Group 2: Alkaline earth metals
Read our general notes on Risk Assessment
How do I identify a Group 2 hydroxide (from Ca, Sr, or Ba), by determining its relative formula mass using titration?
Ulex replies
The key to this is that you know the formula will be of the type: M(OH)2 where M is the symbol for the Group II metal.
So what you do is to weigh out a suitable sample accurately and dissolve it in water. Make sure it all dissolves!
Make up this solution with water to a known volume using a volumetric flask. Titrate pipetted volumes of this solution with hydrochloric acid of known concentration, using a suitable indicator. You may have to experiment with the concentration of the acid to obtain a reasonable burette reading.
Then work out from your result what mass of the hydroxide reacts with 2 moles of HCl. This mass will be the molar mass, which is numerically the same as the formula mass. If you know the formula mass and the formula of the hydroxide, you can now work out which metal it contains.
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: 14 August 2007
