Step 1 - A statement that there should be an excess of acid, Step 2 - Moles of acid = 50 0 x 0.200/1000 = 1.00 x 10-2 mol 2 mol of acid react with 1 mol of barium hydroxide, Step 3 - therefore moles of solid weighed out should be less than half the moles of acid = 0.5 x 1.00 x 10-2 = 5.00 x 10-3 mol, Step 4 - Mass of solid should be < 5.00 x 10-3 x 171.34 = <0.857 g, Step 5 - Measure out 50 cm3 of acid using a pipette and add the weighed amount of solid in a conical flask, Step 6 - Titrate against known concentration KOH - 0.100 (or 0.200) mol dm-3, Step 7 - KOH added from a burette and record the volume (v) when an added indicator changes colour, Step 8 - Calculate Mr from the experimental data as below,, Step 9 - Moles of hydroxide = 5.00 10-3 - (v x conc KOH)/1000 = z mol, Step 10 - Mr = mass of solid / z,

AS Chemistry Model Assignment Alternate to Practical Question Order of Steps Involved

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