Mod 14

Question 1

What is collision theory?

Answer 1

Reactions occur when particles collide with sufficient energy and correct orientation.

Question 2

Define activation energy (Ea).

Answer 2

The minimum energy barrier particles must overcome.

Question 3

How is the rate of a reaction measured?

Answer 3

As change in concentration per unit time.

Question 4

What effect does higher temperature have on reaction rates?

Answer 4

Higher temperature → higher kinetic energy → faster reaction.

Question 5

What happens to collision frequency when reactant concentration increases?

Answer 5

Greater reactant concentration increases collision frequency.

Question 6

What is the role of catalysts in chemical reactions?

Answer 6

Catalysts lower Ea, speeding both forward and reverse reactions without being consumed.

Question 7

What happens to the rate of the reaction 2 CO(g) + O₂(g) → 2 CO₂(g) when temperature is lowered?

Answer 7

Rate decreases.

Question 8

How does adding a catalyst affect activation energy?

Answer 8

Provides an alternate pathway with lower Ea.

Question 9

What occurs at chemical equilibrium?

Answer 9

Forward and reverse reaction rates are equal.

Question 10

How do concentrations behave at equilibrium?

Answer 10

Concentrations become constant but rarely equal.

Question 11

What symbol denotes a reversible reaction?

Answer 11

Double arrow (⇌).

Question 12

What is Kc in chemical equilibrium?

Answer 12

Kc relates product and reactant concentrations at equilibrium.

Question 13

What does a large Kc value (>10²) indicate?

Answer 13

Product-favored.

Question 14

What does a small Kc value (<10⁻²) indicate?

Answer 14

Reactant-favored.

Question 15

What is omitted from Kc expressions?

Answer 15

Pure solids and liquids.

Question 16

How do units of Kc depend?

Answer 16

Units depend on stoichiometry.

Question 17

Write the Kc expression for the reaction N₂ + 3 Cl₂ ⇌ 2 NCl₃.

Answer 17

Kc=[NCl₃]²/([N₂][Cl₂]³).

Question 18

What does Kc predict?

Answer 18

Composition; unknown concentrations solved algebraically.

Question 19

What does Le Châtelier’s principle state?

Answer 19

A system shifts to relieve applied stress (concentration, pressure/volume, temperature).

Question 20

Define Arrhenius acids.

Answer 20

Produce H⁺ in water.

Question 21

Define Arrhenius bases.

Answer 21

Produce OH⁻ in water.

Question 22

What is the Brønsted-Lowry definition of acids and bases?

Answer 22

Acids donate H⁺, bases accept H⁺.

Question 23

What color does litmus turn in the presence of acids?

Answer 23

Red.

Question 24

What color does litmus turn in the presence of bases?

Answer 24

Blue.

Question 25

What is a conjugate acid-base pair?

Answer 25

Differ by one proton.

Question 26

Name the conjugate base of H₂S.

Answer 26

HS⁻.

Question 27

Name the conjugate acid of NO₂⁻.

Answer 27

HNO₂.

Question 28

How do strong acids behave in terms of dissociation?

Answer 28

Dissociate ~100%.

Question 29

How do weak acids behave in terms of dissociation?

Answer 29

Only partially dissociate.

Question 30

What does Ka quantify?

Answer 30

Acid strength; larger Ka = stronger acid.

Question 31

List the common strong acids.

Answer 31

* HCl * HBr * HI * HNO₃ * H₂SO₄ * HClO₄

Question 32

List examples of strong bases.

Answer 32

* Group 1 & 2 metal hydroxides (e.g., NaOH, Ca(OH)₂)

Question 33

What is the auto-ionization reaction of water?

Answer 33

2 H₂O ⇌ H₃O⁺ + OH⁻.

Question 34

What is the value of Kw at 25 °C?

Answer 34

1.0×10⁻¹⁴.

Question 35

What indicates an acidic solution in terms of [H₃O⁺] and [OH⁻]?

Answer 35

[H₃O⁺] > [OH⁻].

Question 36

What indicates a neutral solution in terms of [H₃O⁺] and [OH⁻]?

Answer 36

Equal concentrations.

Question 37

What indicates a basic solution in terms of [H₃O⁺] and [OH⁻]?

Answer 37

[H₃O⁺] < [OH⁻].

Question 38

What is the formula for calculating pH?

Answer 38

pH = –log[H₃O⁺].

Question 39

What is the pH scale range?

Answer 39

0-14.

Question 40

How do you find the pH of a solution with [H₃O⁺] = 6.38×10⁻⁴ M?

Answer 40

pH = 3.195.

Question 41

What happens when acids react with metals?

Answer 41

Produce H₂ gas.

Question 42

What happens when acids react with carbonates?

Answer 42

Produce CO₂ gas.

Question 43

What is the result of neutralization reactions?

Answer 43

Acid + base → salt + water.

Question 44

What is the basis of titrations?

Answer 44

Neutralization reactions.

Question 45

Calculate the molarity of HCl if 18.5 mL 0.225 M NaOH neutralizes 10.0 mL HCl.

Answer 45

M(HCl) = 0.416 M.

Question 46

How many mL of 2.00 M H₂SO₄ are required to neutralize 50.0 mL 1.00 M KOH?

Answer 46

12.5 mL.

Question 47

What is a buffer?

Answer 47

Contains weak acid/base pair that resists pH changes.

Question 48

How do buffers respond to added H⁺?

Answer 48

Neutralized by base.

Question 49

How do buffers respond to added OH⁻?

Answer 49

Neutralized by acid.

Question 50

Calculate the pH of a buffer solution with 0.20 M H₂CO₃ and 0.10 M HCO₃⁻ (Ka=4.3×10⁻⁷).

Answer 50

pH ≈ 6.07.

Question 51

What is the pH of 0.010 M HNO₃?

Answer 51

2.00.

Question 52

Name the acids in water.

Answer 52

* HClO₄ * HI

Question 53

Fill in the conjugate base of HClO₃.

Answer 53

ClO₃⁻.

Question 54

Fill in the conjugate acid of HSO₄⁻.

Answer 54

H₂SO₄.