Question

How much BaCl2 would be needed to make 250 mL of a solution having same concentration of Cl^- as the one containing 3.78g of NaCl per 100 mL?

Answer 1

3.78 g NaCl/100 mL = 37.8 g/L solution and that's how many mols.
37.8/molar mass = approx 0.6 mols/L but you need answer than this estimate. This makes (Cl^-) = approx 0.6M

You want to make 250 mL of BaCl2 and since BaCl2 has 2 Cl atoms/1 Bacl2 molecule, you only need 0.3 M; therefore,
mols BaCl2 needed = M x L = ?
grams BaCl2 = mols BaCl2 x molar mass BaCl2.

Answer 2

16.8 gm

Answer 3

gand maras bsdwalo tumhari maa ki chut mein mein apna pole ghusaunga