For those who dont know it this is the answer (a) NaOH(aq) + HCl(aq) ==> NaCl(aq) + H2O(l) (b) (i) pipette (ii) burette (c) everything with distilled water, then pipette with a little of the NaOH(aq) and the burette with a little of the HCl(aq) (d) pink to colourless, the first drop of excess acid removes the pink alkaline colour of phenolphthalein (e) moles sodium hydroxide neutralised: 0.250 x 25.0/1000 = 0.00625 mol NaOH (remember: moles = molarity x volume in dm3 and its two rearrangements and 1 dm3 = 1000 cm3) (f) moles HCl = moles NaOH (equation) = 0.00625 mol HCl (in 22.5 cm3) (g) concentration hydrochloric acid = 0.00625 x 1000 ÷ 22.5 = 0.278 mol dm-3 (3sf) (scaling up to 1 dm3 = 1000 cm3 to get the molarity) Another way to work it out is 22.5 cm3 = 22.5 ÷ 1000 = 0.0225 dm3 Therefore molarity = 0.00625 ÷ 0.0225 = 0.278 mol dm-3
Posted on: Fri, 04 Jul 2014 11:19:03 +0000
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