Question

to prepare 50 cm³ of 0.1 M NaOH from exactly 50 % (wt/wt) NaOH solution.what volume of the 50 % solution is required​

Answer 1

If the NaOH solution is 50% w/w - then it is necessary to know the density to solve this problem for a volume

50cm³ 0.1M NaOH will contains 50cm³/1000cm³/L * 0.1mol/L = 0.005 mol NaOH

Molar mass NaOH = 40g/mol

Mass of 0.005 mol NaOH = 40g/mol * 0.005 mol = 0.2g

Because the NaOH solution is 50% w/w , weigh out 0.2*2 = 0.4g and deilute to 50mL

Without the density it is impossible to calculate the volume . And in addition, I am sure that you would not be able to accurately measure out the required very small volume of the NaOH solution.