Question

The volume of water added to 500ml,0.5M NaOH solution so that its strength becomes 10mg NaOH per ml?

Answer 1

about 500mL

Explanation:

A concentratio of 10 mg/mL is equal to 10g/L and since NaOH has a MM of 40 g/mol it also equal to `M= (10 g/L)/((40g)/(mol))= 0,25 (mol)/L` .
since n° of mol in a solution is equal to `M xx V` you can write both for diluite solution and for the concentrate solution :`M_c xx V_c = M_d xx V_d`
that is
`5 (mol)/L xx 0,500 L = 0,25 (mol)/L xx V_d`
`V_d = 1,000 L` and you must add about 500 mL.
In truth the volume of different solutions aren't addiditive so is more convenient that you take an one liter flask and you add water up to the notch