Mod 13 Flashcards
(20 cards)
What is the minimum energy required for a chemical reaction called?
Activation energy
Activation energy is the energy that must be overcome for a reaction to occur.
How does increasing temperature affect reaction rates?
Increases reaction rates
Higher temperature results in more kinetic energy, leading to faster reactions.
What effect does increased reactant concentration have on reaction rates?
Raises collision frequency
More reactant molecules lead to more frequent collisions.
What role do catalysts play in chemical reactions?
Provide an alternative pathway with lower activation energy
Catalysts increase the rate of reaction without being consumed.
What does it mean when a chemical reaction is described as reversible?
Forward and reverse processes occur simultaneously
Reversible reactions can achieve equilibrium.
What indicates that a chemical reaction is reversible in notation?
Double arrows (⇌)
Double arrows signify that reactants can form products and vice versa.
What is dynamic equilibrium?
Both forward and reverse reactions continue to occur
At dynamic equilibrium, the concentrations of reactants and products remain constant.
What is the equilibrium constant (Kc)?
Relates product and reactant concentrations at equilibrium
Kc provides a numerical value indicating the ratio of products to reactants.
What does a large Kc (>~10^2) imply about a reaction?
Product-favored
A large Kc indicates that at equilibrium, products are favored over reactants.
What does a small Kc (<~10^-2) imply about a reaction?
Reactant-favored
A small Kc indicates that at equilibrium, reactants are favored over products.
What is the expression for Kc for the reaction N2 + 3 Cl2 ⇌ 2 NCl3?
Kc = [NCl3]^2 / ([N2][Cl2]^3)
The concentration of products is raised to their coefficients over the concentration of reactants.
What happens to the equilibrium when a stress is applied, according to Le Châtelier’s Principle?
The system shifts to relieve that stress
Stresses can include changes in concentration, pressure, volume, or temperature.
What effect does adding reactant have on equilibrium?
Drives the reaction toward products
Adding reactants increases their concentration, shifting the equilibrium to the right.
What effect does decreasing volume have on gaseous equilibria?
Shifts toward fewer moles of gas
A decrease in volume increases pressure, favoring the side with fewer gas molecules.
How do endothermic reactions respond to temperature changes?
Absorb heat (heat as reactant)
Increasing temperature favors the forward reaction in endothermic processes.
How do exothermic reactions respond to temperature changes?
Release heat (heat as product)
Raising temperature favors the reverse reaction in exothermic processes.
What is the Kc expression for the reaction Ni(s) + 4 CO(g) ⇌ Ni(CO)₄(g)?
Kc = [Ni(CO)₄] / [CO]^4
The concentration of solid Ni is omitted from the Kc expression.
If Kc = 1 × 10⁻¹², does the equilibrium favor products or reactants?
Reactants
A very small Kc indicates that reactants are favored at equilibrium.
What is the effect of adding HF to the system H2 + F2 ⇌ 2 HF?
Shifts to reactants
Adding products shifts equilibrium to the left.
In the reaction 2 NO2 ⇌ 2 NO + O2 (+ heat), what happens when temperature is raised?
Shifts toward products (right)
Raising temperature favors the endothermic direction.
