15g of calcium hydroxide is dissolved in 500cm^3 of water 300cm^3 of the solution is used to neutralise hydrocloric acid of/5mol.dm^3 how do i calculate the volume of the acid

Answer 1

15 g Ca(OH)2 = ? mols.
That's 15/molar mass Ca(OH)2 = 15/74 = estimated 0.2
You used how many mols for the neutralization? That's 0.2 x (300/500) = estimated 0.12 mol Ca(OH)2.

The equation is
Ca(OH)2 + 2HCl ==> CaCl2 + 2H2O

If you neutralize 0.12 mols Ca(OH)2 it will required 0.24 mols HCl.
Then M HCl = mols HCl/L HCl. You know mols HCl and M HCl, solve for L HCl and convert to mL or whatever using you want. Check all of this.