General Chemistry - TRP Review Questions

Question 1

What are the three fundamental particles of matter? And which determines the identity of an element?

Answer 1

Neutron

Proton

Electron

The # of protons determines the identity

Question 2

Isotopes differ by the number of which fundamental particle?

Which particle(s) is the mass number of an element determined by?

Answer 2

Same number of protons, different number of neutrons. Differ by the number of neutrons.

of protons plus # of neutrons in an atom

Question 3

There are two types of ions. Identify them by name and their type of charge

Question 4

What letter stands for the principal quantum number? What is the range of possible values for this number?

Define the principal quantum number

Answer 4

The letter “n”

n = 1 to n=infinite

The principal quantum number is the quantum number denoted by n and which indirectly describes the size of the electron orbital. It is always assigned an integer value (e.g., n = 1, 2, 3…), but its value may never be 0. An orbital for which n = 2 is larger, for example, than an orbital for which n = 1. Energy must be absorbed in order for an electron to be excited from an orbital near the nucleus (n = 1) to get to an orbital further from the nucleus (n = 2).

The principal quantum number is cited first in the set of four quantum numbers associated with an electron. The principal quantum number has the greatest effect on the energy of the electron. It was first designed to distinguish between different energy levels in the Bohr model of the atom but remains applicable to the modern atomic orbital theory

Question 5

The ground state electron configuration of any element can be determined by following three rules of electron filling.

What are they and how do they determine the location of electrons in an atom?

Answer 5

The Aufbau Principle: fill lower enegy levels and sublevels before adding electrons to higher energy (sub)levels.

Pauli Exclusion Principle: there are a maximum of 2 electrons per orbital, and they must have opposite spins

Hund’s Rule: half fill orbitals of equal energy before pairing electrons in any one orbital in a given subshell.

Question 6

State the three properties of electromagenetic radiation:

Answer 6

Frequency

Wavelength

Energy

Question 7

Define Quantized

Answer 7

Only comes in certain discrete sizes (for ex: cannot be divide by 2. Electron mass is quantized, cannot be broken in half so cannot be divided in half)

Question 8

Name the three main types of nuclear decay from least to most damaging to tissue:

Answer 8

(least damaging) Alpha < Beta < Gamma (most damaging)

Question 9

One type of nuclear decay has three different modes. What are they?

Answer 9

Beta: B^- (normal beta decay)

B⁺ : positron emission

EC: Electron capture

Question 10

What are the five periodic trends?

Answer 10

Electronegativity

Atomic size

Electron affinity

First ionization energy

Acidity/Basicity

Question 11

What are the 3 kinds of covalent bonds?

Answer 11

Normal (which can be polar or nonpolar)

Metallic

Coordinate covalent bonds

Question 12

Give 2 other names for Lewis Bases

Answer 12

Ligand, nucleophile, or chelator

Question 13

What three geometric family names are associated with each type of hybridized orbitals?

Answer 13

Linear : sp

Trigonal planar: sp²

Tetrahedral: sp³

Question 14

Name the various intermolecular forces, from strongest to weakest

Answer 14

Strongest

Hydrogen bonding

Dipole-dipole forces

London dispersion forces

Weakest

Question 15

What are the phases of matter (disregarding plasma)?

Answer 15

Gas
Liquid

Solid

Question 16

When energy is added to a substance, that energy can be used to do one of two physical things. What are they?

Answer 16

Increase the temperature (increase Kinetic Energy)

Cause a phase change (Increase Potential Energy)

Question 17

What two things does vapor pressure depend on?

Answer 17

Temperature and intermolecular forces

Question 18

When does a liquid boil?

Answer 18

When the hydrogen bonds or other intermolecular forces no longer can hold molecules together.

When vapor pressure of liquid = atmospheric pressure

Question 19

The phase of a substance depends on what two properties besides intermolecular forces?

Answer 19

Temperature

Pressure

Question 20

What assumptions do we make about ideal gases?

Answer 20

Take up no volume

and

Experience no intermolecular forces

Question 21

What do the constants a and b accound for in the van der waals equation for real gases?

What is the van der waals equation?

Answer 21

The constant a accounts for the intermolecular forces between gas molecules and b accounts for the molecular volume of the gas particles

Question 22

What conditions are indicated by the letter STP?

Answer 22

Standard Temperature and Pressure:

Temperature = 0 degrees Celsius

Pressure = 1 atm

Question 23

What is the volume of 1 mole of an ideal gas at STP?

Answer 23

22.4 L

Question 24

Describe at a molecular level what happens to a solid when it dissolves

Answer 24

Dissociation

Solvent molecules interact with ions

(solute particles are separated and encapsulated by solvent molecules such that the solute is observed to dissolve)

Question 25

Define *electrolyte*

Question 26

What is the difference between an intermediate and a transitions state?

Answer 26

An **intermediate** is found at local energy minima along a reaction coordinate while **transition states** are at local energy maxima along a reaction coordinate. **Transition states** are the highest energy species in a reaction because bonds are breaking and forming, so it cannot be isolated from a reaction.

Question 27

What is the minimum energy required to start a reaction?

Answer 27

The **activation energy E_a** must be reached before a reaction can proceed.

Question 28

What three properties affect the rate of a reaction?

Answer 28

Temperature [Concentration] (or for gases, partial pressure) Activation Energy

Question 29

What are the two ways to determine the order of a rate law?

Answer 29

1. A multitrial experiment in which the concentration of one reagent is changed over time 2. Looking at the rate-determining step in a previously proposed mechanism CAN ONLY BE DETERMINED EXPERIMENTALLY

Question 30

What does it mean for a reaction to be at equilibrium?

Answer 30

The rate of the reaction in the forward direction is equal to the rate of reaction in the reverse direction (or the concentrations of reactants and products do not change with respect to time)

Question 31

What types of substances are included in an equilibrium constant (K) expression? What types of substances are excluded?

Answer 31

gases and aqueous solutions are included liquids and solids are excluded (or if solution has an extremely small concentration can treat as liquid)

Question 32

State the three ways to disturb or stress a chemical equilibrium

Answer 32

1. Add or remove heat 2. Change volume (aka add or remove pressure) 3. Add or remove product or reactant (change concentration)

Question 33

What is the only way to change the equilibrium contant, K value?

Answer 33

Change the temperature

Question 34

Name the strong acids and strong bases:

Answer 34

_Strong Acids_ HCl HBr HI HNO₃ HClO₄ H₂SO4 _Strong Bases_ Group 1 Hydroxides (ex: NaOH) Ba/Sr/Ca hydroxides Metal amides

Question 35

Define a *conjugate pair*

Answer 35

Two molecules/ions that differ by one H⁺

Question 36

What is the pH scale? Where do acids and bases fall on the scale?

Answer 36

pH scale measures acidity and basicity of molecules. Based on hydrogen Acids are low numbers (less than 7) Bases are high numbers (greater than 7) 7 is neutral

Question 37

How is the pH of a strong acid calculated?

Answer 37

pH = -log[H⁺] Which is the same as -log[acid] since strong acids *completely dissociate*

Question 38

Give three reasons why a titration might be performed:

Answer 38

1. To determine the concentration of an unknown acid or unknown base 2. to create a buffer 3. to determine the pK_a (or pK_b) of an unknown weak acid (or weak base) nad perhaps thereby identify the acid or base as well

Question 39

What is the **equivalence point** of a titration?

Answer 39

The point at which pH = pK_a

Question 40

What is a buffer?

Answer 40

A solution that resists change to pH

Question 41

What happens to the pH of a buffer when it is diluted? When concentrated?

Answer 41

The pH does not change upon the addition or removal of solvent because relative concentrations of the acid and conjugate base in solution change proportionately, so their ratio does not change.

Question 42

identify the **standard state conditions** for temperature and pressure:

Answer 42

25 degrees Celsius 1 ATM

Question 43

When is the entropy of a subsance equal to zero?

Answer 43

When a pure element is solid at absolute zero (0 degrees Kelvin)

Question 44

Which process requires energy (is endothermic), breaking a bond or forming a bond?

Answer 44

Breaking a bond (absorbs energy) is **endothermic** Forming a bond (releases energy) is **exothermic**

Question 45

Name the two parts of all electrochemical reaction, and define them based on electron transfer.

Answer 45

Oxidation: Lose electrons Reduction: Gain electrons

Question 46

What does a positive reduction potential indicate?

Answer 46

The reduction half-reaction is spontaneous while the associated oxidation half-reaction (the reverse reaction) is non-spontaneous

Question 47

Which electrochemical cell type produces electricity from sponaneous chemical reactions, an electrolytic cell or a galvanic cell?

Answer 47

**Galvanic cells** use spontaneous reactions to produce electricity, which **electrolytic cells** use electricity to force nonspontaneous reactions to occur (Need to look further into these concepts)

Question 48

What is the sign of each electrode in a galvanic cell? An electrolytic cell?

Answer 48

In a **galvanic cell**, the cathode is positive and the anode is negative. In an **electrolytic cell**, the electrode signs are reversed. (WHY?)

Question 49

Give two examples of elements that do not obey the Aufbau Principle

Answer 49

Chromium (Cr) and its family members or Copper (Cu) and its family members (why don't they obey it?)

Question 50

Which electrons do transition metal atoms lose first when they are ionized?

Answer 50

The electrons from the "s" orbital (**valence s electrons**)

Question 51

Explain the difference between **paragmagnetics** and **diamagnetic** elements. Give examples of each:

Answer 51

**Paramagnetic:** unpaired electron Example: N **Diamagnetic:** paired electron Example: Ne (or any element with filled orbital subshell)

Question 52

What happens to the spacing between successively higher energy levels in an atom as you move farther from the nucleus?

Answer 52

The spacing decreases | (why is this important?)

Question 53

Describe each kind of nuclear decay

Answer 53

**Alpha** Nucleus emits a helium nucleus (two protons and two neutrons **Beta** B^- : a neutron converts into a proton and an electron B⁺ : a proton converts into a neutron and a positron (e⁺ - which is emitted) **Electron Capture** A proton in the nucleus captures an inner-shell electorn and converts it into a neutron **Gamma** Excited nucleus drops to lower energy state by emitting a gamma photon

Question 54

What type of mathematical relationship is associated with radioactive decay?

Answer 54

Radioactive elements decay **exponentially** with respect to time

Question 55

Why is the mass of the a nucleus not equal to the individual protons and neutrons that comprise it?

Answer 55

**Binding Energy** or **mass defect** Energy is release upon binding results in less energy that sum of constitutent parts (**The binding energy that is released when the nucleons are bound together in the nucleus comes from the mass defect according to E=mc²**)

Question 56

Define each periodic trend

Answer 56

**Atomic Radius:** Extent of the valence electrons of an atom. **Ionization Energy:** Energy required to remove a mole of valence electrons from a mole of gaseous atoms of a given element. **Electron Affinity:** Energy associated with adding a mole of electrons to the valence shell of a mole of gaseous atoms of a given element. **Electronegativity:** A measure of the amount of "pull" an atom has on shared valence electons in a bond. **Acidity :** the tendency for a molecule to give up a hydrogen atom

Question 57

Which three periodic trends follow the same pattern? What are the trends? (need to answer)\* Why do the three trends all agree?

Answer 57

**First Ionization Energy** **Electron Affiinity** **Electronegativity** (what are these trends on the periodic table?)\* They are all inversely related to atomic size (and thus, follow the opposite trend from atomic size)

Question 59

What charge is generally associated with larger ions? With smaller ions?

Answer 59

Negative charge - larger ions Positive charge - smaller ions

Question 60

Name at least three properties of liquids that depend on intermolecular forces:

Answer 60

1. Solubility 2. Vapor Pressure 3. Boiling Point Temperature 4. Melting Point Temperature 5. Viscosity 6. Surface Tension

Question 61

What quantity is specified by the average kinetic energy of the molecules of a substance?

Answer 61

Temperature

Question 62

In which phase do molecules have the most energy?

Answer 62

In the **gas phase** (if plasma is ignored)

Question 63

At a given temperature, which gas molecules travel faster? Those with small molecular weights or those with large molecular weights?

Answer 63

Those with small molecular weights will travel faster

Question 64

What are the official names for the six phase changes?

Answer 64

Sublimation Condensation Freezing Vaporization Melting (Fusion) Deposition

Question 65

State the sign of ΔH and ΔS for each of the six phase changes, and rank them from highest magnitude to lowest

Answer 65

Fusion (melting): ΔH(+) ΔS(+) Freezing ΔH(-) ΔS(-) Condensation ΔH(-) ΔS(-) Vaporization ΔH(+) ΔS(+) Sublimination ΔH(++) ΔS(++) Deposition ΔH(--) ΔS(--) ΔH_dep \> ΔH_cond \> ΔH_freeze \> 0 ΔS_sub \> ΔS_vap \> ΔS_fus \> 0 the ΔS and ΔH values are equal and opposite in sign based on their phase change. For example, ΔH_sub = | ΔH_dep |

Question 66

What happens at a molecular level when a substance changes phase?

Answer 66

Intermolecular forces are formed or broken

Question 67

What is usually the densest phase of matter?

Answer 67

Usually solid, however the main exception is: in water we find that liquid phase is denser than solid phase.

Question 68

What property is used to measure the amount of a given gas in a mixture of gases?

Answer 68

Partial Pressure

Question 69

Give an examples of a gas that most closesly approaches ideal behavior:

Answer 69

Helium (why?) (What others?)

Question 70

What temperature and pressure conditions allow most gases to behave most ideally?

Answer 70

High temperatures and low pressures (or large volumes)

Question 71

What usually happens to the solubility of solids in liquids as the temperature is increased? Why does this happen?

Answer 71

The solubility increases because solute-solute intermolecular forces weaken as solute molecules spread out due to increased vibration/kinetic energy

Question 72

How does the solubility of gases in liquids depend upon temperature and pressure?

Answer 72

The solubility of gases decreases with increasing temperature, but increases with increasing pressure

Question 73

Which ions always result in a soluble salt? Which ions generally form insoluble salts?

Answer 73

Group 1, ammonia, nitrate, acetate, and bicarbonate salts are always soluble in water. Pb, Ag, and Hg salts are generally solible in water, unless paired with the anions previously mentioned

Question 74

What do catalysts do and how do they do it?

Answer 74

A catalyst increases the rate at which a reaction reaches equilibrium by **lowering** the activation energy

Question 75

What does the order of the **rate law** say about the reaction mechanism?

Answer 75

The number of molecules colliding in the **rate-determining step**

Question 76

How does the rate of a chemical reaction change with temperature?

Answer 76

As temperature increases, rate increases As temperature decreases, rate decreases **Reaction rate ALWAYS increases with increasing temperature**

Question 77

How will a catalyst affect a system that is at equilibrium

Answer 77

It won't affect it (**it won't do anything as a catalyst only helps a reaction get to equilibrium by lowering the activation energy**)

Question 78

How does the reaction quotient, Q, help determine if a reaction is at equilibrium?

Answer 78

If K = Q, then the reaction is at equilibrium. If K \< Q, the reaction will proceed in the reverse direction to reach equilibrium If K \> Q, the reaction will proceed in the forward direction to reach equilibrium (**Look at the operand; it points in the direction of the shift if K is ALWAYS kept on the left side)** **K =\> Q** (if K greater than Q, goes forward)

Question 79

What does the term *strong* mean in relation to an acid/base/electrolyte? What about the term *weak*?

Answer 79

Strong: dissociates completely (K \> 1) Weak: partial dissociation (K \< 1) All soluble salts are strong electrolytes, as are strong acids and strong bases. Weak acids and weak bases are weak electrolytes (do not completely dissocatiate)

Question 80

What equilibrium exists in water that is shifted by the addition of an acid or a base, and what is the value of K for this reaction at standard conditions?

Answer 80

The **autoionization of water**, for which K_W = 10^-14 at standard conditions (1 ATM and 25 ºC) (What exactly is the autoionization of water?)

Question 81

What two pieces of information are needed to calculate the pH of a weak acid?

Answer 81

The K_a of the acid and the acid concentration (using the ICEbox method). (]H⁺] = sqrt(K_a[HA]) (**somewhat confused on this**)

Question 82

What information is needed to predict the pH at the equivalence point of a titration?

Answer 82

The strengths of the acid and base being mixed. At the equivalence point, the pH = 7 if a strong acid is mixed with a strong base. It is \< 7 (less than 7) if a strong acid is mixed with a weak acid and \> 7 (greater than 7) if a strong base is mixed with a weak acid.

Question 83

Describe two ways to make a buffer:

Answer 83

1. Add roughly equal molar amounts of a weak acid and a salt of its conjugate base (or a weak base and the salt of its conjugate acid) 2. Neutralize half of a sample of a weak acid (or base) by a strong base (or acid)

Question 84

How is the PH of a buffered solution calculated?

Answer 84

Using the **Henderson-Hasselbalch Equation.** The *pH of a buffer is close to the pK_a of the weak acid used*, and the exact pH can be determined by taking the ratio of the conjugate base to acid into consideration.

Question 85

When does pH = pK_a for a buffer? What is this point called in titration?

Answer 85

When the concentrations of the weak acid and its conjugate base are equal (this occurs at the **half-equivalence point** in a titration experiment)

Question 86

How are the **common ion effect** and the **mechanism of a buffer** related?

Answer 86

They are the same thing, an application of **Le Chatelier's Principle**

Question 87

What is the enthalpy of formation?

Answer 87

The amount of energy associated with forming one mole of a compound from its constituent elements in their standard states

Question 88

What three things must be considered to determine whether a reaction will happen, or be spontaneous?

Answer 88

1. Change in Entropy 2. Change in Enthalpy 3. Change in termperature

Question 89

Describe the state of a reaction for which ΔG = 0

Answer 89

The reaction is at equilibrium

Question 90

What kind of reaction occurs at the **anode** of an **electrochemical cell**? At the **cathode**?

Answer 90

**Oxidation** occurs at the **anode** **Reduction** occurs at the **cathode**

Question 91

What is the sign of the cell voltage in an electrolytic cell?

Answer 91

Negative | (why?)

Question 92

What is the purpose of the **salt bridge** in a **galvanic cell**?

Answer 92

To prevent charge separation as electrons move from one chamber to the other. The salt bridge maintains charge neutrality in each chamber.

Question 93

What is the difference between an **electrolytic cell** and a **galvanic cell**?

Answer 93

(need to look up)

Question 94

What are the common labels for a curve of a redox titration?

Answer 94

The y-axis is normally E, electric potential in volts and the x-axis is normally the amount of titrant added in mL of solution.

Question 95

What informationis required to calculate the amount of an element that can be produced in an electrolytic cell?

Answer 95

The current (in Amps), the amount of time the current is applied, Faraday's constant, and the number of moles of electrons transferred per mole of the element formed (given by the half-reaction)