How many moles of sodium hydroxide are needed to prepare 250 ml of a 0.85 m solution? a) 0.0034 b) 3.4 c) 210 d) 0.21

The moles  of  sodium hydroxide that are needed to prepare 250 ml  of a 0.85 m solution  is 0.21  Moles   ( answer D)

  calculation

moles of  sodium  hydroxide is   calculated using   moles =  molarity  x volume in liters formula

 where,

  molarity = 0.85 M  =  0.85 mol/ L

  moles = ?

 volume  = 250 ml   convert  into Liters

           that is  1 L =  1000 Ml

                       ? L=  250  ml

by cross  multiplication

=( 250 ml  x 1 L) / 1000 ml = 0.25 L

moles is therefore= 0.85 mol/l   x 0.25 L  = 0.21  moles  of sodium hydroxide

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