5.1

Question 1

In what type of system does equilibrium occur?

Answer 1

Equilibrium occurs in a closed system, meaning that matter cannot enter or leave the system

Question 2

What is Solubility Equilibrium?

Answer 2

Solubility Equilibrium is reached when the rate of dissolving equals the rate of crystallization

Question 3

What must be present at Solubility Equilibrium?

Answer 3

Both dissolved and undissolved solute must be present at the same time

Question 4

Fill in the blank: At Solubility Equilibrium, the concentration of the dissolved solute is _______.

Answer 4

constant

Question 5

True or False: The concentrations of reactants and products vary constantly in a dynamic equilibrium.

Answer 5

False

Question 6

What occurs at equal rates in a chemical equilibrium?

Answer 6

The forward and reverse reactions occur at equal rates

Question 7

What is a closed system in the context of equilibria?

Answer 7

A system where no matter enters or leaves, allowing for equilibrium to be established.

Question 8

What type of equilibrium is established at the melting/freezing point?

Answer 8

Solid/liquid equilibrium

Question 9

At 0°C, what is the relationship between the rate of melting and the rate of freezing?

Answer 9

The rate of melting equals the rate of freezing.

Question 10

What is the characteristic of gas pressure at equilibrium in a closed system?

Answer 10

The pressure of gas remains constant.

Question 11

What defines quantitative reactions in an open system?

Answer 11

A chemical reaction that proceeds to completion, preventing reverse reactions.

Question 12

How does equilibrium differ in a closed system compared to an open system?

Answer 12

In a closed system, an equilibrium can be reached, whereas in an open system, molecules can leave, preventing equilibrium.

Question 13

What is an example of a reversible reaction?

Answer 13

The reaction between nitrogen dioxide (NO2) and nitric oxide (NO) at equilibrium.

Question 14

What does it mean for an equilibrium to have the same composition regardless of approach?

Answer 14

It means the equilibrium will have the same composition whether approached from reactants or pure products.

Question 15

What are the two ways to describe the state of chemical equilibrium?

Answer 15

a) Percentage reaction
b) Equilibrium constant

Question 16

How is the equilibrium constant (K) defined for the reaction aA + bB ⇌ cC + dD?

Answer 16

K = |C|^c |D|^d / |A|^a |B|^b

Question 17

Fill in the blank: At chemical equilibrium, the yield of product is measured as a percentage of the _______.

Answer 17

[maximum possible yield of product]

Question 18

True or False: Chemical equilibrium can only occur in closed systems.

Answer 18

False

Question 19

What is the significance of ‘58 kJ/mol’ in the context of chemical reactions?

Answer 19

It represents the heat involved in the reaction, indicating energy changes.

Question 20

What is the formula for calculating percent reaction?

Answer 20

Percent reaction = (actual product yield / theoretical product yield) × 100%

The theoretical product yield is obtained from mole ratio and stoichiometric calculations.

Question 21

What are the initial concentrations of hydrogen and iodine in experiment 1?

Answer 21

• H2(g): 1.00 mmol/L
• I2(g): 0.50 mmol/L

These concentrations are recorded before any reaction occurs.

Question 22

What does ‘No reaction (NR)’ indicate in terms of reaction favorability?

Answer 22

Reactants favored

This indicates that the reaction does not proceed significantly towards products.

Question 23

What percentage reaction indicates that reactants are favored?

Answer 23

< 50%

This suggests that the equilibrium position lies closer to the reactants than products.

Question 24

What percentage reaction indicates that products are favored?

Answer 24

> 50%

This suggests that the equilibrium position lies closer to the products than reactants.

Question 25

What is the equilibrium concentration of H2(g) at 448 °C after the reaction?

Answer 25

0.100 mmol/L

This is the concentration of hydrogen at equilibrium.

Question 26

What is the equilibrium concentration of HI(g) at 448 °C?

Answer 26

2.00 mmol/L

This concentration represents the product formed at equilibrium.

Question 27

In the context of chemical reactions, what does ‘quantitative’ mean?

Answer 27

Reaction proceeds to completion

This implies that all reactants are converted into products.

Question 28

What is the average product yield if the actual yield is 1.56 mmol/L and the theoretical yield is 2.00 mmol/L?

Answer 28

78.0%

This is calculated using the percent reaction formula.

Question 29

What is the significance of stoichiometric calculations in reversible reactions?

Answer 29

Used to calculate the concentrations of reactants and products at equilibrium

Stoichiometric calculations help predict the amounts of substances involved in a reaction.

Question 30

Fill in the blank: The actual product yield is calculated from the equilibrium concentrations and is compared to the _______.

Answer 30

theoretical product yield

This comparison is essential for determining the efficiency of the reaction.

Question 31

True or False: A reaction with a percent yield of > 99% indicates a complete conversion of reactants to products.

Answer 31

True

This indicates that the reaction has gone nearly to completion.