Calculate the molarity of the HCl solution if 25.00ml of the acid are required to neutralize 1.00g of each of the following

1) KOH

2)Ca(OH)2

I calculated the molar mass of KOH which was 56.11
Then I took 1.00g/56.11 = 0.0178mol
To find out the molarity I did 0.0178/0.025=0.7128M

I just want to know what I'm doing is right.

1 answer

Yes, you are right but you need to tweek your thinking a little.
1. You have 4 significant figures in 25.00 and 3 in 1.00g; therefore, you are allowed only 3 s.f. in the answer. Thus, your answer of 0.7128 should be rounded to three s.f. of 0.713M. Some profs will count 0.7128 M wrong.

2. The reaction is KOH + HCl ==> KCl + H2O
Therefore, you properly converted 1.00 g KOH to mols KOH. The next step is to convert mols KOH to mols HCl. In this case the ratio in the reaction is 1:1 (1 mol KOH to 1 mol HCl) and it is obvious that mols KOH = mols HCl and the conversion is automatic. I'm just bringing this up for cases when the ratio in the titration is not 1:1. In
Ba(OH)2 + 2HCl ==> BaCl2 + 2H2O
mols Ba(OH)2 = M x L
mols HCl = 2x mols Ba(OH)2
Then M HCl = mols HCl/L HCl

I'm not trying to confuse you and probably you already know all of this; I'm just trying to make sure you don't leave out that step when it is necessary.