Miss Julie

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

Dependent Variable

Amount of Hydrochloric Acid вЂ" 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 вЂ" 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 вЂ" 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 вЂ" 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 вЂ" 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 вЂ" 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.

Apparatus

Pestle and Mortar

Hydrochloric Acid 0.1M HCl

5 different tablet brands of antacid

Beakers 5x 400ml Ð'±0.5

Burette Ð'± 0.05

pH Meter

H2O

Glass Rod

Clamp Stand