Chapter 2.1: Physical Properties of Solutions

Solution

A homogeneous mixture where components are indistinguishable and evenly distributed.

Solvent (substance that dissolves) and Solute (substance being dissolved).

2 main components of a solution

Saturated solution

A solution that contains the maximum amount of solute that can dissolve at a given temperature.

Unsaturated solution

Contains less solute than it has the capacity to dissolve.

Super saturated solution

Contains more solute than is present in a saturated solution.

Solvent-solvent interaction
solute-solute interaction
solvent-solute interaction

3 types of interactions involved in Solution Formation

Exothermic

When solute-solvent attraction is stronger than solvent-solvent and solute-solute attractions (ΔHsoln < 0)

Endothermic

When solute-solvent attraction is weaker than solvent-solvent and solute-solute attractions (ΔHsoln > 0)

Concentration

amount of solute present in a given amount of solution

percent by mass
mole fraction
molarity
molality

4 common units of Concentration

Percent by mass

ratio of the mass of a solute to the mass of the solution, multiplied by 100 percent

mass of solute/mass of solution X 100%

formula of percent by mass

unitless, because it is a ratio of two similar quantities.

Unit of percent by mass

unitless, because it is a ratio of two similar quantities

Unit of mole fraction

mole fraction of component N = moles of N/sum of moles of all components

Formula of mole fraction

Molarity (M)

defined as the number of moles of solute in 1 L of solution.

mol/L

units of molarity

moles of solute/liters of solution (L)

formula of molarity

Molality (m)

is the number of moles of solute dissolved in 1 kg (1000 g) of solvent

moles of solute/moles of solvent (kg)

formula of Molality

Molality is independent of temperature, while molarity depends on solution volume, which changes with temperature.

Why is molality sometimes preferred over molarity?

1. separation of solvent molecules

2. separation of solute molecules

3. solvent molecules and solute molecules mix together

steps in solution formation

Concentration unit

A quantitaive study for a solution that requires knowing its concentration

percent by weight/weight percent

percent by mass can be also called as _______

gas

gas + gas

liquid

gas + liquid

solid

gas + solid

liquid

liquid + liquid

liquid

solid + liquid

solid

solid + solid

air

example of gas + gas

soda water (CO2 in water)

example of gas + liquid

H2 gas in pulludum

example of solid + gas

ethanol in water

example of liquid + liquid

naCI in water

example of solid + liquid

brass, solder

example of solid + solid

1.61%

A sample of 0.892 g of potassium chloride (KCI) is dissolved in 54.6 g of water. What is the percent by mass of KCI in the solution?

0.607

A mixture of gases contains 4.46 moles of Neon (Ne), 0.74 mole of Argon (Ar), and 2.15 moles of Xenon (Xe). Calculate the mole fraction of Neon.

0.375 M

A 355-mL soft drink sample contains 0.133 mol of sucrose (table sugar). What is the molar concentration of sucrose in the beverage?

0.839 M

Distilled white vinegar is a solution of acetic acid, CH3CO2H, in water. A 0.500-L vinegar solution contains 25.2 g of acetic acid. What is the concentration of the acetic acid solution in units of molarity? (I mol acetic acid = 60.052 g acetic acid)

1.26m

Calculate the molality of a sulfuric acid solution containing 24.4 g of sulfuric acid in 198 g of water. The molar mass of sulfuric acid is 98.09 g.