4.1 Writing and Balancing Chemical Equations

Given the following complete ionic equation, which compound does not dissolve in water to a significant extent? Ca²⁺(aq) + 2Cl⁻(aq) + 2Ag⁺(aq) + 2NO₃⁻ → Ca²⁺(aq) + 2NO₃⁻(aq) + 2AgCl(s)

AgCl(s)

What symbol separates the reactant and product (left and right) sides of a chemical equation?

An arrow (→)

In the following formula: 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) What is the physical state of the product sodium hydroxide?

Aqueous

Special conditions necessary for a reaction are sometimes designated by writing a word or symbol above or below the equation's:

Arrow

Chemical equations must be ______ to satisfy the law of conservation of matter.

Balanced

Is the following equation balanced or unbalanced? 2H₂O → 2H₂ + O₂

Balanced

The following chemical equation is ______, meaning that equal numbers of atoms for each element involved in the reaction are represented on the reactant and product sides. CH₄ + 2O₂ → CO₂ + 2H₂O

Balanced

In the following chemical equation CH₄ + 2O₂ → CO₂ + 2H₂O Name the two reactants.

CH₄ and 2O₂

In the following chemical equation CH₄ + 2O₂ → CO₂ + 2H₂O Name the two products.

CO₂ and 2H₂O

When carbon dioxide is dissolved in an aqueous solution of sodium hydroxide, the mixture reacts to yield aqueous sodium carbonate and liquid water. Given the balanced molecular equation: CO₂(aq) + 2NaOH(aq) → Na₂CO₃(aq) + H₂O(l) Write a balanced complete ionic equation for this process.

CO₂(aq) + 2Na⁺(aq) + 2OH⁻(aq) → 2Na⁺(aq) + CO₃²⁻(aq) + H₂O(l)

When carbon dioxide is dissolved in an aqueous solution of sodium hydroxide, the mixture reacts to yield aqueous sodium carbonate and liquid water. Given the balanced molecular equation and complete ionic equation: CO₂(aq) + 2NaOH(aq) → Na₂CO₃(aq) + H₂O(l) CO₂(aq) + 2Na⁺(aq) + 2OH⁻(aq) → 2Na⁺(aq) + CO₃²⁻(aq) + H₂O(l) Write a balanced net ionic equation for this process.

CO₂(aq) + 2OH⁻(aq) → CO₃²⁻(aq) + H₂O(l)

When carbon dioxide is dissolved in an aqueous solution of sodium hydroxide, the mixture reacts to yield aqueous sodium carbonate and liquid water. Write a balanced molecular equation for this process.

CO₂(aq) + NaOH(aq) → Na₂CO₃(aq) + H₂O(l) CO₂(aq) + 2NaOH(aq) → Na₂CO₃(aq) + H₂O(l)

CaCl₂(aq) + 2AgNO₃(aq) → Ca(NO₃)₂(aq) + 2AgCl(s) In an aqueous solution, how would Ca(NO₃)₂(aq) be more realistically represented?

Ca(NO₃)₂(aq) → Ca²⁺(aq) + 2NO₃⁻(aq)

11c. From the balanced molecular equations, write the complete ionic and net ionic equations for the following: CaCO₃(s) + H₂SO₄(aq) → CaSO₄(s) + CO₂(g) + H₂O(l)

CaCO₃(s) + 2H⁺(aq) + SO₄(aq) → CaSO₄(s) + CO₂(g) + H₂O(l) (complete) CaCO₃(s) + 2H⁺(aq) + SO₄(aq) → CaSO₄(s) + CO₂(g) + H₂O(l) (net)

Write the molecular equation for the following complete ionic equation. Ca²⁺(aq) + 2Cl⁻(aq) + 2Ag⁺(aq) + 2NO₃⁻ → Ca²⁺(aq) + 2NO₃⁻(aq) + 2AgCl(s)

CaCl₂(aq) + 2AgNO₃(aq) → Ca(NO₃)₂(aq) + AgCl(s)

CaCl₂(aq) + 2AgNO₃(aq) → Ca(NO₃)₂(aq) + 2AgCl(s) In an aqueous solution, how would CaCl₂(aq) be more realistically represented?

CaCl₂(aq) → Ca²⁺(aq) + 2Cl⁻(aq)

In the following complete ionic equation, what are the spectator ions? Ca²⁺(aq) + 2Cl⁻(aq) + 2Ag⁺(aq) + 2NO₃⁻ → Ca²⁺(aq) + 2NO₃⁻(aq) + 2AgCl(s)

Ca²⁺ and 2NO₃⁻

The symbolic representation of a chemical reaction is called a:

Chemical equation

A chemical equation is a symbolic representation of a:

Chemical reaction

The word "coefficient" translates as:

"cooperating to produce a result"

The word "stoichiometry" translates as:

"element measurer"

3f. Balance the following equation: (NH₄)₂Cr₂O₇(s) → Cr₂O₃(s) + N₂(g) + H₂O(l)

(NH₄)₂Cr₂O₇(s) → Cr₂O₃(s) + N₂(g) + 4H₂O(l)

A coefficient of _____ is typically omitted from a chemical equation.

1

In the following chemical equation CH₄ + 2O₂ → CO₂ + 2H₂O What is the coefficient of CH₄?

1 (but not written)

In the following chemical equation CH₄ + 2O₂ → CO₂ + 2H₂O What is the coefficient of CO₂?

1 (but not written)

In the following chemical equation CH₄ + 2O₂ → CO₂ + 2H₂O Methane and oxygen react to yield carbon dioxide and water in a _______ ratio.

1:2:1:2

Consider the following unbalanced equation: 2H₂O → H₂ + O₂ What coefficient would you add to the hydrogen product to balance the four hydrogen atoms in the product?

2

Consider the following unbalanced equation: H₂O → H₂ + O₂ What coefficient would you add to the reactant to balance the two oxygen atoms in the product?

2

How many oxygen atoms are there on each side of the following balanced chemical equation? 2H₂O → 2H₂ + O₂

2

In the following chemical equation CH₄ + 2O₂ → CO₂ + 2H₂O What is the coefficient of H₂O?

2

In the following chemical equation CH₄ + 2O₂ → CO₂ + 2H₂O What is the coefficient of O₂?

2

CaCl₂(aq) + 2AgNO₃(aq) → Ca(NO₃)₂(aq) + 2AgCl(s) In an aqueous solution, how would 2AgNO₃(aq) be more realistically represented?

2AgNO₃(aq) → 2Ag⁺(aq) + 2NO₃⁻(aq)

Given the following complete ionic equation, what would be the net ionic equation? Ca²⁺(aq) + 2Cl⁻(aq) + 2Ag⁺(aq) + 2NO₃⁻ → Ca²⁺(aq) + 2NO₃⁻(aq) + 2AgCl(s)

2Cl⁻(aq) + 2Ag⁺(aq) → 2AgCl(s) Cl⁻(aq) + Ag⁺(aq) → AgCl(s)

Diatomic chlorine and sodium hydroxide (lye) are commodity chemicals produced in large quantities in large quantities, along with diatomic hydrogen, via the electrolysis of brine, according to the following balanced complete ionic equation: 2Na⁺(aq) + 2Cl⁻(aq) + 2H₂O(l) → 2Na⁺(aq) + 2OH⁻(aq) + H₂(g) + Cl₂(g) Write the balanced net ionic equation for this process.

2Cl⁻(aq) + 2H₂O(l) → 2OH⁻(aq) + H₂(g) + Cl₂(g)

Write a balanced equation for the reaction of ethane (C₂H₆) with oxygen to yield H₂O and CO₂ represented by the unbalanced equation: C₂H₆ + O₂ → H₂O + CO₂

2C₂H₆ + 7O₂ → 6H₂O + 4CO₂

5d. Write a balanced molecular equation describing the following chemical reaction: Water vapor reacts with sodium metal to produce solid sodium hydroxide and hydrogen gas.

2H₂O(g) + 2Na(s) → 2NaOH(s) + H₂(g)

11a. From the balanced molecular equations, write the complete ionic and net ionic equations for the following: K₂C₂O₄(aq) + Ba(OH)₂(aq) → 2KOH(aq) + BaC₂O₂(s)

2K⁺(aq) + C₂O₄²⁻(aq) + Ba²⁺(aq) + 2OH⁻(aq) → 2K⁺(aq) + 2OH⁻(aq) + BaC₂O₄(s) (complete) C₂O₄²⁻(aq) + Ba²⁺(aq) → BaC₂O₄(s) (net)

Write a balanced equation for the decomposition of ammonium nitrate to form molecular nitrogen, molecular oxygen, and water. (Hint: balance oxygen last, since it is present in more than one molecule on the right side of the equation) NH₄NO₃ → N₂ + O₂ + H₂O

2NH₄NO₃ → 2N₂ + O₂ + 4H₂O

3e. Balance the following equation: Na(s) + H₂O(l) → NaOH(aq) + H₂(g)

2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)

When carbon dioxide is dissolved in an aqueous solution of sodium hydroxide, the mixture reacts to yield aqueous sodium carbonate and liquid water. Given the balanced molecular equation, complete ionic equation, and net ionic equation: CO₂(aq) + 2NaOH(aq) → Na₂CO₃(aq) + H₂O(l) CO₂(aq) + 2Na⁺(aq) + 2OH⁻(aq) → 2Na⁺(aq) + CO₃²⁻(aq) + H₂O(l) CO₂(aq) + 2OH⁻(aq) → CO₃²⁻(aq) + H₂O(l) What is the spectator ion?

2Na⁺(aq)

Diatomic chlorine and sodium hydroxide (lye) are commodity chemicals produced in large quantities in large quantities, along with diatomic hydrogen, via the electrolysis of brine, according to the following balanced equation: electricity 2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + H₂(g) + Cl₂(g) Write a balanced complete ionic equation for this process.

2Na⁺(aq) + 2Cl⁻(aq) + 2H₂O(l) → 2Na⁺(aq) + 2OH⁻(aq) + H₂(g) + Cl₂(g)

Write a balanced equation for the reaction of molecular nitrogen (N₂) and oxygen (O₂) to form dinitrogen pentoxide. N₂ + O₂ → N₂O₅

2N₂ + 5O₂ → 2N₂O₅

3b. Balance the following equation: Cu(s) + HNO₃(aq) → Cu(NO₃)₂(aq) + H₂O(l) + NO(g)

3Cu(s) + 8HNO₃(aq) → 3Cu(NO₃)₂(aq) + 4H₂O(l) + 2NO(g)

How many hydrogen atoms are there on each side of the following balanced chemical equation? 2H₂O → 2H₂ + O₂

4

3d. Balance the following equation: Fe(s) + O₂(g) → Fe₂O₃

4Fe(s) + 3O₂(g) → 2Fe₂O₃

A number placed in front of symbols or formulas in a chemical equation to indicate their relative amount is called a:

Coefficient

It is common practice to use the smallest possible whole-number ______ in a chemical equation.

Coefficients

The relative numbers of reactant and product species are represented by ________ (numbers placed immediately to the left of each formula).

Coefficients

______ represent the relative numbers of reactants and products and products and may be correctly interpreted as ratios.

Coefficients

An equation for an ionic reaction that explicitly represents all the dissolved ions results in a:

Complete ionic equation

Which one of the following equations for ionic reactions is the most detailed: molecular equation, complete ionic equation, or net ionic equation?

Complete ionic equation

Which one of the following equations for ionic reactions represents what really happens in a flask: molecular equation, complete ionic equation, or net ionic equation?

Complete ionic equation

Chemical equations must be balanced to satisfy the law of:

Conservation of matter

5b. Write a balanced molecular equation describing the following chemical reaction: Gaseous butane, C₄H₁₀, reacts with diatomic oxygen gas to yield gaseous carbon dioxide and water vapor.

C₄H₁₀(g) + O₂(g) → 4CO₂(g) + 5H₂O(g)

A reaction carried out by heating may be indicated by the upper Greek letter _____ (∆) over the arrow in a chemical equation.

Delta

When ionic compounds dissolve in water, they _____ into their constituent ions, which are subsequently dispersed homogenously throughout the resulting solution.

Dissociate

Ionic compounds dissolved in water are, therefore, more realistically represented as:

Dissociated ions

The following chemical equation is balanced, meaning that _____ numbers of atoms for each element involved in the reaction are represented on the reactant and product sides. CH₄ + 2O₂ → CO₂ + 2H₂O

Equal

To ensure that a chemical equation is balanced, the sums of the numbers of atoms on both sides must be:

Equal

In the following formula: 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) What is the physical state of the product molecular hydrogen?

Gas

Greek letter Delta ∆ that ________ must be added to make a reaction go.

Heat

The following chemical equation contains a ∆ over the →. What does the ∆ represent? ∆ CaCO₃(s) → CaO(s) + CO₂(g)

Heating

3c. Balance the following equation: H₂(g) + I₂(s) → HI(s)

H₂(g) + I₂(s) → 2HI(s)

The reactants are placed on the ______ side of the chemical equation.

Left

In the following formula: 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) What is the physical state of the reactant water?

Liquid

5c. Write a balanced molecular equation describing the following chemical reaction: Aqueous solutions of magnesium chloride and sodium hydroxide react to produce solid magnesium hydroxide and aqueous sodium chloride.

MgCl₂(aq) + 2NaOH(aq) → Mg(OH)₂(s) + 2NaCl(aq)

CaCl₂(aq) + 2AgNO₃(aq) → Ca(NO₃)₂(aq) + 2AgCl(s) This balanced equation, derived in the usual fashion, is called a ___________ because it doesn't explicitly represent the ionic species that are present in solution.

Molecular equation

Which one of the following equations for ionic reactions tells you what to prepare in lab: molecular equation, complete ionic equation, or net ionic equation?

Molecular equation

Diatomic chlorine and sodium hydroxide (lye) are commodity chemicals produced in large quantities in large quantities, along with diatomic hydrogen, via the electrolysis of brine, according to the following unbalanced equation: electricity NaCl(aq) + H₂O(l) → NaOH(aq) + H₂(g) + Cl₂(g) Write a balanced molecular equation for this process.

NaCl(aq) + H₂O(l) → NaOH(aq) + H₂(g) + Cl₂(g) 2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + H₂(g) + Cl₂(g)

Cl⁻(aq) + Ag⁺(aq) → AgCl(s) This ______ indicates that solid silver chloride may be produced from dissolved chloride and silver(I) ions, regardless of the source of these ions.

Net ionic equation

Which one of the following equations for ionic reactions ignores the spectator ions and isolates the unique product: molecular equation, complete ionic equation, or net ionic equation?

Net ionic equation

A coefficient is a ______ placed in from of symbols or formulas in a chemical equation to indicated their relative amount.

Number

Reduce the coefficients to the smallest possible integers in the following balanced equation: 3N₂ + 9H₂ → 6NH₃

N₂ + 6H₂ → 3NH₃

3a. Balance the following equation: PCl₅(s) + H₂O(l) → POCl₃(l) + HCl(aq)

PCl₅(s) + H₂O(l) → POCl₃(l) + 2HCl(aq)

11b. From the balanced molecular equations, write the complete ionic and net ionic equations for the following: Pb(NO₃)₂(aq) + H₂SO₄(aq) → PbSO₄(s) + 2HNO₃(aq)

Pb²⁺(aq) + 2NO₃⁻(aq) + 2H⁺(aq) + SO₄²⁻(aq) → PbSO₄(s) + 2H⁺(aq) + 2NO₃⁻ (complete) Pb²⁺(aq) + SO₄²⁻(aq) → PbSO₄(s) (net)

What signs separate individual reactant and product formulas in a chemical equation?

Plus signs (+)

The substances generated by the reaction are called _____, and their formulas are placed on the right side of the equation.

Products

3h. Balance the following equation: PtCl₄(s) → Pt(s) + Cl₂(g)

PtCl₄(s) → Pt(s) + 2Cl₂(g)

3g. Balance the following equation: P₄(s) + Cl₂(g) → PCl₃(l)

P₄(s) + 6Cl₂(g) → 4PCl₃(l)

Coefficients represent the relative numbers of reactants and products and may be correctly interpreted as:

Ratios

The substances undergoing reaction are called ______, and their formulas are placed on the left side of the equation.

Reactants

The products are placed on the ____ side of the chemical equation.

Right

In the following formula: 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) What is the physical state of the reactant sodium?

Solid

In a complete ionic equation, ions whose presence is required to maintain charge neutrality but are neither chemically nor physically changed by the process are known as:

Spectator ions

What are eliminated from a complete ionic equation to a yield a more succinct representation called a net ionic equation?

Spectator ions

Reaction _____ is symbolizing chemical reactions using chemical equations, classifying chemical reactions by their patterns of reactivity, and determining quantitative relations between the amounts of substances involved in chemical reactions.

Stoichiometry

The science of calculating the quantities of chemical elements involved in chemical reactions is called:

Stoichiometry

Balancing by inspection is a trial and error method. True or False?

True

In the following chemical equation CH₄ + 2O₂ → CO₂ + 2H₂O Methane and oxygen react to yield carbon dioxide and water in a 1:2:1:2 ratio. This ratio may be interpreted with regard to any amount (e.g.molecules, dozens, moles). True or False?

True

Ionic compounds that do not dissociate in water are not water soluble. True or False?

True

Regardless of the absolute numbers of molecules involved, the ratios between numbers of molecules of each species that react (the reactants) and molecules of each species that form (the products) are the same and are given by the chemical reaction equation. True or False?

True

When writing net ionic equations, you must follow the convention of using the smallest possible integers as coefficients. True or False?

True

Is the following equation balanced or unbalanced? H₂O → H₂ + O₂

Unbalanced

Given the abundance of _____ on earth, it stands to reason that a great many chemical reactions take place in aqueous media.

Water

CaCl₂(aq) + 2AgNO₃(aq) → Ca(NO₃)₂(aq) + 2AgCl(s) Unlike CaCl₂, 2AgNO₃, and Ca(NO₃)₂, AgCl does not dissolve in water to a significant extent, as signified by its physical state notation,:

s

In the following chemical equation CH₄ + 2O₂ → CO₂ + 2H₂O What symbol separates the reactants and products and indicates the direction of the reaction?

→

5a. Write a balanced molecular equation describing the following chemical reaction: Solid calcium carbonate is heated and decomposes to solid calcium oxide and carbon dioxide gas.

∆ CaCO₃(s) → CaO(s) + CO₂(g)