Titration Calculations: Relative Molecular Masses and Number of Moles

Titration CalculationsBefore you go any further, check that you can do the following… Calculate: Relative molecular masses from a given chemical formula Calculate: Number of Moles from the mass/RMM equation Manipulate: The number of moles equation to get the form you require. When you are confronted by a Titration calculation the first rule is: DON’T PANIC! The Second rule is read through the question very carefully.The Third rule is read through the question carefully again! We are now going to look at a question and hopefully guide the unbelievers (henceforth known as infidels) through a titration calculation. If you know how to do these, go straight to the questions at the end.The question:10.0 cm3 of a solution of potassium hydroxide was titrated with a 0.10 M[1] solution of hydrochloric acid. 13.5 cm3 of the acid was required for neutralization. Calculate the concentration of the potassium hydroxide solution.Step 1Write down everything you know. Placing the one you know most about on the left (you don’t have to do this, but its just a good idea). Hydrochloric Acid Potassium hydroxideVolume used = 13.5 cm3 Volume used = 10.0 cm3Concentration = 0.10 M Concentration = TBD[2]Step 2Write the equation or as much as you know about it. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) This is necessary to check out the ratios of reactants – in this case 1:1 so we don’t have to worry about any ratios.Step 3Calculate the Number of Moles used of the reactant you know most about. In this case the HCl(aq) The rule here is Number of Moles = volume × concentrationStep 3Work out how many moles of the unknown you have used, this is where you may need to multiply up or down the number of moles, so if 1 mole of HCl needed 2 mol of potassium hydroxide, then at this point you would multiply the number of moles of HCl by 2. In this case this is unnecessary.