Solutions Flashcards
What is required for a chemical reaction to take place?
Collision energy: activation energy, the minimum value of energy required for the reaction to take place
Collision geometry: modules must collide with the correct orientation
What is a exothermic reaction?
Reaction where heat/energy is released
What is needed for an exothermic reaction to take place?
Need to give it a bit of energy
How much energy will the product of an exothermic reaction have?
Less than what it started out with
How much energy will the product of an endothermic reaction have?
More energy than the reactants
Which have higher activation energy, exothermic or endothermic reactions?
Endothermic reactions
What factors affect rate of reaction?
Temperature: increase increases rate of reaction as particle kinetic energy is increased
Concentration: increase increases rate of reaction due to increase in correctly oriented collisions
Particle size: decrease in size increases rate of rector due to increase in surface area
Pressure ( only gasses) & volume: increase pressure or decrease volume increases rate of reaction
Catalyst: reduces activation energy
Definition of equilibrium
At equilibrium the rate of the forward reaction = the rate of the reverse reaction
What are the conditions for equilibrium reactions?
They are dynamic
Must occur in a closed system
Concentrations must be constant
No macroscopic changes take place
What is the equilibrium constant?
Constant value for a certain reaction at a certain temperature
Formula for equlibrium constant
Google the answer
What is importat to remember when calculating equilibrium constant?
Units
How do you figure out what direction a reaction will favor?
Calculating the possible equilibrium constant. If it is lower the one given the forward reaction wil be favored, if it is high the backwards will se favored
What are the 3 possibilities for the solution of Q in comparison to k?
Q = k, equilibrium
Q > k, reaction go left, reverse reaction is favored
Q < k, reaction go right, forward reaction is favored
What does Le Chatelier’s principle state?
If we change something in a reaction it will adjust so equilibrium is reached again
How does added reactants change the equilibrium?
Reaction goes right, forward reaction is favoured
How does added products change the equilibrium?
Equilibrium goes left, reverse reaction is favoured
How does increase in pressure (decrease in volume) change the equilibrium? (Gasses only )
Side with less molecules is favoured
How does decrease in pressure (increase in volume) change the equilibrium? (Gasses only)
Side with more molecules is favoured
How does increase in temperature of an endothermic change the equilibrium?
Increase in product, reverse reaction is favoured
How does increase in temperature of an exothermic change the equilibrium?
Decreases product & forward reaction is favoured
What happens to the equilibrium constant k when temperature is changed?
It changes as well
What is delta H in an endothermic reaction?
Positive
What is delta H in an exothermic reaction?
Negative
What effect does a catalyst have on the equilibrium?
It is reached faster, no effect on K (equilibrium constant)
What is a homogenous mixture?
Uniform mixtures, no distinguishable components
Ex : salt water
What is a heterogenous mixture?
None uniform mixtures, distinguishable components
Ex: blood
Definition of solution
Homogenous mixture of 2 or more substances
What are the 2 components of a solution?
Solvent & solute
What is the solvent?
The thing that dissolves the other substance, what takes up the volume, larger mass or more moles
What is the solute?
The thing that gets dissolved
What phases can solutions be?
Gas, liquid or solid
Definition of solubility
The amount of solute that will dissolve per volume of solvent
What does it mean when something has a higher solubility
More will be dissolved
What is solubility impacted by?
Molecular structure: some chemicals dissolve more than others
Pressure (only for gas): increase in pressure increases gas solubility in a liquid
Temperature: increased temperature decreases gas solubility in liquid. Increases in temperature increases solid/liquid solubility in liquid
Rule about solubility
Like dissolves like
Will a polar solute dissolve in a polar solvent?
Yes
Will a non-polar solute dissolve in a non-polar solvent?
Yes
Will a polar solute dissolve in a non-polar solvent?
No
What is the saturation point?
Where the maximum solubility is reached
What does saturation point depend on?
Temperature, pressure (gas) & chemical structure
What happens to the freezing, melting & boiling point when adding a solute to water?
Decease in freezing & melting point, increase in boiling point
What happens if you add salt to ice?
Makes it easier to melt
What happens to the boiling and freezing point if you add salt to water?
Make it harder to freeze & require higher temperature to boil
What is evaporation used for?
Separate a dissolved solid from a liquid, liquid is lost & solid retained
What is distillation used for?
Separating 2 liquids
How does distillation work?
Heating & cooling is used to separate 2 liquids, relies on a difference in boiling point
What is filtration used for?
Separating solid from a liquid, only work on heterogenous mixtures
What is chromatography used for?
Separating liquid-liquid, solid-liquid, solid-solid
Rough steps of chromatography
Mixture is dissolved into a mobile phase (gas or liquid)
Mobile phase flows through the chromatography system
Mixture is separated onto the stationary phase (a piece of paper)
What is centrifugation used for?
Separate solids from liquids or liquids from liquids, has to be a heterogeneous mixture
What is the separation Method of chromatgraphy?
Polarity, size, binding affinity, boiling point or charge
What is crystallization used for?
Separating a solid from a liquid in a homogeneous mixture
What is important in order to be able to use crystallization?
The solid should have a crystalline structure
What principle is crystallization based on?
That solubility of a solid in a liquid generally increases with temperature increase & decreases with a temperature decrease
Is crystallisation a physical or chemical change?
Physical
