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