1) You dissolve 19.020 grams of substance X (whose molar mass is 62.360 g/mol) i

Question

1) You dissolve 19.020 grams of substance X (whose molar mass is 62.360 g/mol) in 2.590 L of water (whose molar mass is 18.02 g/mol). The density of water at this temperature is .9750 g/mL. Calculate the mass percent of substane X.

2) A solution contains 27.79 grams of NaCl in .909 kg water at 25 degrees celcius. What is the vapor pressure of the solution? (The molar mass of NaCl is 58.44 g/mol. The molar mass of water is 18.02 g/mol.) and (The vapor pressure of water is 23.7 torr at 25 degrees Celcius

3)The freezing point of benzene is 5.5 degrees celcius. What is the molar mass of a nonionizing solute if 1.80 grams of the solute added to 24.81g of benzene lowers the freezing point to 3.22. The Kf of benzene is -5.12 degrees C/m.

Explanation / Answer

Ans 1 :

Density = mass / volume

so mass of water = density x volume

= 0.9750 x 2.590

= 2.52525 kg

or 2525.25 grams

So the total mass of solution = 19.020 + 2525.25 = 2544.27 grams

Mass percent of X = ( mass of X / total mass of solution) x 100

= ( 19.020 / 2544.27) x 100

= 0.75%

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