Practical investigations
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For my investigation I need to find how the percentage mass of magnesium carbonate in an indigestion tablet can be determined by
1. thermal decomposion
2. reacting with an acid
I am lost as Ii cannot find much information about this on the web.
You do not need a web site to work this out - you need to remind yourself of how to calculate theoretical yields (mass or volume) from balanced equations.
For example, the balanced equation for the thermal decomposition of magnesium carbonate allows you to work out the volume of gas expected (under stated conditions) from a measureed amount (in moles) of the carbonate. If you do the experiment accurately, but less than the expected volume of gas (because the carbonate was impure) then you can work our the percentage purity.
A similar approach can be applied to the reaction of the magnesium carbonate with hydrochloric acid. Here is is best to added a measured excess of a standard solution of the acid to a measured amount of the carbonate. Then use a titration with standard alkali to find the amount of excess acid.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
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I was massively stuck with this problem too. I found your response gave me a place to start so I just wanted to say thank you.
Steph Crann 09 April 2005
updated: 04 April 2005
