CHEM 1062 - Chapter 7 Study Guide

If the solute is changed chemically, then it is a _____ ______. If the solute doesn't change chemically, it is not a _____ _____.

chemical reaction, chemical reaction

Using a molecular-level explanation, explain the difference between a chemical change and a phase change.

Chemical changes involve the breaking and forming of chemical bonds. There is a rearrangement of atoms where the connections between atoms change. Additionally, there is a change in the location of valence electrons. A phase change doesn't alter the chemical composition of a substance, but changes the state of matter instead. Phase changes involve overcoming intermolecular forces.

What are the molecular structural features that lead to basic properties in a molecule?

lone pair of electrons that can be donated, NH2 group, contain a nitrogen or oxygen atom, after losing an electron pair, the remaining structure is stable

What are the molecular structural features that lead to acidic properties in a molecule?

presence of hydrogen atoms (especially ones bonded to electronegative atoms), presence of an OH or COOH group, a structure that is stable after gaining an electron pair

Why are features that lead to acidic or basic properties in a molecule important?

knowing these features helps predict how substances will behave in chemical reactions

HCl, HBr, HI, HNO3, and H2SO4 are all examples of what?

Strong Acids

Any group 1 or group 2 metals with hydroxide ions, such as NAOH or KOH are examples of what?

Strong Bases

A _______ acid or base completely dissociates into ions in solution.

strong

A _____ acid or base partially dissociates in solution.

weak

A _______ solution has a relatively small amount of solute compared to the amount of solvent.

dilute

A ______ solution has a large amount of solute relative to the solvent.

concentrated

What factors contribute to the relative strength of acids?

the more electronegative the atom bonded to the hydrogen, the stronger the acid, weaker bonds between the hydrogen and the rest of the molecule means a stronger acid, a more negative/ exothermic enthalpy change indicates a stronger acid

What factors contribute to the relative strength of bases?

the less electronegative the atoms with lone pairs of electrons, the stronger the base (more willing to share pairs), a more negative/ exothermic enthalpy change indicates a stronger base

What is the Arrhenius acid-base model?

An acid dissolves in water to give H+, and a base dissolves in water to give OH-. Limitations were that it was restricted to aqueous solutions and doesn't work for acid-base reactions that don't produce H+ or OH-.

What is the equation for calculating the pH when given the H3O+ concentration?pH = -log(H3O+)

pH = -log(H3O+)

What is the Bronsted-Lowry acid-base model?

An acid is a proton donor and a base is a proton acceptor. This theory is more inclusive than the Arrhenius model because it includes non-aqueous systems. It also introduces the concept of conjugate acids and bases.

What is the Lewis Acid and Base model?

An acid is an electron pair acceptor and a base is an electron pair donor. Encompasses the Bronsted-Lowry and Arrhenius theory, but has the base as the initiator of the reaction.

What is the equation for calculating concentration of H3O+ when given pH?

[H3O+]=10−pH

At 25 degrees Celsius, in pure water, the product of H3O+ and -OH is equal to what?

1 x 10^-14

What is the equation for percent ionization?

part/ whole x 100

What is the sum of pH and pOH in an aqueous solution at 25 degrees Celsius?

14

What's the difference between acid-base reactions and redox-reactions?

Acid-base reactions have an electron pair donation/ acceptance with no change in oxidation states. On the other hand, redox reactions are electron transfers with a change in oxidation states of reactants.

How would you use bond energies to predict and calculate enthalpy changes in reactions?

identify the bonds broken and formed, use a table to find bond energies, and take the energy of the bond broken and subtract the energy of the bonds formed.

What is a neutralization reaction? How do you identify one?

When an acid and base react to form water and a salt. To identify, look for the presence of an acid (H+ ions) and a base (OH- ions), ensure that the reaction produces a salt and water, and see if the reaction is an exothermic process.

What is autoionization?

Autoionization is where water molecules donate and accept protons, allowing it to act as both an acid and a base.

What is Kw? What is its value at 25 degrees Celsius?

The equilibrium constant for the autoionization of water. Helps with calculating the pH and pOH of aqueous solutions. Kw = 1.0 x 10^-14.

What's the relationship between -OH and H3O+ in aqueous solution?

Related through the Kw factor that (H3O+)(OH-) = 1.0 x 10^-14

What is the range for an acidic solution on the pH scale? How about a basic solution? What's the pH of a neutral solution?

<7 for acidic, >7 for basic, 7 for neutral

H+ ions are _____ (acidic/ basic) and OH- ions are _____ (acidic/ basic).

acidic, basic

How to identify conjugate acid-base pairs?

An acid forms its conjugate base when it donates a proton/ accepts an electron pair, and a base forms its conjugate acid when it accepts a protons/ donates an electron pair.

The oxidation number of elements in their elemental form is ____. The oxidation number of monatomic ions (ions with a charge) is equal to their _____. The sum of oxidation states must equal ____.

0, charge, 0

Oxidation is the ____ ____ _____ and reduction is the ____ ____ _____.

loss of electrons, gain of electrons

The oxidizing agent is the substance that is _______ and the reducing agent is the substance that is _______.

reduced, oxidized

A nucleophile (nucleus-loving) is a Lewis ______. An electrophile (electron-loving) is a Lewis ______.

base, acid

H-F would be a weaker acid because it has a ______ (strong/ weak) bond. There is better overlap between the ______ _______ of H and F because they are most similar in size.

strong, bonding orbitals

Acid strength ______ (increases, decreases) down a group because the difference in size between H and X gets _______ (bigger, smaller) down the group, meaning there is less overlap between H and X orbitals and the bond is ______ (stronger, weaker) and _______ (easier, harder) to break.

increases, bigger, weaker, easier

If a base is less electronegative than another base, it is ______. This is because it is more willing to share electrons.

stronger

A solution with a higher concentration of hydronium (H3O+) ions than pure water is ______. A solution with a higher concentration of hydroxyl (OH-) ions is _____.

acidic, basic

Bond _____ releases energy to the surroundings, and bond _______ requires energy input from the surroundings.

formation, breaking