Neutralise Excess Stomach Acid

Controlled Variables: Mass of Indigestion Remedy: This must be kept the same throughout the experiment, for each powder. I checking that the mass of the powder is accurate to the exact 100th of a gram will ensure this. This is important because if any more or any less of the remedy is used, it will change the amount of HCl needed to neutralise it. Volume of Water: I will use 25.00ml of water throughout the entire experiment. Like above, if the amount of water is changed in the middle of the experiment, it will change the amount of HCl needed to neutralise the solution. Concentration of HCl This is important, because I need to have the concentration as close to that of real stomach acid as possible. 0.5 mol is available to me. This is close enough. If the concentration was any higher, it would take a smaller amount to neutralise the solution, and if there was a lower concentration, then it would take more. Room Temperature This is important because if the room temperature was much higher or lower in one session than in another, the experiment would have been greatly affected. This is because a higher temperature would increase the energy that the particles of any of the chemicals would have more energy than on another day. This is one reason why I tried to do all the experiment during one one hour session.

Uncontrolled Variable: I have chosen to only measure for one uncontrolled variable. The main reason for this is to have time, and it is far simpler. This variable is: Volume of HCl added to the solution I used this as the uncontrolled variable instead of the amount of solution added to the HCl because it is a lot easier to control and measure. Had I done the other way round, then I would have constantly needed to clean a lot of my equipment before and after each test. It is also easier to calculate the results this way round.

Method: The apparatus was set up as shown in the diagram below. I accurately measured out 2.00g of stomach remedy powder in clean 100ml beakers using the top-pan balance. The beakers needed to be as clean as possible to avoid contamination of the solution. I did this for all four of the given remedies, twice for each so that I could identify anomalous results if there were any. Then I added 25.0ml of water to each. I did this using a measuring cylind ...