Practical investigations
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I am currently doing an AS planning exercise to find the % purity of magnesium carbonate(MgCO3) in an indigestion tablet using a titration. Is it advisable to use sulphuric rather than hydrochloric acid, due to the fact that there would almost certainly be chalk (CaCO3) in the tablet? Please help!
Ulex says
The thinking is that if calcium carbonate reacts with sulphuric acid, the resulting calcium sulphate, being sparingly soluble, protects the rest of the calcium carbonate from attack. As calcium chloride is freely soluble, the use of hydrochloric acid will treat calcium and magnesium carbonates equally. Since, however, the carbonates are likely to be powdered, I am not at all sure that this argument holds good. In answer to a similar question recently, I advised using both acids, in separate experiments, to see if there is a difference in the outcome. On balance, I offer the same advice now.
Always carry out a risk assessment and check with your teacher before starting any practical work.
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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updated: 19 January 2006
