Module 8 Textbook Questions

True or False; Matter is neither created nor destroyed in a chemical reaction. (a) True (b) False

(a) True

SKILLBUILDER 8.1 | Evidence of a chemical reaction. Which changes involve a chemical reaction? Explain you answers. (a) butane burning in a butane lighter. (b) butane evaporating out of a butane lighter (c) wood burning (d) dry ice subliming

(a) chemical reaction; heat and light are emitted. (b) not a chemical reaction; gaseous and liquid butane are both butane. (c) chemical reaction; heat and light are emitted. (d) not a chemical reaction; solid dry ice is made of carbon dioxide, which sublimes (evaporates) as carbon dioxide gas.

List the abbreviation that indicate the states of reactants and products in chemical equations. (a) gas (b) liquid (c) solid (d) aqueous (indicates a substance is dissolved in water, called an aqueous solution)

(a) gas - (g) (b) liquid - (l) (c) solid - (s) (d) aqueous - (aq)

Which changes involve a chemical reaction? Explain you answers. (a) ice melting upon warming. (b) an electric current passing through water, resulting in the formation of hydrogen and oxygen gas that appears as bubbles rising. (c) iron rusting. (d) bubbles form when a soda can is opened.

(a) not a chemical reaction; melting ice forms water, but both the ice and water are composed of water molecules. (b) chemical reaction; water decomposes into hydrogen and oxygen, as evidenced by the bubbling. (c) chemical reaction; iron changes into iron oxide, changing colour in the process. (d) not a chemical reaction; even though there is bubbling, it is just carbon dioxide coming out of the liquid.

Which quantity must always be the same on both sides of a balanced chemical equation? (a) the number of each type of atom (b) the number of each type of molecule (c) the sum of all coefficients

(a) the number of each type of atom The number of each type of atom must be the same on both sides of a balanced chemical equation. Since molecules change during a chemical reaction, their number is not the came on both sides (b), nor is the sum of all coefficients the same (c).

True or False: Consider a drop of water that is put into a flask, sealed with a cap, and heated until the droplet vaporizes. The mass of the container and water will be different after heating? (a) True (b) False

(b) False The mass will be the same as before it was heated, the only change will be the state of the water (H₂O). The water will have undergone a physical change from a liquid state (l) to a gaseous state (g).

SKILLBUILDER 8.5 | Write a balanced equation for the reaction of aqueous lead (II) acetate with aqueous potassium iodide to form solid lead (II) iodide and aqueous potassium acetate.

Balanced equation: Pb(C₂H₃O₂)₂(aq) + 2 KI(aq) → PbI₂(s) + 2 KC₂H₃O₂(aq)

SKILLBUILDER 8.6 | Balance the chemical equation. HCI (g) + O₂ (g) → H₂O (l) + Cl₂ (g)

Balanced equation; 4 HCI (g) + O₂ (g) → 2 H₂O (l) + 2 Cl₂ (g)

Which are the reactants an which are the products in the chemical equation below? CH₄(g) + O₂(g) → CO₂(g) + H₂O(g)

CH₄(g) + O₂(g) → CO₂(g) + H₂O(g) reactants products ● the substances displayed on the left side are the reactants, the substances displayed on the right side are the products.

What is the balanced chemical equation for the following? Balance by inserting correct coefficients. In photosynthesis, plants make the sugar glucose, C₆H₁₂O₆, from Carbon dioxide (CO₂) and Water (H₂O). The equation for the reaction is: CO₂ + H₂O → C₆H₁₂O₆ + CO₂

The balanced chemical equation for CO₂ + H₂O → C₆H₁₂O₆ + CO₂ is as follows; 6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 CO₂

SKILLBUILDER 8.2 | Conservation of Mass Suppose 12 g of natural gas combines with 48 g of oxygen in a flame. The chemical change produces 33 g of carbon dioxide. How many grams of water form?

The sum of the masses of the natural gas and water is: 12 g + 48 g = 60 g The sum of the masses of carbon dioxide and water must also equal 60 grams in total (law of conservation of masses) thus, 27g of water would form. 33g of CO₂ + 27g of H₂O = 60 g

A chemist forms 16.6 g of potassium iodide by combining 3.9 g of potassium with 12.7 g of iodine. Show that these results are consistent with the law of conservation of mass.

The sum of the masses of the potassium and iodine is: 3.9 g + 12.7 g = 16.6 g The sum of the masses of potassium and iodine equals the mass of the product, potassium iodide. The results are consistent with the law of conservation of mass.

SKILLBUILDER 8.3 | Write a balanced equation for the reaction between solid Chromium (III) oxide and solid Carbon to produce solid Chromium and Carbon Dioxide gas.

Unbalanced: Cr₂O₃ (s) + C (s) → Cr (s) + CO₂ (g) reactants products 2 Cr atoms → 1 Cr atom 3 O atoms → 2 O atoms 1 C atom → 1 C atom Balanced: 2 Cr₂O₃ (s) + 3 C (s) → 4 Cr (s) + 3 CO₂ (g) reactants products 4 Cr atoms → 4 Cr atom 6 O atoms → 6 O atoms 3 C atom → 3 C atom

SKILLBUILDER 8.4 | Write a balanced equation for the combustion reaction of gaseous C₄H₁₀ (butane) and gaseous oxygen to form gaseous carbon dioxide and gaseous water.

Unbalanced: C₄H₁₀ (g) + O₂ (g) → CO₂ (g) + H₂O (g) reactants products 4 C atoms → 1 C atom 10 H atoms → 2 H atoms 2 O atom → 2 O atom Balanced: 2 C₄H₁₀ (g) + 13 O₂ (g) → 8 CO₂ (g) + 10 H₂O (g) reactants products 8 C atoms → 8 C atom 10 H atoms → 10 H atoms 26 O atom → 26 O atom

What is the unbalanced, and balanced chemical equation for a natural-gas flame of Methane (CH₄) reacting with Oxygen (O₂) to form Carbon Dioxide (CO₂) and Water (H₂O)?

Unbalanced: CH₄(g) + O₂(g) → CO₂(g) + H₂O(g) Balanced: CH₄(g) + 2 O₂(g) → CO₂(g) + 2 H₂O(g)