Practical investigations
Read our general notes on Risk Assessment
I am planning a titration in order to determine the number of moles of water of crystallisation in sodium carbonate using HCl. I need to acknowledge any possible chances of inaccuracy in the equipment or method process (since I know that a burette has a low error margin), and any safety measures that need to be taken besides the usual lab procedures. Please help!
Igloo writes
You need to list all the pieces of apparatus you used and in each case estimate the accuracy to which readings can be made. In your case this would probably be:
Balance: e.g. accurate to 0.1g
Volumetric flask: ------
Pipette: -------
Burette: --------
I’ll leave you to mention any other apparatus in which measuring was carried out and to fill in accuracies (I’ve given you an example with the balance)
You then need to convert these accuracies into percentage errors using your readings. For example, if the balance is accurate to 0.1g and you measured out 1.4 grams of solid, the actual mass could have been as low as 1.35g or as high as 1.45g and the percentage error is (0.05/1.4) x 100 = 3.6% = about 4%. If you repeat this for all the other apparatus and add together the percentage errors you will finish up with a total error to quote in your report. If you wish to know more about writing your report and calculating errors in this way I have provided two web references for you to look at, where everything is explained in more detail.
Planning your investigation
http://www.rod.beavon.clara.net/err_exp.htm
As for safety measures you should ask your lab technician to let you have access to the relevant Hazcards, or safety leaflets, and find out the appropriate safety data for the chemicals you used, i.e. solid sodium carbonate, hydrochloric acid (you will need to know its concentration and read off the data relevant to this concentration). Also you need to think of the products of this reaction. Is a flammable gas given off, such as hydrogen? Of course not, but do consider the products as well as the reactants in order to give a comprehensive account of the safety measures.
We are not qualified to give safety advice on React. 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: 11 May 2006
