What mass of #Cr(NO_3)_3*9H_2O# is required to make a #100*mL# volume of a solution that is #2.00xx10^-3*mol*L^-1# with respect to #Cr^(3+)#?

1 Answer
May 28, 2017

Answer:

We need a mass of approx...#0.8*g#

Explanation:

We use the relationship, #"Concentration"="Moles of solute"/"Volume of solution"#,

and thus to get the #"moles of solute"#, we take the product............

#"Moles of solute"="Concentration"xx"Volume"#

#=100.0*mLxx10^-3*L*mL^-1xx0.0200*mol*L^-1#

#=2.000xx10^-3*mol#.

And this represents a mass of...............

#=2.000xx10^-3*molxx400.15*g*mol^-1=0.800*g#.

Note that this question has been poorly specified. When you say #"chromium nitrate nonahydrate"# I have ASSUMED that you mean the #Cr(+III)# hydrate, #Cr(NO_3)_3*9H_2O#, whose formula mass is #400.15*g*mol^-1#.