Chapter 3

Question 1

What does a chemical equation show?

Answer 1

The reactants, products, and their relative amounts in a reaction.

Question 2

What are stoichiometric coefficients?

Answer 2

The numbers in front of chemical formulas that indicate the ratio of reactants and products.

Question 3

What does the Law of Conservation of Matter state?

Answer 3

Matter cannot be created or destroyed in a chemical reaction; total atoms are conserved.

Question 4

what should be the same according to law of conservation of mass and chemical equations.

Answer 4

of atoms need to be balanced on both sides of the equation

Question 5

What can you change when balancing chemical equations?

Answer 5

Only the coefficients, not the subscripts.

Question 6

What are the steps for balancing an equation?

Answer 6

Write formulas with correct states

Balance the most complex compound first

Balance free elements last

Check atom count

Simplify if needed

Question 7

What does ⇌ represent in a chemical equation?

Answer 7

A reversible reaction at equilibrium.

Question 8

What happens at chemical equilibrium?

Answer 8

Forward and reverse reactions occur at the same rate; concentrations remain constant.

Question 9

What is an electrolyte?

Answer 9

A substance that produces ions and conducts electricity in water.

Question 10

What’s the difference between strong, weak, and nonelectrolytes?

Answer 10

Strong: 100% ionized

Weak: partially ionized

Nonelectrolyte: no ions

Question 11

Is NaCl a strong, weak, or nonelectrolyte?

Answer 11

Strong electrolyte

Question 12

Is sugar (C₁₂H₂₂O₁₁) a strong, weak, or nonelectrolyte?

Answer 12

Nonelectrolyte

Question 13

What is a precipitation reaction?

Answer 13

A reaction where an insoluble solid (precipitate) forms from two aqueous solutions.

Question 14

What are spectator ions?

Answer 14

Ions that do not participate in the actual chemical change.

Question 15

What is a net ionic equation?

Answer 15

An equation showing only the ions and molecules involved in the reaction, with spectator ions removed.

Question 16

What is the net ionic equation for Pb(NO₃)₂ + KI → ?

Answer 16

Pb²⁺(aq) + 2I⁻(aq) → PbI₂(s)

Question 17

Arrhenius acid and base definitions?

Answer 17

Acid: Increases H⁺ in water
Base: Increases OH⁻ in water

Question 18

Brønsted–Lowry acid and base definitions?

Answer 18

Acid: Proton donor
Base: Proton acceptor

Question 19

What is a strong acid?

Answer 19

One that completely ionizes in water.

Question 20

Example of a polyprotic acid?

Answer 20

H₂SO₄ (diprotic), H₃PO₄ (triprotic)

Question 21

What is the net ionic equation for strong acid + strong base?

Answer 21

H⁺(aq) + OH⁻(aq) → H₂O(l)

Question 22

What gas forms when metal carbonates react with acids?

Answer 22

CO₂(g)

Question 23

What is the overall reaction of CaCO₃ + HCl?

Answer 23

CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l)

Question 24

Which anions form gases with acids?

Answer 24

CO₃²⁻, HCO₃⁻, S²⁻

Question 25

Which cation forms a gas with base?

Answer 25

NH₄⁺ forms NH₃(g)

Question 26

What is oxidation?

Answer 26

Loss of electrons

Question 27

What is reduction?

Answer 27

Gain of electrons

Question 28

What is the oxidizing agent?

Answer 28

The substance that is reduced (gains electrons)

Question 29

Oxidation number of O in H₂O?

Answer 29

-2

Question 30

Oxidation number of H in NaH?

Answer 30

-1 (hydride)

Question 32

Redox reaction example:

Answer 32

Fe₂O₃ + 2Al → 2Fe + Al₂O₃

Question 33

What are the four main types of aqueous reactions?

Answer 33

Precipitation Acid–Base Gas-forming Redox

Question 34

What are signs a chemical reaction has occurred?

Answer 34

Gas evolution, color change, precipitate formation, temperature change

Question 35

What is a combination reaction?

Answer 35

A + B → AB

Question 36

What is a decomposition reaction?

Answer 36

AB → A + B