1. a chemisty is given a white solid that is suspectedof being pure cocaine. whe

Question

1. a chemisty is given a white solid that is suspectedof being pure cocaine. when 1.22g of the solid is dissolvedin 15.60g of benzene the feezing point is lowered by 1.32oC. calculate the molar mass of the solid. the molal freezing point constant of rbenzene is5.12oC/m 2. how many molecules of sucrose(table sugar),C12H22O11, dissolved in450.0g of water are needed to make a 1.75msolution? 1. a chemisty is given a white solid that is suspectedof being pure cocaine. when 1.22g of the solid is dissolvedin 15.60g of benzene the feezing point is lowered by 1.32oC. calculate the molar mass of the solid. the molal freezing point constant of rbenzene is5.12oC/m 2. how many molecules of sucrose(table sugar),C12H22O11, dissolved in450.0g of water are needed to make a 1.75msolution?

Explanation / Answer

1.         Tf = Kf x molality of the solution          1.320 C = 5.12 0C x 1.22 gm/ M gm / mole x 1000 / 15.60 gm              Molar mass of the solid = 303.34 gm / mole 2.          Number ofmoles = molality x weight of the solvent ( Kg )                                      = 1.75 m x 0.450 Kg                                       = 0.7875 moles          We Knowthat 1 mole constitutes of 6.023 x1023 molecules                              0.785 moles contains   4.74311 x 1023molecules.

  

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