Question

Make a buffer with this solution: 0.1M NaCl, 0.5M Tris, 0.02% NaN3, pH 7.5, 500ml buffer

please provide detailed steps and explanations, thx

Answer 1

1.Weigh 30.285 gm of Tris.

Calculation: molarity of Tris .5,total volume 500 ml or .5 litre i.e .5*.5 =.25 moles of Tris needed. Molar mass of Tris 121.14g/mol.so .25*121.4=30.285 gm Tris should be weighed.

2.Weigh 2.922 gm of Nacl.

Calculation: molarity of NaCl .1,total volume .5 litre so .1*.5=.05 moles of Nacl needed.Molar mass of Nacl 58.44g/mol so .05*58.44 =29.22 gm of NaCl needed.

3.take .1 ml of NaN₃ solution.

Calculation: .02 %=.0002, so .0002*500=.1 ml of NaN₃ is needed.

4.Dissolve the required mass of Tris and NaCl and required volume of NaN₃ in approximately 160 ml of deionised water.(1/3 rd of total volume).

5.Using a pH meter titrate titrrate the solution with HCl until the correct pH reached.

6.Add this mixture to a volumetric flask of 500 ml and fill up the remaining volume with deionised water.