SCH4U EXAM REVIEW QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026
Closed vs open system - Answers Open - energy and matter can enter/exit
Closed - only energy can enter/exit
1 calorie = - Answers 4.18 J
1st law of thermodynamics - Answers Energy is conserved and cannot be created nor destroyed
Enthalpy - Answers Quantitative measure of the energy content of a subs
ΔH for exo v endothermic subs and how it appears in thermochemical eqn - Answers -ΔH for
exothermic, energy will appear on product side
+ΔH for endothermic, energy will appear on reactant side
Thermochemical eqn vs balanced chemical equation - Answers Thermochem. has energy on the
product or reactant side, B.C.E. will have it after the eqn as + or - ΔH
Molar enthalpy - Answers Enthalpy change per mole of substance.
Bond enthalpy - Answers The energy needed to break one mole of a bond
Bond breaking is ________, bond forming is _________ - Answers endothermic; exothermic
Hess's Law - Answers if a process can be represented as the sum of several steps, the enthalpy
change of the process equals the sum of the enthalpy changes of the steps
Collision theory and factors affecting rate of reaction - Answers Idea that reactions occur when two
particles collide *effectively* (sufficient energy and the correct orientation so old bonds broken and
new ones formed)
Catalyst: increases rate without direct participation (lowers activations energy, more rxns can occur)
Temperature: increased temp increases rate, lowering does the opposite (more Ek, collide more
frequently)
Surface area: increase SA increases rate (more particles colliding)
Concentration: increased conc. increases rate (more particles interacting)
Reactivity of reactants: higher reactivity increases rate (more likely to react)
Rate law formula - Answers r = k [A]^x [B]^y (exponents are determined from trial table, k is the
temp-dependent rate constant)
Orders of reaction vs overall OoR - Answers Indicates how the reaction proceeds compared to how
much of that subs. Overall is each compound's OoR added.
Rate of reaction formula - Answers rate = collision frequency x collision
effectiveness
Activated complex - Answers The point where bonds are partially formed and partially broken, max
potential energy
Rate laws are for _______ concentrations - Answers initial
Reaction mechanism and how to recognize intermediates vs catalysts - Answers The sequence of
steps for a rxn. Intermediates are produced in a reaction and used up in another. Catalysts appear the
opposite, where they're used up in one and regenerated in another.
Ksp - Answers (Ksp) describes how many ions will be present at eqm.
Arrhenius vs Bronsted-Lowry - Answers Arrhenius: acids produce H+ in soln, bases produce OH- in
soln
BL: Acids donate H+, bases accept H+
Oxyacid - Answers Protons donated
are attached to an oxygen atom.
Organic/carboxylic acid - Answers Acids with carbon atom backbone and a carboxyl group, all are
weak.
Does Ka increase or decrease as a polyprotic acid loses protons? - Answers Since Ka measures how
strong an acid is and how readily it will dissociate (release its H+), it will decrease as the acid loses
protons since it will hold onto the remaining hydrogens more and more tightly.
What is Kw? - Answers 1.0 x 10^-14, represents the [OH-][H3O+] that naturally happens in water.
Closed vs open system - Answers Open - energy and matter can enter/exit
Closed - only energy can enter/exit
1 calorie = - Answers 4.18 J
1st law of thermodynamics - Answers Energy is conserved and cannot be created nor destroyed
Enthalpy - Answers Quantitative measure of the energy content of a subs
ΔH for exo v endothermic subs and how it appears in thermochemical eqn - Answers -ΔH for
exothermic, energy will appear on product side
+ΔH for endothermic, energy will appear on reactant side
Thermochemical eqn vs balanced chemical equation - Answers Thermochem. has energy on the
product or reactant side, B.C.E. will have it after the eqn as + or - ΔH
Molar enthalpy - Answers Enthalpy change per mole of substance.
Bond enthalpy - Answers The energy needed to break one mole of a bond
Bond breaking is ________, bond forming is _________ - Answers endothermic; exothermic
Hess's Law - Answers if a process can be represented as the sum of several steps, the enthalpy
change of the process equals the sum of the enthalpy changes of the steps
Collision theory and factors affecting rate of reaction - Answers Idea that reactions occur when two
particles collide *effectively* (sufficient energy and the correct orientation so old bonds broken and
new ones formed)
Catalyst: increases rate without direct participation (lowers activations energy, more rxns can occur)
Temperature: increased temp increases rate, lowering does the opposite (more Ek, collide more
frequently)
Surface area: increase SA increases rate (more particles colliding)
Concentration: increased conc. increases rate (more particles interacting)
Reactivity of reactants: higher reactivity increases rate (more likely to react)
Rate law formula - Answers r = k [A]^x [B]^y (exponents are determined from trial table, k is the
temp-dependent rate constant)
Orders of reaction vs overall OoR - Answers Indicates how the reaction proceeds compared to how
much of that subs. Overall is each compound's OoR added.
Rate of reaction formula - Answers rate = collision frequency x collision
effectiveness
Activated complex - Answers The point where bonds are partially formed and partially broken, max
potential energy
Rate laws are for _______ concentrations - Answers initial
Reaction mechanism and how to recognize intermediates vs catalysts - Answers The sequence of
steps for a rxn. Intermediates are produced in a reaction and used up in another. Catalysts appear the
opposite, where they're used up in one and regenerated in another.
Ksp - Answers (Ksp) describes how many ions will be present at eqm.
Arrhenius vs Bronsted-Lowry - Answers Arrhenius: acids produce H+ in soln, bases produce OH- in
soln
BL: Acids donate H+, bases accept H+
Oxyacid - Answers Protons donated
are attached to an oxygen atom.
Organic/carboxylic acid - Answers Acids with carbon atom backbone and a carboxyl group, all are
weak.
Does Ka increase or decrease as a polyprotic acid loses protons? - Answers Since Ka measures how
strong an acid is and how readily it will dissociate (release its H+), it will decrease as the acid loses
protons since it will hold onto the remaining hydrogens more and more tightly.
What is Kw? - Answers 1.0 x 10^-14, represents the [OH-][H3O+] that naturally happens in water.
