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

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.