Chapter 5 - Solutions

An aqueous solution involves what as its solvent?

Water

When sugar is dissolved into lemonade, which one is the solute?

The sugar

What does it mean when a solution has become saturated?

Maximum amount of solute that can be dissolved has been reached in the solution

What does supersaturation refer to?

When solution contains more solute than what is normally found in a saturated solution at equilibrium

What two variables can be manipulated in order to obtain supersaturated solutions?

Pressure or temperature is typically manipulated

Does solubility of solids in liquids increase or decrease with temperature?

Solubility increases with temperature

Does solubility of gases in liquids increase or decrease with temperature?

Solubility of gas decreases with temperature, as gases become more volatile, causing them to be less soluble

Does solubility of gases in liquids increase or decrease with pressure?

A gas will become more soluble in a liquid when the pressure is increased

When you have a salt consisting of a soluble ion and an insoluble ion, say for example NaOH, is it soluble?

Yes. The soluble ion 'overrides' the insoluble ion so that the overall compound is soluble

What is the formula for molarity?

Molarity = moles of solute/litres of solution

What is the formula for molality?

Molality = moles of solute/kg of solvent

Which one is independent of temperature and pressure, molarity or molality?

Molality

What is the formula for mole fraction in a solution?

Mole fraction of solute = moles of solute/total moles in solution

What is the mole fraction for hydrogen in H2O?

2/3

What is the mole fraction of carbon in CH4?

1/5

Does mole fraction have units?

No, because it is simply a ratio between moles of solute and total number of moles in the solution

What is the formula for normality?

Number of mole equivalents (n)/litre of solution

How do you determine mole equivalents for an acid?

Determine the number of H+ ions that can be dissociated per molecule. HCl can dissociate one, while H2SO4 can release two ions

How do you determine mole equivalents for a base?

Determine the number of OH- ions that can be dissociated per molecule

What are colligative properties?

Properties that depend on the amount of solute particles in the solution rather than the identity of those particles

What is vapor-pressure depression defined as?

The pressure exerted by the gaseous phase of a liquid that evaporated from the exposed surface of the liquid

What does a lower vapor pressure correspond to relative to boiling point?

Lower the vapor pressure, higher the boiling point.

If a solution has a high vapor pressure, does this suggest that the substance will evaporate more easily?

Yes

Does dissolving solute into a solvent increase or decrease entropy for the solution overall?

Increase entropy, as the added solutes make it more difficult for the solution to reach boiling point. A solution with dissolved solute requires greater energy input in order to boil

Boiling point of a liquid occurs at the temperature when the vapor pressure of the solution is equal to what?

The atmospheric pressure over the solution

What vapor pressure is needed in order to boil a solution at sea level with an atmospheric pressure of 760 mmHg?

760 mmHg

Does boiling point increase or decrease as elevation rises?

Decrease, since at a higher elevation, there is a lower atmospheric pressure

The addition of nonvolatile solutes to a solution lowers what type of pressure?

Lowers vapor pressure of the solution due to interference with the evaporation of solvent molecules.

When calculating boiling point elevation, what does the van't Hoff factor refer to?

The number of particles the solute breaks into when it dissolves

How does the addition of solute decrease the freezing point of pure solutions?

When solutes are added, it interferes with the efficient arrangement of molecules into an orderly and tightly packed array. As such, a lower temperature is needed to attain freezing point

What is the formula for calculating osmotic pressure?

Π= MiRT.

Where Π is osmotic pressure in atm, M is the molarity of the solution, i is the van 't Hoff factor, R is the universal gas constant, and T is the temperature in Kelvin

What are the units for the universal gas constant with the value 8.314?

J / (mol K)

What are the units for the universal gas constant with the value 0.08206?

(L atm) / (mol K)

What is a non-colligative property?

Properties that depend on the identity of solute particles in the solution rather than the amount of those particles

Is color a colligative or non-colligative property?

Non-colligative

Is surface tension a colligative or non-colligative property?

Non-colligative

Is vapor pressure depression a colligative or non-colligative property?

Colligative

Is viscosity a colligative or non-colligative property?

Non-colligative

Is boiling point elevation a colligative or non-colligative property?

Colligative

Is freezing point depression a colligative or non-colligative property?

Colligative

Is solubility of a solute a colligative or non-colligative property?

Non-colligative

Is osmotic pressure a colligative or non-colligative property?

Colligative

Which intermolecular forces contribute to the dissolution of a solute in a solution?

Dipole-dipole, ion-dipole, Van der Waals, and hydrogen bonding

What is the strongest intramolecular force?

Ion-ion

What is the weakest intermolecular force?

London dispersion (Van der Waals)

The intermolecular forces being broken in solutes are replaced with equal, stronger, or weaker intermolecular forces with the solvent?

Equal or stronger intermolecular forces between solvent and solute

What does the 'like dissolves like' rule of thumb refer to?

Solutes are more readily soluble in solvents that have similar polarity

Does pure water conduct electrical currents?

It does not, since the concentration of hydronium and hydroxide ions are very limited. In addition, there are no electrolytes (e.g. salts) in pure water that can help conduct electrical currents

What must be added to form conductive solutions?

Electrolytes

What property is needed to be considered a strong electrolyte?

The solute must dissociate completely into its constituent ions. (E.g. NaCl)

Is sugar considered a strong electrolyte?

No, as it does not dissociate and form ions in aqueous solutions

Are salts containing NH4+ soluble or insoluble?

Soluble

Are salts containing NO₃⁻ soluble or insoluble?

Soluble

Are salts containing Cl-, Br-, I- soluble or insoluble?

Soluble, except with Ag+ and Pb+

Are salts containing SO₄²⁻ soluble or insoluble?

Soluble, except with Group 2 metals

Are salts containing PO₄³⁻ soluble or insoluble?

Insoluble, except with alkali metal cations and NH4+

Are salts containing OH⁻ soluble or insoluble?

Insoluble, except with salts with alkali metal cations and NH4+, Ca2+, Sr2+, and Ba2+