Answer:
50 mL of 12M HCl should be added into 100 mL of water to produce a 4M solution.
Explanation:
According to law of dilution-
[tex]C_{1}V_{1}=C_{2}V_{2}[/tex]
where [tex]C_{1},C_{2},V_{1}[/tex] and [tex]V_{2}[/tex] are initial concentration, final concentration, initial volume and final volume respectively.
Here, [tex]C_{1}=12M[/tex] , [tex]C_{2}=4M[/tex] , [tex]V_{1}=50mL[/tex]
So, [tex]V_{2}=\frac{C_{1}V_{1}}{C_{2}}[/tex] = [tex]\frac{(12M)\times (50mL)}{(4M)}[/tex] = 150 mL
Hence, final volume of HCl solution should be 150 mL.
So, volume of water needed = (150-50) mL = 100 mL
Therefore 50 mL of 12M HCl should be added into 100 mL of water to produce a 4M solution.
