Energy changes
Read our general notes on Risk Assessment
Does it matter whether you put the acid or base into the calorimeter first and how do you choose what concentrations to use?
Rev writes
It does not matter which goes in first. If you are using expanded polystyrene cups as calorimeters it helps to have two of them. Measure the acid solution into one and record its temperature. Put an equal volume of the alkali into the other and also record its temperature. This allows you to calculate a mean starting temperature before mixing.
The concentration you choose should give you a reasonable temperature change for the total volume of mixture. If 1 mol acid reacts with 1 mol alkali you should use solutions with the same concentration.
If you use 25 cm3 of each solution you will end up with 50 cm3 of final solution. If the solutions are fairly dilute their densities will be the same as that of water. You can estimate the temperature rise given the specific heat capacity of water and knowing that the enthalpy change of neutralisation of a strong acid with a strong base is between 50 and 60 kJ mol-1.
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: 22 November 2003
