Chem 1220: Lecture 5 Flashcards
(12 cards)
What drives colligative properties?
Colligative properties are driven primarily by entropy, not enthalpy
What happens to vapor pressure when a nonvolatile solute is added to a volatile solvent?
The vapor pressure decreases
What are colloids?
Mixtures where one substance is dispersed throughout another substance, with particle sizes between those of solutions and suspensions
What is the difference between hydrophilic and hydrophobic colloids?
- Hydrophilic (water-loving) colloids: Particles remain suspended due to attractive forces with water
- Hydrophobic (water-fearing) colloids: Particles will separate from water unless stabilized
What are the four variables that impact reaction speed?
- Physical state of reactants
- Concentration of reactants
- Temperature of the reaction
- Presence of a catalyst
How is reaction rate measured?
By measuring the change in amount of reactant or product as a function of time
What is the general formula for average reaction rate?
Average rate = -(1/a)Δ[A]/Δt = -(1/b)Δ[B]/Δt = (1/c)Δ[C]/Δt = (1/d)Δ[D]/Δt
For reaction: aA + bB → cC + dD
Why don’t H₂ and O₂ instantaneously explode?
Because energy input (activation energy) is needed to break bonds before forming new ones
What is the difference between kinetics and equilibrium?
- Kinetics: Deals with the path and speed between reactants and products
- Equilibrium: Deals with the balance of reactants and products given unlimited time
What are the different types of colloids?
- Aerosol (gas in gas): Fog, smoke
- Foam (gas in liquid): Whipped cream
- Emulsion (liquid in liquid): Milk
- Sol (solid in liquid): Paint
- Solid foam (gas in solid): Marshmallow
- Solid emulsion (liquid in solid): Butter
- Solid sol (solid in solid): Ruby glass
How do you calculate reaction rates with different stoichiometric coefficients?
Divide the rate by the stoichiometric coefficient. For example, if 2A → B, then rate of B formation = ½ × rate of A disappearance
What is an emulsifier?
A substance that helps stabilize an emulsion by preventing the separation of phases (example: lecithin)
