Science / Miss Julie

Miss Julie

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Autor:  anton  09 March 2011
Words: 879   |   Pages: 4
Views: 438

An Investigation to Find Out How much Hydrochloric Acid is Neutralised by Various 100cm3 Antacid Solutions

Dependent Variable

Amount of Hydrochloric Acid – The dependent variable in the investigation is the amount of hydrochloric acid that is neutralised by the antacid solution. The amount of hydrochloric acid that is used will be measured in a burette which makes my results accurate. To make it a fair test the same concentration of hydrochloric acid will be used which will be 0.1M as it is closest to that of stomach acid. The stomach when empties contains 50cm3 of stomach acid, after eating it generally expands so that it holds 1 pint of stomach acid. The more hydrochloric acid that the antacid solution neutralises the more effective the antacid is.

pH of antacid solution – Another dependent variable in this investigation is the pH of the antacid solution. In the method a antacid solution will be made which will have an alkaline pH. As the hydrochloric acid is added this will decrease to become less alkaline, the results for the amount of hydrochloric acid used will be determined by how much is used to change the pH of the antacid solution to a neutral pH 7.0.

Independent Variable

Brand of Antacid Used – In this investigation the independent variable will be the brand of antacid used. Each antacid has a different mass of sodium bicarbonate within the tablet and so will have different neutralising affects on the hydrochloric acid. The equation for the neutralisation of stomach acid is;

HCl + NaHCO3 в†’ NaCl + H2CO3

The carbonic acid which is produced from the neutralisation of the stomach acid is secreted through urine.

Controlled Variable

Temperature – The temperature will be controlled because if the temperature was to be changed this could affect the dependent variable. To control this the experiment shall be done in the same labe with no heatin or no cooling and by using a thermometer so that the temperature can be checked constantly.

Surface Area – The surface area will be maintained throughout the experiment as changing the surface area can affect the dependent variable. To maintain the surface area throughout the investigation, the antacid solutions will be kept in the same size flasks and therefore will have the same size base.

Concentration – The concentration of hydrochloric acid will be kept the same throughout the investigation. To make it more alike to stomach acid the hydrochloric acid should be 0.1M.

Other ways in which the investigation will be controlled is by using the same equipment for all the experiments. I will be using the same measuring equipment to measure the water and take the measurements for the hydrochloric acid.


Pestle and Mortar

Hydrochloric Acid 0.1M HCl

5 different tablet brands of antacid

Beakers 5x 400ml В±0.5

Burette В± 0.05

pH Meter


Glass Rod

Clamp Stand


1. Using the pestle and mortar crush 2 tablets of the antacid until it is a fine powder.

2. Fill the mortar with water, and using the glass rod transfer to a beaker.

3. Make sure that none of the powder is lost, and once transferred to the beaker wash out again with water to ensure that any remaining contents are washed out.

4. Mix the contents of the beaker until all the antacid is dissolved into the water.

5. Fill the beaker until it contains 100ml of the antacid solution, then measure the pH by placing the pH meter probe into the solution.

6. Before using the burette wash it out with hydrochloric acid.

7. Once washed out refill the burette with hydrochloric acid ensuring that the tap is closed.

8. Place the beaker containing the antacid solution underneath the burette, ensuring that the pH probe is still in the solution and a clear reading can be seen.

9. When ready open the tap, so that the burette produces drops of hydrochloric acid ensuring that the tap is not opened far enough that a steady stream of hydrochloric acid is released.

10. When the pH of the antacid solution has reached 7.0 close the tap on the burette and take a measurement of how much hydrochloric acid has been used. The antacid which uses the most hydrochloric acid is the most effect.

11. Repeat steps 1-10 for each brand of antacid and making sure that 3 repeats is done for each antacid.


When handling the hydrochloric acid make sure that care is taken. Avoid contact with the eyes or skin as it can cause serious permanent damage. If contact is made with the eye, immediately flush the eye with water for ten minutes then seek medical help, while if contact is made with the skin, wash area with plenty of water and remove any contaminated clothing. If swallowed drink plenty of water and seek medical help. Always wear safety glasses when handling hydrochloric acid.


The results for the investigation can be shown in many forms. They can be tabulated and also shown in the form of a bar chart to show how much hydrochloric acid was used by each antacid solution. An example of a table that can be used for results can be seen on the following page.

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