Which Formula would I use?

Question

It took 12.5 mL of 100 mol/L Ca(OH)2 to neutralize 20.0 mL of HCl
Find the concentration of the unknown...
i was thinking i would use C1V1 = C2V2...correct?...and by using that i got the answer of 62.5 is that also correct?....last question...is this correctly neutralized?

Ca(OH)2 + HCl -> CaCl + H(OH)2

Answer 1

The correct reaction is:
Ca(OH)2 + 2HCl -> CaCl2 + 2H2O.
The formula you used is basically correct, but you have to consider the ratio 2:1 for HCl in respect to Ca(OH)2

Answer 2

No, the proper formula is:

a1C1V1=a2C2V2

where a1,a2 is the valence (number of H+ or OH- per molecule) of the acid and base.

[the actual formula is N1V1=N2V2, where N is normality; N=aM or N=aC depending on which symbol you use for concentration that is expressed in mol/L)
for HCl a=1 and for Ca(OH)2 a=2.

Do the math yourself. By the way, I agree with the answer which highlighted the fact that 100 M Ca(OH)2 is unrealistic. Check that you've got the right numbers.

Answer 3

The unknown concentration is not 62.5 mol/L but rather 125 mol/L. To arrive at the answer, you need to calculate for the amount of OH- that was used. By stoichiometry 1H+ would be neutralized by 1OH-, i.e. moles OH- calculated = moles H+ neutralized. Divide the moles H+ by 20 x 10^-3 liters to get the concentration of HCl.

Your answer should be 125 mol/L.

Also, your equation is not balanced: Ca(OH)2 + 2HCL --> CaCl2 + 2H2O

Answer 4

BTW, the highest molarity of HCl is 12 M, and I seriously doubt you could make 100 M Ca(OH)2.

Answer 5

yup it is right dude! buth the equztion is not balanced properly!
it shoul be
Ca(OH)2 +2HCl ===> CaCl2 + 2H2O
the valency of calcium is 2 and hence it can not form the compound CACl and has to form CaCl2 .

Answer 6

The molarity formula is correct: M1V1 = M2V2. However, your balanced equation should look like this:

Ca(OH)2 + 2HCl --> CaCl2 + 2H2O