How much 5.0 M HNO3 is needed to make 225ml of 1.0M HNO3?

1 Answer
Truong-Son N.
May 17, 2018

Well, the easy way to do this is to realize that solute concentration and solution volume are inversely proportional.

Since you want to go from #"5.0 M"# to #"1.0 M"# concentration, and you want #"225 mL"# of the resultant solution, you want to get #1/5# of the concentration. Thus, you should get that #"225 mL"# is five times the volume you started with...

#-> color(blue)"45 mL"# of #"5.0 M"# #"HNO"_3#

Again, by starting at #"45 mL"#, #"225 mL"/"45 mL" = 5# times the volume, which results in one-fifth the concentration, and #"1.0 M" = 1/5("5.0 M")#.

I suppose if you wanted to do it the hard way...

#M_1V_1 = M_2V_2#

#V_1 = M_2/M_1 V_2#

#= "1.0 M"/"5.0 M" cdot "225 mL" = "45 mL"# #color(blue)sqrt""#

But then, just using the equation, how do you know you don't have the concentration ratio upside-down? What happens to concentration and volume in a dilution?

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