Find out which antacid tablet works most efficiently using a technique called titration.

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Sandip Singh Mangat 10E

Aim:

To find out which antacid tablet works most efficiently using technique called titration.

Measurement:

The measurements will use a titration to find what volume of hydrochloric acid an antacid tablet will neutralise.

Theory:

Our stomachs produce gastric acid to aid in digestion. This acid is mainly composed of hydrochloric acid that is secreted by cells of the stomach lining called parietal cells. Excessive secretion of this acid is common and can lead to many stomach problems such as gastritis, gastric ulcers and peptic acid disease. These disorders are treated by antacids, which reduce the amount of acid in the stomach by various means.

Most antacids contain weak bases and they neutralize the stomach acids by reacting with them chemically. These antacids are best taken for occasional stomach problems and they act very rapidly to provide relief. Some of the most common bases that are used as antacids are:

  • Mg (OH) 2, magnesium hydroxide
  • Al (OH) 3, aluminium hydroxide
  • NaHCO3, sodium bicarbonate
  • CaCO3, calcium carbonate

These chemicals are used because they are weak bases - strong bases would lead to the risk of damaging the stomach if too much was taken. Bases neutralize acids by reacting with them to produce a salt and water. This chemical reaction of a weak base with stomach acid can be written in the general form:

Weak base + hydrochloric acid --> salt + water

A specific example of this chemical reaction is:

Mg (OH) 2 + 2 HCl --> MgCl2 + 2 H2O

There are other forms of antacid that work by less direct means. There are two types of pharmaceutical drugs that act indirectly to reduce the amount of stomach acid. Both of these types drugs act to suppress the formation of stomach acids. Essentially, they turn off the biochemical machinery that produces the stomach acid. These drugs are slower acting than the bases mentioned above, but they provide relief for a much longer time. People with chronic stomach problems usually take them.

Prediction

Tablet = Superdrug

Active Ingredient = 0.5g CaCO3

Relative formula mass (RFM) = 100

Moles of active ingredient = mass / RFM = 0.5 / 100 = 0.005 moles

Equation = CaCO3 + 2HCl >> CaCl2 + CO2 + H2O

Moles of HCl that should be neutralised = 2 x moles of CaCo3 = 2 x 0.005 = 0.01

Concentration of HCl to be used = 1M (1mole per dm3)

Predicted volume of HCl needed = moles/concentration = 0.01/1 = 0.01dm3 = 10cm3

Tablet = Rennie

Active Ingredient = 0.68g CaCO3, & 0.08g MgCO3

Relative formula mass (RFM) = 100, & 84

Moles of CaCO3 = mass/RFM = 0.68/100 = 0.0068 moles

Moles of MgCO3 = mass/RFM = 0.08/84 = 0.0009523809524 moles (13dp)

Equation for CaCO3 = CaCO3 + 2HCl >> CaCl2 + CO2 + H2O

Moles of HCl that should be neutralised = 2 x moles of active ingredient = 2 x

0.0068 = 0.0136 moles

Concentration of HCl to be used = 1M (1mole per dm3)

Predicted volume of HCl needed = moles/concentration = 0.0136/1 =

0.0136 dm3 = 13.6 cm3 

Equation for MgCO3 = MgCO3 + 2HCl >> MgCl2 + CO2 + H2O

Moles of HCl that should be neutralised = 2 x moles of active ingredient = 2 x

0.0009523809524 = 0.001904761905 moles (12dp)

Concentration of HCl to be used = 1M (1mole per dm3)

Predicted volume of HCl needed = moles/concentration = 0.001904761905/1 =

0.001904761905 dm3 = 1.904761905 cm3 

Total predicted volume of HCl needed = 1.904761905 + 13.6 = 15.5047619 cm3 (8dp)

Tablet = Bisodol

Active Ingredient = 0.522g CaCO3, & 0.068g MgCO3, & 0.064g NaHCO3 

Relative formula mass (RFM) = 100, & 84, & 84

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Moles of CaCO3 = mass/RFM = 0.522/100 = 0.00522 moles

Moles of MgCO3 = mass/RFM = 0.068/84 = 0.000809538095… moles (13dp)

Moles of NaHCO3 = mass/RFM = 0.064/84 = 0.0007619047619 moles (12dp)

Equation for CaCO3 = CaCO3  + 2HCl >> CaCl2 + CO2 + H2O

Moles of HCl that should be neutralised = 2 x moles of active ingredient = 2 x           0.00522 = 0.01044 moles

Concentration of HCl to be used = 1M (1mole per dm3)

Predicted volume of HCl needed = moles/concentration =  0.01044/1 =

0.01044dm3 = 10.44cm3

Equation for MgCO3 = MgCO3  + 2HCl >> ...

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