Calculate the molar mass of naphthalene, the organic compound in mothballs, if a solution prepared by dissolving 5.00 g of naphthalene in exactly 100 g of benzene has a freezing point 2.0°C below that of pure benzene. (Kf of benzene is 5.12°C/m.)

Answer : The molar mass of naphthalene is, 128 g/mol

Explanation :  Given,

Molal-freezing-point-depression constant for benzene =

Mass of naphthalene (solute) = 5.00 g

Mass of benzene (solvent) = 100 g  = 0.100 kg

Formula used :  

where,

= change in freezing point  =

= freezing point of solution

= freezing point of benzene

i = Van't Hoff factor = 1 (for naphthalene electrolyte)

= freezing point constant for benzene =

m = molality

Now put all the given values in this formula, we get

Therefore, the molar mass of naphthalene is, 128 g/mol

answer; /// i do believe that the correct answer is (c)nuclear bond

when the volume of gas is   changed from   717.73 ml   to 852 ml   the temperature will   change   from 315   c to 452   c

    calculation

this is calculated using the charles law formula

that is,   v1/t1 = v2/t2

          v1=?

        t1 = 315 c   into   kelvin = 315 +273 = 588 k

        v2 = 852   ml

        t2 = 425c + 273 =698 k

make v1   the subject of the formula ( by   multiplying both side by t1)

  v1=( v2 xt1) / t2

v1= (852 ml   x 588 k)/ 698 k= 717.73 ml