Investigating antacids.

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Investigating antacids 

Aim: To discover the most effective and useful base for use as an antacid using both chemical and medical evidence to make a final judgement.

The formulae for the neutralisation of each base are as follows: 

Mg(OH)2 + 2HCl → MgCl2 + 2H2O

Mr: 92     + 80      =  172

       0.2g  + 1.8g = 2g

     0.0022  + 0.0225        

CaCO3 + 2HCl → CaCl2 + CO2 + H2O

Mr: 100 + 80    =   180

       0.2g + 1.8g = 2g

       0.0020 + 0.0225        

MgCO3 + 2HCl → Mg(Cl)2 + CO2 + H2O

Mr: 84   + 80     =   164

       0.2g + 1.8g = 2g

       0.0023 + 0.0225

MgO + 2HCl → MgCl2 + H2O

Mr: 40 + 80    =  120

       0.2g + 1.8g = 2g

      0.005 + 0.0225

NaHCO3 + HCl → NaCl + CO2 + H2O

Mr: 84   +    37        =  71

      0.2g + 0.9g = 1.1g

      0.0023 + 0.0243

We are using 0.5M Hydrochloric acid for the titration and we would therefore expect that 0.9g of HCl is being neutralised throughout. (0.05ℓ x 18g = 0.9g HCl)

You would expect that the magnesium based compounds would be the most efficient antacids because they have high formula masses that are greater than or close to the amount of HCl being neutralised, in particular MgO which has a formula mass of 0.005 and is neutralising HCl of 0.0225.                                                            

Apparatus: 50ml burette and stand, burette funnel, glass beaker, pipette, conical flasks, Hydrochloric acid (0.5M), selection of bases (Magnesium hydroxide, Calcium carbonate, Sodium bicarbonate, Magnesium oxide and Magnesium carbonate), balance, glass rod, glass pipette, methyl orange, pestle and mortar, distilled water, white tile

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Method: Tip a small amount of a base into the pestle and mortar, grinding it to remove any larger lumps. Now place the base onto the balance and add, remove a small amount of the substance as necessary until it weighs 0.2g. Place this into the conical flask. Place the white tile onto the base of the burette stand. Using the glass pipette, measure 25ml of water and add it to the conical flask containing the base and ensure that as much as possible is dissolved. Now add 5 drops of methyl orange to the solution. Place the burette funnel ...

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