Question

How would you prepare 500 ml of a .50m solution of naoh from a 2 m stock solution

Answer 1

Explanation:

i.e M = m/V(L)

M= Molarity of substance

m = number of moles of substance (i.e solute)

V(L) = volume of solution in Litres

So talking about our question molarity should be 0.5 M,volume should be 0.1 L , and we should know that Molar Mass of NaOH is 40 because Atomic mass of Sodium i.e (Na known as Natrium) is 23,Atomic mass of Oxygen (O) is 16 and Atomic mass of Hydrogen is 1.

Adding them all up gives Molecular mass of NaOH as 40

So if we solve above equation we get no of moles of NaOH present in 0.1 litres of solution

Let’s do that math

Rearranging equation we get m=M×V(L) i.e m= 0.5×0.1 =0.05. So 0.05 moles of NaOH are present in 100 ml of 0.5 Molar solution

Now we also know that to find no of moles of a substance we have a formula and it is m=W/Mw where

m = no of moles of a substance

W = Mass of substance

Mw = Molecular weight of the substance

So substituting all values and rearranging equation we get mass of NaOH as

W=m×Mw = 0.05×40=2 grams

Hence we found the required mass of NaOH as 2 grams.

Now talking about shortcut

we know as explained above M=m/V(L) and m=W/M

Substituting value of m(no of moles) in M=m/V(L) we get M=WMw×V(L)

Try substituting the values yourself and get the answer

Note :: The value of Volume should always be substituted in terms of Litre only. That is the reason i used the letter (L) at all the places with V

So thats all get the answer and comment any other problems below

Hope you got your problem solved

Thanks!!!