Chemistry: Balancing Equations, Redox, and Solubility Guidelines

What is a chemical equation?

An expression using symbols and formulas to represent a chemical reaction.

What is a reactant?

A substance that undergoes change in a chemical reaction, written on the left side of the reaction arrow.

What is a product?

A substance formed in a chemical reaction, written on the right side of the reaction arrow.

What does the law of conservation of mass state?

Mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations.

How must a chemical equation be balanced?

The numbers and kinds of atoms must be the same on both sides of the reaction arrow.

What is a coefficient in a chemical equation?

A number placed in front of a formula to balance a chemical equation.

What symbols indicate the physical state of substances in a chemical equation?

(s) = solid, (l) = liquid, (g) = gas, (aq) = dissolved in aqueous solution.

What is the first step in balancing a chemical equation?

Write an unbalanced equation using the correct formulas for all reactants and products.

What is the second step in balancing a chemical equation?

Add appropriate coefficients to balance the numbers of atoms of each element.

What is the third step in balancing a chemical equation?

Check the equation to ensure the numbers and kinds of atoms on both sides are the same.

What is the fourth step in balancing a chemical equation?

Ensure the coefficients are reduced to their lowest whole-number values.

In the reaction of methane (CH4) with oxygen (O2), what is the balanced equation?

CH4 + 2O2 → CO2 + 2H2O.

What is the importance of using diatomic molecules in chemical equations?

Elements like hydrogen and oxygen must be written as H2 and O2 because they exist as diatomic molecules.

How do you treat a polyatomic ion in a chemical equation?

It is treated as a single unit if it appears on both sides of the equation.

What is the Haber process?

An important industrial reaction where elemental nitrogen and hydrogen combine to form ammonia.

What is the unbalanced equation for the Haber process?

N2(g) + H2(g) → NH3(g).

What do you do if an element exists in elemental form in a chemical equation?

Leave it until last when balancing the equation.

What is the purpose of balancing chemical equations?

To ensure that the mass of reactants equals the mass of products, adhering to the law of conservation of mass.

What is the significance of the coefficients in a balanced equation?

They indicate the relative amounts of reactants and products involved in the reaction.

What is the role of subscripts in chemical formulas?

Subscripts indicate the number of atoms of each element in a molecule and cannot be changed.

What is the result of not balancing a chemical equation?

It would violate the law of conservation of mass, leading to incorrect calculations.

What is the general format for writing a chemical equation?

Reactants on the left, products on the right, with an arrow indicating the direction of the reaction.

What is the importance of checking the balance of an equation?

To confirm that the equation accurately represents the conservation of mass in the reaction.

What happens if you change the subscripts in a chemical formula?

It changes the identity of the substances in the reaction.

What is the significance of balancing the number of hydrogen atoms in the combustion of methane?

It ensures that the reaction conserves mass and correctly represents the products formed.

What is the final balanced equation for the combustion of methane?

CH4 + 2O2 → CO2 + 2H2O.

What is the balanced equation for the reaction of nitrogen and hydrogen to form ammonia?

N2(g) + 3H2(g) → 2NH3(g)

How do you balance the nitrogen atoms in the equation N2(g) + H2(g) → NH3(g)?

Add a coefficient of 2 in front of NH3 on the right side.

What must be done to balance the hydrogen atoms in the equation N2(g) + 3H2(g) → 2NH3(g)?

Add a coefficient of 3 in front of H2 on the left side.

What is the significance of reducing coefficients to their lowest whole-number values?

It ensures the simplest representation of the balanced equation.

What is the balanced equation for the decomposition of sodium chlorate (NaClO3)?

2NaClO3 → 2NaCl + 3O2

What is a precipitation reaction?

A process in which an insoluble solid called a precipitate forms when reactants are combined in an aqueous solution.

What happens when lead (II) nitrate is mixed with potassium iodide?

It forms a brilliant yellow lead (II) iodide precipitate.

What determines whether a precipitation reaction will occur?

The solubilities of the potential products.

What is the solubility of sodium chloride at room temperature?

Approximately 35 g/100 g H2O.

What is a spectator ion?

An ion that appears unchanged on both sides of a reaction arrow and plays no role in the reaction.

What is the net ionic equation for the reaction of CdCl2 and (NH4)2S?

Cd2+(aq) + S2-(aq) → CdS(s)

What is an acid-base neutralization reaction?

A process in which an acid reacts with a base to yield water plus an ionic compound called a salt.

What does an acid provide in water?

H+ ions.

What does a base provide in water?

OH- ions.

What is produced when an acid and a base react?

Water and a salt.

What is the balanced equation for the neutralization reaction of HBr and Ba(OH)2?

HBr + Ba(OH)2 → BaBr2 + H2O

What is the net ionic equation for the neutralization of KOH and HNO3?

OH-(aq) + H+(aq) → H2O(l)

What type of reaction occurs when H+ from an acid combines with OH- from a base?

A neutralization reaction.

What is the result of combining the anion from an acid with the cation from a base?

It yields a salt.

What is the general formula for a neutralization reaction?

Acid + Base → Water + Salt.

What is the role of coefficients in a balanced chemical equation?

They indicate the relative amounts of reactants and products.

What happens to the coefficients when balancing an equation?

They may need to be multiplied by a common factor to achieve the lowest whole-number values.

What is the significance of checking that the numbers and kinds of atoms are the same on both sides of a reaction?

It confirms that the equation is balanced.

What is the product of the neutralization reaction between HBr and Ba(OH)2?

BaBr2 and water.

What is the first step in writing a balanced equation for a decomposition reaction?

Write an unbalanced equation using the correct formulas for all reactants and products.

What is produced when HBr reacts with Ba(OH)2?

Water (H2O) and barium bromide (BaBr2)

What is the net ionic equation for the reaction of HBr and Ba(OH)2?

OH− (aq) + H+ (aq) → H2O (l)

What are the spectator ions in the reaction between HBr and Ba(OH)2?

Ba2+ (aq) and Br− (aq)

What is produced in a neutralization reaction involving an acid and a carbonate?

Water, a salt, and carbon dioxide (CO2)

What happens to H2CO3 in a reaction with carbonate ions?

It decomposes to yield H2O and CO2.

What is the general reaction for an acid reacting with a bicarbonate?

HA (aq) + MHCO3 (aq) → H2O (l) + MA (aq) + CO2 (g)

What defines a redox reaction?

Reactions in which electrons are transferred from one atom to another.

What does oxidation refer to in modern chemistry?

The loss of one or more electrons.

What does reduction refer to in modern chemistry?

The gain of one or more electrons.

What is an example of a redox reaction involving copper and silver?

Copper wire reacts with aqueous Ag+ ions, becoming coated with metallic silver.

What is a reducing agent?

A substance that loses electrons and causes reduction.

What is an oxidizing agent?

A substance that gains electrons and causes oxidation.

What are alkali metals known for in redox reactions?

They are powerful reducing agents.

What are reactive nonmetals known for in redox reactions?

They are powerful oxidizing agents.

What is corrosion?

The deterioration of a metal by oxidation, such as rusting.

What is combustion?

The burning of a fuel by rapid oxidation with oxygen.

What is respiration in terms of redox reactions?

The process of breathing and using oxygen for biological redox reactions.

What does oxidation number indicate?

Whether an atom is neutral, electron-rich, or electron-poor.

What is the oxidation number of an atom in its elemental state?

0

What is the oxidation number of a monatomic ion?

Equal to its charge.

What is the usual oxidation number of hydrogen?

+1

What is the usual oxidation number of oxygen?

-2

What is the sum of oxidation numbers in a neutral compound?

0

In TiCl4, what is the oxidation number of titanium?

+4

In the reaction 2 Fe2O3 + 3 C → 4 Fe + 3 CO2, which reactant is oxidized?

Carbon (C)

In the reaction 2 Fe2O3 + 3 C → 4 Fe + 3 CO2, which reactant is reduced?

Iron (Fe2O3)

What is the role of carbon in the reaction producing iron from Fe2O3?

It is the reducing agent.

What is the role of Fe2O3 in the reaction producing iron from Fe2O3?

It is the oxidizing agent.