Nature of Solutions (chapter 5 and 7.1) Flashcards
What two parts make up a solution?
Solute and solvent
What is a solute?
The thing being dissolved in a solution.
What is a solvent?
The thing doing the dissolving (solute dissolved in). (eg. water)
What does the level of conductivity in a solution depend on?
It depends on how many ions are present in the solution.
What is a strong electrolyte? How many solute particles break apart into ions? Name 3 things that this includes.
A solution that conducts electricity very efficiently. (aq)
- all solute particles break apart into ions (high solubility)
- includes strong acids, strong bases, and soluble salts
What is a weak electrolyte? How many solute particles break apart into ions? Name 2 things that this includes.
A solution that conducts electricity only slightly.
- Few solute particles create ions
- includes weak acids and weak bases
What is a nonelectrolyte? How many solute particles break apart into ions? Name something that this includes.
A solution that does not conduct electricity.
- No solute particles create ions
- includes soluble but nonionic compounds (eg. sugar, ethanol)
What is the VESPR shape of water? What angle does this shape form?
It is bent/angular/v-shaped, forming a 105 degree angle.
Why can water dissolve many substances?
Because of its polarity (oxygen is the slightly negative end because of its higher electronegativity, and hydrogen is the slightly positive end).
What is hydration? Explain water’s attraction to cations/anions.
Hydration is the interaction between the dissolving molecules and water molecules. Positive ends of water molecules are attracted to anions, and the negative ends of water molecules are attracted to cations.
What is dissociation? Do ionic compounds dissolve completely?
Dissociation is when an ionic compound dissolves in water and breaks into cations and anions. Ionic compounds do not all dissolve completely because of attractions between different ions/attraction between ions and water molecules.
Describe the part of Arrhenius’ theory about bases.
- bases are all hydroxide compounds
- bases dissociate into cations and OH
- OH is responsible for basic properties
- OH reacts with H to form water
Describe the part of Arrhenius’ theory about acids.
- acids only appear when hydrogen containing compounds dissolve in water (aq)
- dissociates into H and negative ions
- H responsible for acidic properties
Can water dissolve substances that don’t create ions?
Yes
What is ionization?
When a neutral atom or molecule is changed to an ion (assumed water solvent).
Discuss “like dissolves like” using water.
Molecules with an O-H bond like water, dissolve in water because of polarity. Nonpolar substances (eg. fat) do not dissolve in water. Nonpolar dissolves nonpolar and polar dissolves polar.
What is concentration?
The ratio that compares the quantity of solvent and quantity of solute.
When both substances in a solution are liquid, which is the solvent, and which is the solute?
The one with the largest volume is the solvent.
Percent by volume
- can be shown as % V/V (mL/100mL)
- percent by volume of the solute per volume of solution
- % volume = volume of solute / volume of solution x 100
Percent by mass/volume
- can be as % m/v (g/100mL)
- percent by mass of solute per volume of jump
- % mass/vol = mass of solute / volume of solution x 100
Percent by mass
- can be shown as % m/m (g/100g)
- percent by mass of solute per mass of solution
- % mass = mass of solute / mass of solution x 100
Parts per million
- special case of % mass
- % m/m x 10^6
- 1 ppm = 1 mg / kg
Amount concentration
C = n / v
- C - mol/L
- n - mol
- v - L
True or false: all ionic compounds are strong electrolytes.
True
What happens when 2 solutions are mixed?
the free ions float and collide randomly
What is a precipitation reaction?
When an ionic compound is insoluble in water.
True or false: if no insoluble compound forms, no reaction has occurred.
True
What are spectator ions?
Free ions not involved in a chemical reaction (do not form a precipitate/solid).
What is a net ionic equation?
- All spectator are cancelled out (the ones that don’t form a solid)
- only includes species active in the chemical reaction (form a precipitate)
- cancel out spectators on both sides of the equation
Ion concentration can be calculated using _________.
Stoichiometry
- mole ratio found in dissociated balanced equation
Describe a standard solution.
- a solution whose concentration is known (accurate [ ])
- precise measurements of solute mass and solvent volume are vital
- once a standard solution is obtained, it can be diluted to the required molarity
What is a stock solution?
A concentrated solution that can be separated into samples and diluted. They are usually standard solutions. When solvent is added to a sample of stock solution we have a dilution.
What is a dilution? What increases? What stays the same? What decreases?
A dilution is when water is added to a stock solution to decrease the concentration to a desired level.
- Volume increases
- moles stays the same
- molarity/concentration decreases
What is the formula for “moles concentrated = moles dilute”
CiVi = CfVf
- make sure units are consistent
-
Describe surface area and its relation to dissolution.
- SA refers to how much solute is exposed to solvent
- where dissolution occurs
- the more finely divided the solute is, the greater the SA and the more quickly it dissolves
Agitation (stirring) (2 points)
- increases rate of dissolution (solute evenly dispersed)
- brings fresh solute in contact with the solvent molecules
How does diffusion compare to dissolution?
- slower
- lower particle velocity
- stronger attraction between particles
- temperature increases and the rate of diffusion increases (higher kinetic energy, so solvent moves faster)
True or false: gases have higher solubility in lower temperatures, and solids have higher solubility in higher temperatures.
True
What does it mean for a liquid to be miscible? What about immiscible?
Miscible: liquids that mix well in any proportion
Immiscible: 2 liquids not soluble in each other (oil + water)
- some substances have both polar and nonpolar parts and miscible in both types of liquids
What are the 3 steps of the solubility process?
- expand solute molecules
- expand solvent molecules
- solute and solvent interact
What are the 3 things that solubility depends on?
- Characteristics of solute
- Characteristics of solvent
- temperature
Describe solubility.
For every combination of solute/solvent at a certain temperature, there is a certain amount of solute that can dissolve.
What is recrystallization?
When solute particles dissolve and some hit the surface of solute crystals and re-attach.
What is a dynamic equilibrium?
A state in which the opposing processes of dissolution and recrystallization occur at equal rates.
What is a saturated solution?
A solution that contains the maximum amount of dissolved solute (no more can dissolve, it’ll fall to the bottom)
- usually a solid will form (the excess of undissolved solid solute is evidence of a saturated solution)
What is a unsaturated solution?
A solution that contains less than maximum amount of solute.
What is a supersaturated solution?
A solution that contains more than the maximum amount of solute.
- created by heating a solution and dissolving excess solute
- must cool undisturbed
- will recrystallize quickly is seed crystal is added (additional solute)
What is a solubility value?
The amount of substance needed to make a saturated solution.
- usually in grams per 100mL of water
Name some liquids that are miscible with water.
- methanol
- ethanol
- acetic acid
- ethylene glycol
Name some liquids that are immiscible with water.
- oil
- gasoline
- benzene
- carbon disulfide
