Practice Questions

When aqueous solutions of lead(II) nitrate ($Pb(NO_3)_2$) and potassium iodide ($KI$) are mixed, a yellow precipitate of lead(II) iodide ($PbI_2$) is formed along with aqueous potassium nitrate ($KNO_3$). Create a balanced chemical equation for this double displacement reaction, including the correct state symbols for all substances involved.

Justify the necessity of balancing a chemical equation using a fundamental law of chemistry.

Create a general word equation to represent any single displacement reaction involving a metal 'A', and a salt solution of another metal 'B', where 'A' is more reactive than 'B'.

Identify the reactants and products in the following reaction: $Zn(s) + H_2SO_4(aq) \rightarrow ZnSO_4(aq) + H_2(g)$.

What is a skeletal chemical equation? Provide an example.

The shiny finish on freshly whitewashed walls is due to the formation of calcium carbonate. This happens when slaked lime (calcium hydroxide, $Ca(OH)_2$) reacts with a gas present in the air. Formulate the balanced chemical equation for this reaction, including state symbols, and identify the type of reaction.

Apply your knowledge of oxidation to explain why manufacturers of potato chips flush the bags with nitrogen gas.

Define a chemical reaction.

Name the type of reaction represented by the equation: $Na_2SO_4(aq) + BaCl_2(aq) \rightarrow BaSO_4(s) + 2NaCl(aq)$. Also, identify the precipitate formed.

Propose a single term that accurately describes a reaction where an insoluble solid is formed from two aqueous solutions.

Apply the definition of oxidation to determine if magnesium is oxidized or reduced in the reaction where it burns in air to form magnesium oxide ($2Mg + O_2 \rightarrow 2MgO$).

Apply the appropriate physical state symbols (s, l, g, aq) to the reactants and products in the balanced chemical equation for the reaction of sodium metal with water to form sodium hydroxide solution and hydrogen gas.

Explain why chemical equations must be balanced.

Define a combination reaction and provide an example with a balanced chemical equation.

What is a decomposition reaction? Explain why it is called the opposite of a combination reaction.

Summarize the process of corrosion. Name the chemical process responsible for it and give two common examples.

Compare and contrast combination reactions and decomposition reactions. Provide one example for each type of reaction, including a balanced chemical equation.

To balance the equation for the combustion of methane ($CH_4 + O_2 \rightarrow CO_2 + H_2O$), a student changes the formula of water to $H_4O_2$ to balance the hydrogen atoms. Critique this method. Is it a valid approach? Justify your reasoning based on the fundamental rules of writing chemical formulas and balancing equations.

Describe what happens when calcium oxide (quick lime) is added to water. Name the type of reaction and write the chemical equation.

Demonstrate the step-by-step process of balancing the chemical equation for the reaction of iron with steam to form iron(II,III) oxide and hydrogen gas: $Fe + H_2O \rightarrow Fe_3O_4 + H_2$

Examine the process of respiration and explain why it is considered an exothermic reaction.

A student adds a small amount of calcium oxide (quicklime) to water in a beaker. Apply your knowledge of chemical reactions to predict two observable changes and write the balanced equation for the reaction.

You observe that when a strip of metal 'M' is placed in a blue solution of copper(II) sulfate ($CuSO_4$), the blue color fades and a reddish-brown deposit forms on the metal strip. When a strip of silver (Ag) is placed in a similar solution, no change is observed. Formulate a hypothesis about the relative reactivity of metals M, Cu, and Ag, and justify your reasoning based on the principles of displacement reactions.

In the electrolysis of acidified water (Activity 1.7), two gases are collected in separate test tubes. The volume of gas collected at the cathode is double the volume of gas collected at the anode. a) Formulate the balanced chemical equation for this decomposition reaction. b) Justify why the volume of one gas is double that of the other, referencing the stoichiometry of your balanced equation. c) Propose a simple chemical test to identify the gas collected at the cathode and describe the expected observation.

Define a displacement reaction. Use the reaction between an iron nail and copper sulphate solution to explain the concept.

Explain the term 'rancidity' and list two methods to prevent it.

Analyze the following skeletal chemical equation for the formation of ammonia from nitrogen and hydrogen. Solve the equation by balancing it and identify the type of chemical reaction it represents. $N_2(g) + H_2(g) \rightarrow NH_3(g)$

Analyze what happens when a piece of zinc metal is placed in a blue solution of copper(II) sulphate. Explain the observations in terms of reactivity and write the balanced chemical equation for the reaction.

List four observations that help determine if a chemical reaction has taken place.

When an aqueous solution of lead(II) nitrate is mixed with an aqueous solution of potassium iodide, a yellow precipitate is formed. Analyze this reaction to identify the yellow precipitate, name the type of reaction, and write a balanced chemical equation.

Respiration is described by the equation: $C_6H_{12}O_6(aq) + 6O_2(aq) \rightarrow 6CO_2(aq) + 6H_2O(l) + \text{energy}$. Justify why this process can be classified as both an exothermic reaction and a redox reaction. Identify the substance being oxidized and the substance being reduced.

A student writes the following equation for the reaction of iron with steam: $3Fe(s) + 4H_2O(l) \rightarrow Fe_3O_4(s) + 4H_2(g)$. Critique this equation. Is it completely correct? Justify your evaluation by identifying any potential errors and proposing the necessary corrections.

Design a simple home experiment to investigate the factors that cause rancidity in potato chips. Your design must include: a) A clear hypothesis. b) A list of materials needed (using common household items). c) The procedure, including a control group and at least two experimental variables. d) The observations you would expect to make to support or refute your hypothesis.

Corrosion of iron is a significant problem. Propose two distinct methods to prevent the rusting of an iron gate. For each method, create a brief explanation justifying how it prevents the underlying oxidation-reduction reaction responsible for rust formation.

After heating a white crystalline solid and observing the emission of a gas, a student concludes it must be a thermal decomposition reaction. Critique this conclusion. Is it definitively correct?

Examine the following decomposition reactions. For each reaction, identify the form of energy (heat, light, or electricity) responsible for the decomposition and write the balanced chemical equation. (a) Decomposition of calcium carbonate into quicklime and carbon dioxide. (b) Decomposition of water into hydrogen and oxygen gas. (c) Decomposition of silver chloride into silver and chlorine.

A classmate claims, "All combination reactions are exothermic, and all decomposition reactions are endothermic." Evaluate this statement. Is it always true? Justify your answer with at least one example for each part of the claim.

Explain the difference between an exothermic and an endothermic reaction, providing one example for each.

Analyze the following experimental observations and write a balanced chemical equation for each reaction described: (a) Heating a white crystalline solid, lead nitrate, produces a yellow solid residue, brown fumes, and a colourless gas. (b) A solution of calcium hydroxide used for whitewashing turns milky when exposed to air due to the formation of a white precipitate. (c) A shiny brown metal, copper, when heated in a china dish, gets coated with a black substance.

Define oxidation and reduction in terms of oxygen. Identify the substance oxidized and the substance reduced in the reaction: $CuO(s) + H_2(g) \rightarrow Cu(s) + H_2O(l)$.

List the three forms of energy that can cause decomposition reactions and provide one balanced chemical equation as an example for any one type.

Solve the following skeletal equation for the combustion of propane gas by balancing it: $C_3H_8(g) + O_2(g) \rightarrow CO_2(g) + H_2O(l)$

Analyze the following redox reaction. Identify the substance that is oxidized and the substance that is reduced, providing a reason for your choices. $MnO_2 + 4HCl \rightarrow MnCl_2 + 2H_2O + Cl_2$

Compare and contrast displacement and double displacement reactions. Illustrate your answer with one balanced chemical equation for each, explaining the fundamental difference in how substances are exchanged.

Design a series of three simple experiments you could perform in a school laboratory to demonstrate a combination, a decomposition, and a displacement reaction. For each proposed experiment, you must: a) List the reactants. b) Write the balanced chemical equation with state symbols. c) Justify why the reaction represents the specified type.