Need help on AS chemistry (AQA)

[NRSRBO]

Hello, I've got this past paper and I'm stuck on the questions. Any help given for any of the questions would be very much appreciated.

Further information required:
Average titre: 26.20cm^3
Vol. of solution Y: 25cm^3

(See attached .zip file)

 

[aalmuhannadi]

2. n = cv = (26.2/1000) * 0.1 = 0.0026 mol
3. From the equation, 2 mol HCl is required for each mol of sodium carbonate, therefore 0.0026 / 2 = 0.0013 mol of Na2CO3 is used.
4. c = n/v = 0.0013 / (25/1000) = 0.052 mol dm^-3

 

[NRSRBO]

Thank you very much for you help.

If you or anyone else could help further I'd appreciate it very much.

Thanks again