Answered

What is the percent mass/volume and molarity of sodium chloride solution, if 2.0grams of salt is collected by evaporating from 30.0ml of sodium chloride solution?

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Imenid
M(NaCl)=M(Na)+M(Cl)
            =23+35
            =58 g/mol
n=m/M   n=c.v    ρ=m/v 
m=2g    v=30ml=0.03l
molarity of sodium chloride is:
n=m/M
   =2/58
  =3.4.10(-2)mol
the percent mass/volume is:
ρ=2/0.03
  =2/3 10^2 g/l