CHEM 219 MODULE 5 COMPREHENSIVE
EXAM QUESTIONS AND CORRECT
ANSWERS GRADED A+
◉ Closed System
Answer: Is a system that exchanges only energy with its
surroundings, not matter (e.g. Putting a lid on a insulated
saucepan)
◉ System
Answer: Is the part of the universe that is being studied (e.g. a
chemical reaction can be regarded as a system)
◉ Surroundings
Answer: The rest of the universe that interacts with the system
◉ Equilibrium
Answer: The concentration of reactants and products, stay
constant but not necessarily equal. Can be obtained in a closed
system where reaction is carried out in a closed system, where no
reactant and products are lost
◉ Dynamic equilibrium
,Answer: Reactants are converted to products and products are
converted to reactants at an EQUAL AND CONSTANT rate at equal
concentrations, but always dynamic (do not end up with equal
concentrations) (DOUBLE ARROW HEAD)
◉ Static Equilibrium
Answer: occurs when all particles in the reaction are at rest and
there is no motion between reactants and products. The rates of
the forward and reverse reactions are zero. (SINGLE ARROW
HEAD)
◉ Collision Theory
Answer: for a reaction to occur, the particles must collide with
sufficient energy (activation energy EA) to break the bonds and
have the appropriate orientation to allow the new bonds to form.
◉ Characteristics of Equilibrium
Answer: 1. In a closed system - no matter enters or leaves the
system
2. Macroscopic Properties (State, colour, temperature and
pressure) stay constant
3. Concentration of reactants and products stay constant (NOT
equal)
4. Rate of forward reaction = Rate of backward reaction
◉ Differences between Static and Dynamic Equilibrium
,Answer: Static Equilibrium:
- Forward + Reverse Reaction at the same rate
- Concentrations remain constant
- Reaction has reached completion
-→
- Reactions + Product do not interact
- Non-Reversible Reaction
Dynamic Equilibrium
- Forward + reverse reactions at the same rate
- Concentration remains constant
- Reaction never reaches completion
-⇌
- Reactions + Products interact
- Reversible Reactions
◉ How to notice Dynamic Equilibrium in a graph
Answer: You can notice dynamic equilibrium when the
concentrations of both reactants and products stay constant but
dynamic.
◉ What is an example of Static Equilibrium
, Answer: For Example: C-Diamond and graphite. At room
temperature, you are not going to see either reaction taking place,
so this could be considered a static equilibrium situation.
◉ What was the aim for the: reversible and irreversible reaction
Answer: To observe the several chemical reactions and determine
whether they are reversible or not
◉ Method for the: Reversible and Irreversible Reaction
Answer: 1. Cobalt(II) Chloride Hydrated and Dehydrated
CoCl2 + 6H2O ⇌ CoCl2.6H2O
2. Iron(III) Nitrate and Potassium Thiocyanate
Fe+3(aq) + SCN(aq) ⇌ FeSCN+2(aq)
- When you increase concentration of Fe in FeSCN it suggest a
forward reaction and the darker red shows this
- When you increase concentration of SCN, in FeSCN it suggests a
forward reaction as the solution gets darker red showing that
more reactant are being used up in products
- Decrease in colour suggest decrease in colour
- The adding of Ag allows for precipitation to be formed with SCN,
therefore removing itself from FeSCN solution, showing a reverse
reaction hence the murky white
3. Burning Magnesium
2Mg + O2 → 2MgO
4. Burning Steel Wool
EXAM QUESTIONS AND CORRECT
ANSWERS GRADED A+
◉ Closed System
Answer: Is a system that exchanges only energy with its
surroundings, not matter (e.g. Putting a lid on a insulated
saucepan)
◉ System
Answer: Is the part of the universe that is being studied (e.g. a
chemical reaction can be regarded as a system)
◉ Surroundings
Answer: The rest of the universe that interacts with the system
◉ Equilibrium
Answer: The concentration of reactants and products, stay
constant but not necessarily equal. Can be obtained in a closed
system where reaction is carried out in a closed system, where no
reactant and products are lost
◉ Dynamic equilibrium
,Answer: Reactants are converted to products and products are
converted to reactants at an EQUAL AND CONSTANT rate at equal
concentrations, but always dynamic (do not end up with equal
concentrations) (DOUBLE ARROW HEAD)
◉ Static Equilibrium
Answer: occurs when all particles in the reaction are at rest and
there is no motion between reactants and products. The rates of
the forward and reverse reactions are zero. (SINGLE ARROW
HEAD)
◉ Collision Theory
Answer: for a reaction to occur, the particles must collide with
sufficient energy (activation energy EA) to break the bonds and
have the appropriate orientation to allow the new bonds to form.
◉ Characteristics of Equilibrium
Answer: 1. In a closed system - no matter enters or leaves the
system
2. Macroscopic Properties (State, colour, temperature and
pressure) stay constant
3. Concentration of reactants and products stay constant (NOT
equal)
4. Rate of forward reaction = Rate of backward reaction
◉ Differences between Static and Dynamic Equilibrium
,Answer: Static Equilibrium:
- Forward + Reverse Reaction at the same rate
- Concentrations remain constant
- Reaction has reached completion
-→
- Reactions + Product do not interact
- Non-Reversible Reaction
Dynamic Equilibrium
- Forward + reverse reactions at the same rate
- Concentration remains constant
- Reaction never reaches completion
-⇌
- Reactions + Products interact
- Reversible Reactions
◉ How to notice Dynamic Equilibrium in a graph
Answer: You can notice dynamic equilibrium when the
concentrations of both reactants and products stay constant but
dynamic.
◉ What is an example of Static Equilibrium
, Answer: For Example: C-Diamond and graphite. At room
temperature, you are not going to see either reaction taking place,
so this could be considered a static equilibrium situation.
◉ What was the aim for the: reversible and irreversible reaction
Answer: To observe the several chemical reactions and determine
whether they are reversible or not
◉ Method for the: Reversible and Irreversible Reaction
Answer: 1. Cobalt(II) Chloride Hydrated and Dehydrated
CoCl2 + 6H2O ⇌ CoCl2.6H2O
2. Iron(III) Nitrate and Potassium Thiocyanate
Fe+3(aq) + SCN(aq) ⇌ FeSCN+2(aq)
- When you increase concentration of Fe in FeSCN it suggest a
forward reaction and the darker red shows this
- When you increase concentration of SCN, in FeSCN it suggests a
forward reaction as the solution gets darker red showing that
more reactant are being used up in products
- Decrease in colour suggest decrease in colour
- The adding of Ag allows for precipitation to be formed with SCN,
therefore removing itself from FeSCN solution, showing a reverse
reaction hence the murky white
3. Burning Magnesium
2Mg + O2 → 2MgO
4. Burning Steel Wool
