If molarity is in mol/dm3 2HCL+Ca(OH)2=CaCl2+2H2O Moles of ca(oh)2 = 98/1000 x 0.250 = 0.0245 moles moles of hcl = 0.049 As the 1 is to 2 ratio among them moles = molarity x volume 0.049 = molarity x 24/1000 molarity=2.042 mol/dm3 ANSWER IS 2.042 mol/dm3