill if adding it directly from the beaker.

  • Volumetric flask

A volumetric flask has a precise graduation line in the neck of the flask. A part of the solution is placed into the flask, and then more solvent is added to bring the total volume up to the graduation. We are going to use a 250cm3 one in order to ensure we have enough solution for the whole titration.

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  • Pasteur pipette

A Pasteur pipette is small enough to allow us to add very small quantities of solvent. We use it to add the last centimetre before reaching the graduation mark of the volumetric flask. Also, they are very light and it is possible to be watching the meniscus whilst adding solvent.

Quantities of materials needed:

  • 2.65g of Na2CO3
  • Approximately 250cm3 of distilled water



Using an electronic balance, which is quite accurate because it can measure to 2 decimal places, we will ...

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Grammar, spelling and punctuation all to a very high standard.

Use of chemistry equations correct. Clearly defines any hazards in the experiment to a high level and quotes from a range of different sources showing clear research behind the experiment. Calculations included to determine reagents also seem fine. High standard of coursework to be calculating measurements from scratch rather than using set measurements. Very detailed and accurate method, and details of each part of the equipment used and what they are used for, not sure the candidate needs to go into what each piece of equipment is used for, but to this level even a new chemistry a level student would start to understand the procedure taking place in front of them. Their evaluation and results calculations are very detailed, correct and to a very high level of understanding. Calculated most possible errors that could have affected the experiment and suggests possible improvements, although there could have been slight more detail about the improvements suggested.

Exceptional piece of coursework. Aims and background information are very clearly worded, and explains the chemistry theory behind the practical well. I would like to see the use of the experiment in the real world more clearly defined. Main body of text, conclusions and evaluation all to a very high level and standard and this candidate is exemplary for the level I would expect for an A level student.