You can use the formula V1C1 = V2C2.

e.g- 5% ammonia solution,you need 100 mL of 5% ammonia,from 25% ammonia solution

V1 x 25 = 100 x 5. Solving the equation, V1 = 20. Therefore you need to add 20 mL of 25% ammonia to 80 mL of water to get 100 mL of 5% ammonia.

Other procedure

Lets assume 1 liter of the 5% solution.

From 25 to 5 % means you need to dilute 5 times.

So 1/5 of 1 liter will be from the 25% solution.

So take a volumetric flask of 1 liter, add 200 ml ( = 1/5th) of the 25 % solution, then add distilled water till the one liter mark, put a stopper one and shake it, done.

Dear Su jia Nan

First you prepared 1000 ml of 1 M KOH analyte solution.

Most of bottle of ammonia solution they mention the concentration or percentage or like 1 ml = 1 mg of NH3.

You know the Molar mass of ammonia is 17.031 g/mol ( 17.031 g NH3 in 1000 ml 1M KOH = 1 M NH3 in 1 M KOH solution)

So, you can prepared desired amount of .1 M NH3 by adding required amount of NH3 solution in KOH analyte.

Best Regards,

Bapi