Chemical quantities (AS)
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I have looked at your website for details on how to dilute hydrochloric acid. However I am still confused. I want to dilute the hydrochoric acid and am given that it is 2.00 mol/dm3 and the limewater has a volume of 250 cm3 and concentration of calcium hydroxide of 1 g/dm3. I am using 25 cm3 of limewater. Can you help me on how to dilute the hydrochloric acid ?
Corrie writes ....
To know what concentration of HCl you need you must first work out the approximate concentration of the limewater in mol/dm3 of Ca(OH)2. Let's say this 0.01 mol/dm3 - you will have to do your own calculation.
The ratio in which these two substances react, from the equation, is 2 moles HCl to 1 mole of Ca(OH)2. So if your HCl was the same concentration as the limewater, the titration would need about 50 cm3 HCl for 25 cm3 limewater. This is too much, so it would be better to have the HCl twice as concentrated as the limewater, say 0.02 mol/dm3. This would give similar volumes for the acid and the alkali in the titration.
To make a 0.020 mol/dm3 HCl solution from your 2.00 mol/dm3 solution you would have to dilute it by a factor of 100. To do this you would have to measure out 10 cm3 of 2 mol/dm3 M HCl and dilute it in a graduated (volumetric) flask to 1000 cm3 of solution. Alternatively you could use 5 cm3 diluted to 500 cm3 etc.
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updated: 23 February 2007
