Presentation on theme: "Write a SOP (standard operating procedure) for doing a titration Do not use your books Hints – diagram, use known/unknown/ tips."— Presentation transcript:
Write a SOP (standard operating procedure) for doing a titration Do not use your books Hints – diagram, use known/unknown/ tips
Assessment at AS Unit F331 Chemistry for Life Unit F332 Chemistry of Natural Resources Unit F333 Chemistry in Practice (internal assessment) Elements of Life Developing Fuels Elements from the Sea The Atmosphere Polymer Revolution Five practical skills 15% of A level25% of A level10% of A level Written paper 1 hr 15 min Written paper (one question on an Advance Notice passage) 1 hr 45 min Internal assessment of skills using materials and mark schemes provided by OCR
Content Process Benefit Skill of carrying out a titration Calculate unknowns and percentage uncertainty Carry out a titration Help in 10% of AS grade!
ES4.1 Carry out titration Put your results on the board Use the booklet to help write your results
The question: 10.0 cm3 of a solution of potassium hydroxide was titrated with a 0.10 M solution of hydrochloric acid cm3 of the acid was required for neutralization. Calculate the concentration of the potassium hydroxide solution. Step 1 Write down everything you know from the question. I put the one we know most about on the left Hydrochloric Acid Potassium hydroxide Volume used = 13.5 cm3 Volume used = 10.0 cm3 Concentration = 0.10M Concentration = TBD
Step 2 Write the BALANCED 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 dont have to worry about any ratios. Step 3 Calculate 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 = concentration
Step 3 Calculate 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 × concentration Never do cm 3 !
Step 4 Work 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. Number of moles of HCl = mol Number of moles KOH = mol – they react in a one to one ratio
Step 5 Work out the concentration of the potassium hydroxide. Moles of KOH (same as HCl as 1:1) – Volume (q) 10cm 3 Concentration = 0.14 M Number of Moles = volume × concentration
CH 3 COOH + NaOH H 2 O + NaOOCCH 3 0.1M NaOH ? CH3COOH Volume 6cm 3 10cm 3 Balance equation No. moles = Vol dm 3 x conc. ? = (6/1000) x 0.1Moles dm -3 ? = 6 x 10 4 Moles 1:1 ratio thus 6 x 10 4 Moles of acid So Conc = Moles/vol dm 3 = 6 x 10 4 / (10/1000) = 0.06 Moles dm -3
Deduce the concentration of hydrochloric acid if 20.0cm 3 is neutralised by 25.0cm 3 of sodium hydroxide at 0.2oo moldm -3 ?
Carry out a titration? Confident with procedure? Confident with calculations? What to do if youre not?
Best Choice – Salters A level / ES Formula, equations, amount / Titrations and titration calculations Next lesson is halogen production conference – have poster with you and all qs + ready to speak