How many moles of HCl are there in 50cm^3 of 0.4 mol dm^-3 solution?



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Posted on (Answer #1)

Concentration of the solution is measured as the number of moles of solvent over the volume of the solution. 

Concentration = moles HCl/Volume of solution

The key in solving this problem is to make the units of the volume the same.

either you convert cm^3 to dm^3 or vice versa.

**in this case it is easier to convert cm^3 to dm^3

1cm^3 = 0.001 dm^3

50cm^3 x (0.001dm^3 /1cm^3) = 0.05 dm^3 = volume


now we go to our original formula:

Concentration = moles HCl/ volume solution

now we are looking for the moles of solute so we transform the equation to this:


moles HCl = concentraction x volume

                = 0.4 moles/dm^3  x 0.05 dm^3

                = 0.02 moles HCl



Hope this helps:)

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