# chemistry pls help

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If 10.0 mL of 1.0M HCl is added to 90 mL water, what is he concentration of the new solution?
What is the pH of this solution?
If the solution is titrated by 0.500M
Ca(OH)2, how much volume (ml) of NaOH necessary? Need help pls.

• chemistry pls help -

sorry the chemical reaction is:
Ca(OH)2 (aq) + 2HCl(aq)= 2H2O(l)+CaCl2(aq)

• chemistry pls help -

Who knows what the new concn is? This is a fairy tale problem because it ASSUMES that the volumes are additive. They are not; however they are very close to it in this case so we will assume the total volume is 100 mL
Use c1v1 = c2v2
c = concn
v = volume

1.0M x 10mL = c2*100
C2 = (1.0 x 10/100) = ?

pH = -log(H^+)

mols HCl = M x L = ?
Convert mols HCl to mols Ca(OH)2. That's mols Ca(OH)2 = 1/2 mols HCl (from the coefficients in the balanced equation). Then
M Ca(OH)2 = mols Ca(OH)2/L Ca(OH)2. You know mols and M, solve for L and convert to mL).

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