Question

Find the amount of Na2CO3 in grams to make solution of 250 ml with N/10 normality.

Answer 1

Okay, so here is how you do it 
First, you find the moles of sodium carbonate in the given solution.
moles=concentraton x volume (n=cv)
=0.1mol/dm3 x (250/1000)dm3
(0.1M = 0.1mol/dm3 and converting 250ml into dm3 by dividing by 1000)
=0.025mol
Next, you find out the molecular mass of Na2CO3=
( 23 x 2) + 12 + (16 x 3)
= 46 + 12 + 48
=106 (g/mol)

Then, you find out the mass of Na2CO3 needed to give .025 mol (the amount of moles in the solution)
moles= mass / molar mass
Therefore, mass = moles X molar mass
=0.025 x 106
2.65g

Hope this helps