Simple Dilution Problem: Calculating Final Concentration (M)

[Shafty]

This problem seems simple enough, yet my professor says my answer is incorrect. Here is the problem.

1 ml of a 0.10 M solution of HCL is added to 21 ml of distilled water. What is the final concentration of the solution (M)?

Im going to use the equation

C1*V1=C2*V2

Where C1 is the initial concentration (M) and C2 is the final Concentration, and V1 is initial Volume, and V2 is final volume

If I add 1ml of HCl to 21ml of H2O, I will have 22ml of solution. This is V2, therefore

C1V1/V2=C2

(0.1M)(1ml)/(22ml)=C2

C2= 0.0045 M

What am I overlooking?

Thanks in advance.

 

[Ygggdrasil]

Looks good to me.

 

[Borek]

Perhaps s/he is nitpicking on the significant figures.

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