Write a SOP (standard operating

procedure) for doing a titrationDo not use your books

Hints – diagram, use known/unknown/ tips

Assessment at AS

Unit F331Chemistry for Life

Unit F332Chemistry of Natural Resources

Unit F333Chemistry in Practice (internal assessment)

Elements of LifeDeveloping Fuels

Elements from the SeaThe AtmospherePolymer Revolution

Five practical skills

15% of A level 25% of A level 10% of A level

Written paper1 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

CI p371

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. 13.5 cm3 of the acid was required for neutralization. Calculate the concentration of the potassium hydroxide solution.

Step 1Write down everything you know from the question. I put

the one we know most about on the left Hydrochloric Acid Potassium hydroxideVolume used = 13.5 cm3 Volume used = 10.0 cm3Concentration = 0.10M Concentration = TBD

Step 2Write 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 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 = concentration

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 × concentration

Never do cm3!

Step 4Work 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 = 0.0014 mol Number of moles KOH = 0.0014 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) – 0.0014Volume (q) 10cm3

Concentration = 0.14 MNumber of Moles = volume × concentration

CH3COOH + NaOH H2O + NaOOCCH3

• 0.1M NaOH ? CH3COOH• Volume 6cm3 10cm3 • Balance equation• No. moles = Vol dm3 x conc.• ? = (6/1000) x 0.1Moles dm-3

• ? = 6 x 104 Moles• 1:1 ratio thus 6 x 104 Moles of acid• So Conc = Moles/vol dm3 = 6 x 10 4 / (10/1000)• = 0.06 Moles dm-3

Deduce the concentration of hydrochloric acid if 20.0cm3 is neutralised by 25.0cm3 of sodium hydroxide at 0.2oo moldm-3?

Carry out a titration?Confident with procedure?

Confident with calculations?

What to do if you’re 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 15.1-6 qs

+ ready to speak