Question

If 31.00 mL of a dilute solution of lime water (calcium hydroxide) required 10.10 mL of 0.246 M hydrochloric acid solution for neutralization to a methyl red end point, calculate the molarity of the lime water.

Can you please explain how to do it?
Do I use M1V1=M2V2?

Answer 1

M1V1 = M2V2 is a shortcut to these problems when they are 1:1 mole ratio but ONLY then. This one is not so you must go the long way.
Write the equation.
Ca(OH)2 + 2HCl ==> CaCl2 + 2H2O

moles HCl = M x L = ??
Use the coefficients in the balanced equation to convert moles HCl to moles Ca(OH)2.
moles HCl x (1 mole Ca(OH)2/2 moles HCl) = ??moles HCl x (1/2) = xx moles Ca(OH)2.

M Ca(OH)2 = xxmoles Ca(OH)2/L Ca(OH)2.

Answer 2

Thanks soooo much!!!