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HELP please??

Can anyone tell me if I have answered these questions correct please? I am doing Fast Track A Level Chemistry which means I get lots of homework but not much much feedback on my answers!

Titration Problem.
1.84g of an acid HA was dissolved in 250cm3 of solution in a volumetric flask. 25.00cm3 of this solution was pipetted into a conical flask and 4 drops of indicator added to it.

25.00cm3 of solution of HA required 24.55cm3 of the NaOH solution for neutralisation to occur. The NaOH solution has a concentration of 5.00g.dm-3

Questions.

a). Calculate the concentration (in mol dm-3) of NaOH

mol NaOH = Mass/Mr = 0.02455/40 = 6.14x10-4 mol

C=n/V = 6.14x10-4/0.02455 = 0.0250 mol dm-3

b). Calculate how many moles of NaOH were used in the titration.

n= n x V = 0.0250 x 0.02455 = 6.14 x10-4 mol

c) Determine the number of moles of HA which reacted with NaOH in your titration ( HA (aq) + NaOH (aq) = NaA (aq) + H2O (l) )

Mole ratio HA : NaOH
1: 1
6.14x10-4 mol : 6.14x10-4 mol

d) Calculate how many moles of HA were dissolved in the 250cm3 of solution in the volumetric flask

In 25cm3 there are 6.14x10-4 mol of HA
So in 250cm3 6.14x10-4 x10 = 6.14x10-3 mol

There is another question which is:

e) Use the mass of HA which was weighed out and your answer to (d) to calculate the relative molecular mass of acid HA.

I have not attempted the last question yet because I am not sure if my previous answers are correct.

If anyone can give me any help at all I would be very grateful because I am very confused right now!! Thank you :smile:

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