GenChem 2 Exam 1

chapter 13 and 14

Solvent-solvent interactions

interactions between the water molecules, interactions involving dipole-dipole attractions

solute-solute interactions

interactions involving ion-ion attractions. ex) interactions between ions of sodium chloride

solute-solvent interactions

ex) between chloride ions and hydrogen atoms of water molecules.

ex) between sodium ions and oxygen atoms of water molecules.

KF, LiCl, NaBr

Which substances are most likely to dissolve in water?

C8H18

KF

LiCl

NaBr

C6H6

Hydrogen bonding between water molecules

The dissolution of water in octane (C8H18) is prevented by:

solvation

Hydration is a specific example of the phenomenon:

miscible

Pairs of liquids that will mix in all proportions are called:

no

Will two ionic solids with different lattice energies have the same solubility in water?

yes, very soluble.

Will an ionic compound with a very negative deltaH sol’n be soluble in water?

deltaH solvent and deltaH solute

Which terms are positive always?

deltaH solvent, deltaH solute, deltaH mix

5g

The solubility of CaCl₂ in water is 25g per 50 mL of H₂O. How many grams of CaCl₂ will dissolved to form a saturated solution in 10 mL of water?

46g

The solution on the left was formed by dissolving 170 g of the salt in 100 mL of water at 100 ∘C and the slowly cooling it to 20 ∘C. Because the solubility of sodium acetate in water at 20 ∘C is 46 g per 100 mL of water, the solution is supersaturated. Addition of a sodium acetate crystal causes the excess solute to crystallize from solution. How much sodium acetate is in the 3rd beaker?

5.9 atm

On a clear day at sea level, with a temperature of 25 °C, the partial pressure of N2 in air is 0.78 atm and the concentration of nitrogen in water is 5.3×10−4 M. When the partial pressure of N2 is ________ atm, the concentration in water is 4.0⋅10−3 M.

weak solvation of Na⁺ and Cl^- by C₆H₆

The principal reason for the extremely low solubility of NaCl in benzene (C₆H₆) is the ________.

3.53

A solution is prepared by dissolving 15.0 g of NH₃ in 250.0 g of water. The density of the resulting solution is 0.974 g/mL. The molality of NH₃ in the solution is ________ m.

M (molarity)

Do you multiply by density for M or m?

2.45 M

What is the molarity of sodium chloride in solution that is 13.0% by mass sodium chloride and that has a density of 1.10 g/mL?

2.12×10^−5

At 30 ∘C the density of water is 0.995 g/mL and the solubility of oxygen gas is 1.17 mmol per liter of water. At this temperature, what is the mole fraction of O2 in a saturated solution?