To find molarity
1) number of mol of solute.
Solute is HCl.
M(HCl)= 1.0+35.5 =36.5 g/mol
25g *1 mol/36.5 g = 25/36.5 mol HCl
2) Molarity is number of mole of the solute in 1 L solution.
150 mL = 0.150 L
(25/36.5 mol HCl )/(0.150 L) = 25/(36.5*0.150) ≈ 4.57≈4.6 mol/L