Simple chemistry help needed

[Jaramide]

I need to return an asignment today and i just cant figure it out (should be a piece of cake for the people that hangs around here)

There is 10ml HCl with an unknown concentration i a beaker. You let NaOH with the concentration 0,100 mol/dm3 drip into the acid untill it is neutralized.
It takes 10,5ml NaOH to neutralize the acid.

With this you should be able to calculate the concentration of the acid or so my teacher say. And all i can do is sit here and look dumb while my brain refuses to cooperate

Could anyone help me i would owe you a life debt. If i dont get this in today i wont get a grade in chemistry [*(]

[himanshu121]

I have posted hint at http://physicsforums.com/showthread.php?s=&postid=115160#post115160

[ShawnD]

10.5mL is 0.0105L

mols of NaOH:
0.0105L x 0.1mol/L = 1.05 x 10^-3 mols NaOH

mols of HCl:
1molHCl/1molNaOH * 1.05 x 10^-3 mols NaOH = 1.05 x 10^-3 mol HCl

concentration:
(1.05 x 10^-3 mol HCl) / 0.01L = 0.105 mol/L