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Chemistry > Static and Dynamic Equilibrium > Flashcards

Static and Dynamic Equilibrium Flashcards

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1
Q

Closed system

A

a system that only exchanges energy with its surroundings, but not matter.

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2
Q

4 reasons that show a chemical system has reached equilibrium:

A
  1. It is a closed system - no matter enters or leaves the system
  2. Macroscopic properties (e.g. state, colour, temperature and pressure) stay constant
  3. Concentrations of reactant and products stay constant
  4. Rate of forward reaction = rate of reverse reaction
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3
Q

Homo, hetero

A

Homo - same state

Hetero - different states

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4
Q

Dynamic equilibrium

A
  1. Reactants are converted to products and products are converted to reactants at an equal and constant rate.
  2. Concentration does not change but is dynamic
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5
Q

Static equilibrium

A

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. It is also irreversible. Example: two allotropes of carbon - diamond and graphite converting

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6
Q

Collision theory

A

Need to collide once they reach activation energy to break the bonds and have to face the same direction to allow new bonds to form.

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7
Q

Equilibrium reactions with collision theory (hint: forward & reverse reaction)

A
  1. the reactants collide with each other and form products in the forward reaction.
  2. product molecules collide and decompose to reform reactants in the reverse reaction.
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8
Q

Summarise collision theory and equilibrium together

A
  1. Concentration of reactant molecules decreases and so does the frequency of collisions, this means there is less product being produced as well.
  2. Once forward and reverse reactions reach the same rate. Products form at exactly the same rate as they are decomposing. ∴ The concentrations of reactants and products remain constant.
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9
Q

How can collision theory and activation energy be reversible?

A

For a reaction to be reversible, the activation energies of both the forward and reverse reactions must be low enough that sufficient particles will have enough energy for a successful collision.

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10
Q

What is a non-equilibrium system?

A

Irreversible and can never reach equilibrium

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11
Q

What are the 2 non-equilibrium systems?

A

➜ Combustion reactions

➜ Photosynthesis

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12
Q

What is the enthalpy for combustion?

A

Negative because it is an exothermic reaction

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13
Q

What is the enthalpy, entropy, and Gibbs free energy for Photosynthesis?

A

Enthalpy ∆H

  • Positive
  • Endothermic reaction

Entropy ∆S

  • Negative
  • Decrease in particles

Gibbs Free Energy ∆G

  • Positive
  • Non-spontaneous
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14
Q

The 4 Le Chatelier’s Principle changes are:

A
  • Concentration
  • Pressure, Volume
  • Temperature
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15
Q

2, Effect of concentration on equilibrium

A

If concentration of a reactant or product is increased, the equilibrium will shift to the other side to use up the added chemical.

If concentration of a reactant or product is decreased, the equilibrium shifts to replace the substance removed.

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16
Q

Does adding more of a solid have an effect on equilibrium?

A

No

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17
Q

2, Effect of Pressure and Volume Changes on Equilibrium

A

If pressure is increased, volume decreases. This will be towards the side with fewer gaseous particles. Because there are fewer collisions.

If pressure is decreased, volume increases. This will be towards the side with more gaseous particles. Because there are more collisions.

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18
Q

2, Effect of Temperature Changes on Equilibrium

A

If temperature of an equilibrium system increases the equilibrium position moves in whichever direction absorbs heat

If temperature of an equilibrium system is decreased, the system will move in whichever direction produces more heat.

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19
Q

2, Effect of a Catalyst on Equilibrium

A

Adding a catalyst will provide an alternative pathway of lower activation energy - this will allow both the forward and reverse reactions to occur at a faster rate

No visible effect

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20
Q

Changes in Temperature - Equilibrium Graph

A

It is going to gradually affect both reactants and products

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21
Q

Changes in Concentration - Equilibrium Graph

A

After the equilibrium is disturbed the change will show a sharp spike - ONLY one spike

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22
Q

Changes in Pressure - Equilibrium Graph

A

There will be a sharp spike for BOTH reactants and products

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23
Q

Equilibrium Constant Formula, 2

A

aA + bB → cC + dD

Products over Reactants

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24
Q

What is equilibrium constant affected by?

A

When temperature increases and decreases, the K value: copies/favours Le Chatelier’s Principle

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25
Q

Size of the Equilibrium Constant

A

If K is:
Large = favours Products (high concentration, compared to reactants)
Small = favours Reactants (High concentration, compared to products)
0.001 to 1000 = Significant amount of both reactant and products

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26
Q

ICE Table, 3

A
  1. Initial Concentration (mol L-1)
  2. Change in Concentration (based on mole ratio) (mol L-1)
  3. Equilibrium Concentration (mol L-1)
27
Q

Type 3: Constant Calculations (%)

A

When given the percentage of decomposition, calculate how much this represents as a concentration and place this in the table under change in concentration

28
Q

Type 4: Constant Calculations

A

Whenever you see horizontal lines – means equilibrium, plug in numbers and calculate K. Be careful sometimes the concentration may not be in mol L-1

29
Q

Dissociation Reaction

A

A Dissociation Reaction is one in which a compound breaks up into one or two parts.

30
Q

Dissociation of Ionic Solutions

A

The separation of Ions that occurs when a Solid Ionic compound Dissolves.

31
Q

Dissociation of Acids

A

Acids form Hydrogen ions (H+) in an aqueous solution

Weak Acids = ⇌ (reversible)
Strong Acids = → (one direction)

If KA value is a big number then it is a strong acid

When the KA is exothermic, KA decreases with increasing temperature. VICE VERSA. (Le Chatellier)

32
Q

Dissociation of Bases

A

Dissociates in water to form an Equilibrium mixture, they have the constant KB

A small number indicates it’s a weak base

33
Q

Keq of a Chemical Equilibrium System - Colorimeters

A

Measures the percentage of a given wavelength of light

The higher the amount of light absorbed, the more concentrated. Vice Versa

Higher transmission means it is lighter, less concentrated.

34
Q

How to Calculate reactants?

A

(Initial Reactant Concentration) - (Equilibrium concentration)

[Fe3+] = [Fe3+] initial – (c)
[SCN-] = [SCN-] initial – (c)
35
Q

Ion-dipole attraction

A

Most ionic compounds dissolve in water because polar water molecules have a strong attraction for charged ions

(Ion and polar molecule)

36
Q

What do ionic substances that dissolve in the water turn into?

A

ions ( their basic form)

37
Q

Electricity conduction ions

A

Ionic compounds conduct electricity when in an aqueous solution → as ions move through the solution when an electric current flows through it.

38
Q

Solubility in water

A

Substances which can form strong bonds with water molecules tend to be very soluble in water.

If it is insoluble Ion-ion interactions in the solid are much stronger than the ion-water interactions

39
Q

What must be broken first for ions to dissolve in water

A

Interaction between water molecules –> hydrogen bonding must be broken for ions to dissolve in water.

Electrostatic attraction interactions between the ions of an ionic compound, forming their ionic bonds. These bonds also need to be broken for ions to dissolve in water.

40
Q

What charged ions will be attracted to what?

A

Cations will be attracted to the partially negatively charged oxygen
Anions will be attracted to the partially positively hydrogen ions

41
Q

The toxin in plants

A

Cycasin found in Cycad plant

42
Q

How is the toxin removed?

A

Removed by leaching, which involves the use of water to dissolve the toxin and remove it from the plant.

43
Q

What way will the equilibrium move in a constant moving water source?

A

By having a constantly moving/changing water source, the equilibrium will always be shifting to the right. The longer you wait, the less toxic the fruit will be

44
Q

Precipitate

A

When two ionic compounds mix together, an insoluble solid called a precipitate is produced.

Occurs because not all ionic compounds are soluble.

The ions are more strongly attracted to each other than to water.

Remember to Write net ionic equations

45
Q

Go study Solubility Rules

A

Okay

46
Q

Solubility and Equilibrium

A

A saturated solution is in a state of dynamic equilibrium between the dissolved, dissociated, ionic compound and the undissolved solid

47
Q

KSp

A

The Smaller the Ksp, the more insoluble and less dissociation

The Larger the Ksp, the more soluble and more dissociation

48
Q

Calculation 1: Given concentration of ions present in the solution at equilibrium

A

Write the chemical equation for the substance dissolving and dissociating.
Write the Ksp expression.
Substitute the concentration of each ion into the equilibrium expression and calculate Ksp.

49
Q

Calculation 2: Given molar solubility of the ionic compound

A

Same thing as calculation 1, except determine the concentration of each ion using mole ratios from the balanced equation.

50
Q

Calculation 3: Calculating Molar Solubility from Ksp

A

Same thing as 1 except put reactants as x and then solve, make sure to include mole ratio

51
Q

Predicting the Formation of a Precipitate - Ksp & Ionic Product

A

Solubility Product is only for saturated solutions

Ionic Product (Q) is for all types of solutions - it is the product of the concentrations of the ions in a solution

52
Q

Predicting Whether Precipitation Will Occur – Given Ion Concentrations - Steps

A

1) Calculate the concentration of individual ions in the combined solution.
2) Calculate the ionic product, Q.
3) Compare Q to Ksp.

No need for molar ratio

53
Q

Compare Q to Ksp results

A

Q < Ksp
Unsaturated
No precipitation

Q = Ksp
Saturated
Solution at equilibrium precipitation

Q > Ksp
Supersaturated
Precipitation

54
Q

Saturated Solution

A

A solution that contains the maximum amount of solute that is capable of being dissolved.

55
Q

Common Ion Effect

A

Ionic salt is present in solution, and then another chemical is added, which has an ion in common with the original ionic salt. The solubility of the ionic salt will decrease.

56
Q

What is the purpose of an indicator?

A

A substance can be classified as acidic, basic, or neutral according to the change in colour found in indicators.

57
Q

Acid and Base Formula

A

Acid + Base → Salt + Water

Proton Transfer to form water

58
Q

Acid and Carbonate Formulas

A

Acid + Carbonate → Salt + Water + Carbon Dioxide

Acid + Hydrogen carbonate → Salt + Water + carbon dioxide

59
Q

Acid and Metal Formula

A

Metal + Acid (dilute) → Salt + Hydrogen

Nitric acid and concentrated sulfuric acid do not react in this way metals

60
Q

Base Definition

A

A base is a substance that can react with acids and neutralise them. Bases are usually:

  • metal oxides, such as copper oxide
  • metal hydroxides, such as sodium hydroxide, or
  • metal carbonates, such as calcium carbonate
61
Q

Applications of Neutralisation Reactions

A

Antacids are substances such as sodium bicarbonate (NaHCO3). They are used to neutralise the stomach acid
(HCl).

62
Q

Bronsted-Lowry - proton acceptor and donator

A
  • An acid is a proton donor
  • A base is a proton acceptor
  • An acid-base reaction is a proton transfer; such reaction involves two acid-base pairs
63
Q

Conjugates

A
  • An acid gives up a proton to form what is called the conjugate base
  • A base accepts a proton to form what is called the conjugate acid
64
Q

Limitation of Bronsted-Lowry

A

Brønsted-Lowry theory cannot explain the reactions between acidic oxides and basic Oxides

Chemistry (2 decks)

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