Assuming complete dissociation of the solute, how many grams of kno3 must be added to 275 ml of water to produce a solution that freezes at -14.5 c? the freezing point for pure water is 0.0 c and k_f is equal to 1.86 c/m

108.43 g.

Explanation:

ΔTf = i.Kf.m,

where, ΔTf is the elevation in boiling water (ΔTf = 0.0°C - (- 14.5°C) = 14.5 °C).

i is van 't Hoff factor, The van 't Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved and the concentration of a substance as calculated from its mass. For most non-electrolytes dissolved in water, the van 't Hoff factor is essentially 1.

i for KNO₃ = 2/1 = 2.

Kf is the molal freezing constant of water (Kf = 1.86 °C/m).

m is the molality of the solution.

∵ ΔTf = i.Kf.m,

∴ m = (ΔTf)/(i.Kf) = (14.5°C)/(2)(1.86 °C/m) = 3.9 m.

m = (no. of moles of KNO₃)/(mass of water (kg)) = (mass/molar mass of KNO₃)/(mass of water (kg)).

∴ 3.9 m = (mass of KNO₃ / 101.1 g/mol)/(0.275 kg).

∴  mass of KNO₃ = (3.9 m)(101.1 g/mol)(0.275 kg) = 108.43 g.

answer; protein;

in chemistry, adhesion and cohesion are attractive forces that exist between molecules. they hold the molecules together from each other. they are different in that adhesive force exists between molecules of different substance while cohesive force happens between molecules of same substance.

adhesion between water and glass causes water molecules at the edge of water and glass interface to climb up the wall in a narrow glass tube. this is called capillary action. cohesion is what gives glass its shape and causes water to form a droplet.