## Search found 103 matches

Sun Mar 15, 2020 7:50 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Extensive and Intensive Properties
Replies: 12
Views: 226

### Re: Extensive and Intensive Properties

extensive properties are dependent on the mass or amount of the substance, they are subject to change. Intensive properties, on the other hand, are independent of mass or amount and are constant for a given substance.
Sun Mar 15, 2020 7:47 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: platinum
Replies: 4
Views: 61

### Re: platinum

The side where there is no solid electrode has platinum.
Sun Mar 15, 2020 7:46 am
Forum: Second Order Reactions
Topic: 2nd order
Replies: 6
Views: 173

### Re: 2nd order

When two first-order reactants affect the rate constant or when one second-order reactant
Sun Mar 15, 2020 7:45 am
Forum: Ideal Gases
Topic: Kc vs Kp
Replies: 43
Views: 516

### Re: Kc vs Kp

Kc is used when you are given concentrations, and Kp is used when you are given partial pressures of gases. When Kp is given, the products and reactants are both gases. When Kc is given, the products and reactants can consist of gases or aqueous solutions
Sun Mar 15, 2020 7:43 am
Forum: Balancing Redox Reactions
Topic: cathode vs anode
Replies: 11
Views: 197

### Re: cathode vs anode

Cathode is where reduction occurs, and the anode is where oxidation occurs.
Mon Mar 09, 2020 11:39 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: k' vs kr
Replies: 13
Views: 122

### Re: k' vs kr

K’ is the rate of the reverse reaction. kr is the rate constant of the reaction
Mon Mar 09, 2020 11:29 am
Forum: General Rate Laws
Topic: Overall rate law
Replies: 8
Views: 102

### Re: Overall rate law

The slow step is considered the rate determining step. That means that the rate of the entire reaction is determined by that step. Imagine you are walking up a hill as a group, the slowest member of the group is the rate determining step
Mon Mar 09, 2020 11:27 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Instantaneous Rate
Replies: 13
Views: 159

### Re: Instantaneous Rate

The rate is very high when the reaction starts and decreases as the reaction continues. This can be determined by the slope of the tangent line at that point of the curve
Mon Mar 09, 2020 11:27 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating K
Replies: 6
Views: 57

### Re: Calculating K

K is a ratio of products to reactants. Ratios do not have units
Mon Mar 09, 2020 11:26 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow step
Replies: 7
Views: 62

### Re: Slow step

We could have either situation in an exam. The slow step will always be given to you
Sun Mar 01, 2020 10:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 12
Views: 112

### Re: Salt Bridge

If it wasn't a neutral salt, it would not allow for the charges to be balanced.
Sun Mar 01, 2020 10:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic and Voltaic Cells
Replies: 7
Views: 75

### Re: Galvanic and Voltaic Cells

Galvanic cells and voltaic cells are the same thing. They both generate electrical energy from chemical energy. Electrolytic cells are the opposite.
Sun Mar 01, 2020 10:36 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Reducing/oxidizing agent
Replies: 8
Views: 108

### Re: Reducing/oxidizing agent

The reducing agent will be the one with the more negative Eo values. the other one will be the oxidizing agent
Sun Mar 01, 2020 10:34 pm
Forum: Balancing Redox Reactions
Topic: Anode and Cathode
Replies: 9
Views: 94

### Re: Anode and Cathode

The anode is where there is a loss of electrons and the compound is oxidized. The cathode is where there is a gain of electrons and the compound is reduced. You can tell which is more likely by looking at the Eo values. the more negative one is a stronger reducing agent and is therefore more likely ...
Sun Mar 01, 2020 10:33 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: when to use K or Q
Replies: 18
Views: 234

### Re: when to use K or Q

K is when the reaction is at equilibrium. Q is at any other point in the reaction
Sun Mar 01, 2020 10:16 pm
Forum: Balancing Redox Reactions
Topic: Half reactions
Replies: 17
Views: 199

### Re: Half reactions

A half reaction is balanced when the number of electrons gained during reduction are equal to the number of electrons lost during oxidation
Sun Feb 23, 2020 9:05 pm
Forum: Balancing Redox Reactions
Topic: Half reactions
Replies: 17
Views: 199

### Re: Half reactions

Half reactions are balanced when there is no net gain or loss of electrons in the total reaction i.e. the number of electrons gained in reduction is equal to the number of electrons lost in oxidation.
Sun Feb 23, 2020 9:04 pm
Forum: Balancing Redox Reactions
Topic: Balancing in a Basic Solution
Replies: 3
Views: 36

### Re: Balancing in a Basic Solution

Basic solutions consist of a greater number of OH- ions, therefore, you need to balance the equation using OH- ions.
Sun Feb 23, 2020 9:02 pm
Forum: Ideal Gases
Topic: Conjugate acid and bases
Replies: 7
Views: 167

### Re: Conjugate acid and bases

A conjugate acid differs from its species by one H+ (ie it has one more H+ than the original species. A conjugate base, on the other hand, has one less proton than its original species.
Sun Feb 23, 2020 9:00 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: l vs ll
Replies: 5
Views: 35

### Re: l vs ll

A single line indicates direct contact/interaction between two states of matter/ substances. The double line, on the other hand, represents the salt bridge
Sun Feb 23, 2020 8:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram, what to include
Replies: 3
Views: 65

### Re: Cell Diagram, what to include

the order of a cell diagram is Anode(solid|gas| liquid )|| Cathode (liquid| gas| solid). the solid here is the electrode. if you are not told that any of the elements are solid, you assume the electrode to be an inert Pt electrode. If you follow this outline, you should have no problems with cell di...
Sun Feb 23, 2020 8:57 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Equations
Replies: 7
Views: 67

### Re: Balancing Redox Equations

It depends on the oxidation number of the element. If there is an increase in the oxidation number, oxidation is occurring. If there is a decrease in the oxidation number, reduction is occurring. Other, more obvious things to look out for include the gain or loss of protons and oxygen.
Mon Feb 17, 2020 12:13 am
Forum: Van't Hoff Equation
Topic: When to Use Vant Hoff
Replies: 5
Views: 74

### Re: When to Use Vant Hoff

You would use this when given equilibrium constants for two different temperatures and a standard change in enthalpy
Mon Feb 17, 2020 12:12 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Second law of thermodynamics
Replies: 6
Views: 136

### Re: Second law of thermodynamics

The second law of thermodynamics states that the total entropy of a system always increases for a favourable reaction. That is the system always moves to a state of increased disorder
Mon Feb 17, 2020 12:11 am
Forum: Balancing Redox Reactions
Topic: Rules for oxidation numbers
Replies: 6
Views: 37

### Re: Rules for oxidation numbers

This is because ions are charged particle formed as a result of the loss or gain of electrons that affect their oxidation number
Mon Feb 17, 2020 12:09 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: G vs G knot
Replies: 15
Views: 113

### Re: G vs G knot

G naught is explicitly for elements in their standard state.
Mon Feb 17, 2020 12:09 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ph
Replies: 8
Views: 92

### Re: Ph

It wouldn’t mention the term pH in that case. It would explicitly mention initial H+ ion concentration
Mon Feb 10, 2020 11:07 am
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: W
Replies: 4
Views: 34

### Re: W

W is degeneracy. It is equal to the number of states raised to the number of species
Mon Feb 10, 2020 11:06 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Exothermic reactions
Replies: 5
Views: 39

### Re: Exothermic reactions

Spontaneous processes have an increase in entropy. Delta H will be negative and S will be positive. Therefore G will be negative and hence the process is spontaneous
Mon Feb 10, 2020 11:04 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Is heat capacity/specific heat capacity a state function?
Replies: 2
Views: 30

### Re: Is heat capacity/specific heat capacity a state function?

Heat capacity is a state function as the method to attain the heat capacity of a system is the sum of each component part of the system
Mon Feb 10, 2020 11:03 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneity and Entropy
Replies: 3
Views: 40

### Re: Spontaneity and Entropy

An increase in entropy leads to a decrease in Gibbs free energy. Both these situations represent a spontaneous reaction
Mon Feb 10, 2020 11:02 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated vs Insulated
Replies: 3
Views: 67

### Re: Isolated vs Insulated

If a system is well insulated enough, it can be considered to be isolated ie there is no transfer of heat or energy
Mon Feb 03, 2020 1:07 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: closed vs isolated?
Replies: 7
Views: 83

### Re: closed vs isolated?

Closed systems are those that can exchange energy not matter with the surroundings. Isolated systems, on the other hand, can exchange neither with the surroundings. Examples of a closed system include a sealed container (that is capable of transmitting heat etc.), and examples of an isolated system ...
Mon Feb 03, 2020 1:05 am
Forum: Calculating Work of Expansion
Topic: Reversible
Replies: 7
Views: 63

### Re: Reversible

reversible means that even if there is an infinitesimal change in the system, there will be a significant change in the behavior of the system. the definitions of reversible in equilibrium reactions and thermodynamically, however, differ greatly.
Mon Feb 03, 2020 1:03 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: enthalpy
Replies: 7
Views: 50

### Re: enthalpy

Enthalpy is the total amount of heat within a system.
Mon Feb 03, 2020 1:02 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: taking phase change into account
Replies: 5
Views: 48

### Re: taking phase change into account

it is taken into account when energy is first required to change the state of matter and then heat the new phase. therefore for example the heating of water from ice takes into account the energy required to melt the ice and then raise the temperature of water.
Mon Feb 03, 2020 12:59 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Double bonds
Replies: 4
Views: 54

### Re: Double bonds

The conversion from a double bond to a single bond is a new bond being formed. for organic compounds for example it could be a C-H bond forming. the bond enthalpies of C=O and C-O + C-H are different.
Mon Feb 03, 2020 12:58 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Standard Reaction Enthalpy
Replies: 4
Views: 25

### Re: Standard Reaction Enthalpy

Enthalpy change of formation is the energy of reactants and products in their most stable state. Enthalpy change of reaction is the difference in those enthalpies
Sun Jan 26, 2020 9:53 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy is said to be additive
Replies: 10
Views: 108

### Re: Enthalpy is said to be additive

enthalpies of different reactions can be added together to get the total enthalpy of the system in its change from reactants to products
Sun Jan 26, 2020 9:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Weak acid/base
Replies: 14
Views: 158

### Re: Weak acid/base

if the Ka value is high, or the pKa value is low, the acid is generally a strong acid and vice versa for a weak acid. this is also true for Kb and bases
Sun Jan 26, 2020 9:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: hess's law
Replies: 5
Views: 38

### Re: hess's law

the total enthalpy of the system remains the same regardless of the route taken to reach the final product. this is important when the reaction from reactants to products in one step is energetically or chemically unfavorable
Sun Jan 26, 2020 9:48 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: removing H2 from N2 + 3H2 -> 2NH3
Replies: 7
Views: 130

### Re: removing H2 from N2 + 3H2 -> 2NH3

according to le chatelier's principle, a system works to minimize the effect of the change. therefore there will be an increase in the rate of the reverse reaction, and there will be H2 formed until it reached the required level
Wed Jan 22, 2020 10:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ice Box
Replies: 9
Views: 88

### Re: Ice Box

For an ICE box problem, the change would always be subtracted on the reactants side and added on the products side.
Mon Jan 13, 2020 11:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q
Replies: 10
Views: 108

### Re: Q

Q is the composition of a system at any time (even those other than equilibrium). It is an important indicator that tells you whether equilibrium lies in favor of products or reactants. when Q < K, the reaction will move toward the products, and if Q > K, the reaction will move towards the reactants...
Mon Jan 13, 2020 11:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw and H3O/OH concentrations
Replies: 5
Views: 47

### Re: Kw and H3O/OH concentrations

the Kw of water remains constant at a given temperature, although the concentrations of hydronium and hydroxide ions can vary. for example, in an acidic solution if [H3O+] is say 1.00 x 10^-2, then using the Kw, we can conclude that the [OH-] is 1.00 x 10^ -12.
Mon Jan 13, 2020 11:31 pm
Forum: Ideal Gases
Topic: When to use this equation
Replies: 14
Views: 157

### Re: When to use this equation

PV= nRT is used for ideal gases only. if concentrations and Kp are given, this equation can be used to calculate the partial pressure of products and reactants and vice versa, if partial pressures are given, concentrations can be calculated using this method
Mon Jan 13, 2020 11:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units for K
Replies: 21
Views: 211

### Re: Units for K

K does not have units as it is a constant value of the ratio of concentrations of products to reactants.
Mon Jan 13, 2020 11:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5J.5
Replies: 4
Views: 39

### Re: 5J.5

the H2 molecule has been omitted from the right side of the equation. if it were present, the number of molecules would be the same on the right and the left of the equation, therefore, there'd be no change in equilibrium as a result of a change in pressure.
Mon Jan 13, 2020 11:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6B.5d
Replies: 2
Views: 25

### Re: 6B.5d

find moles of OH- ions in 2ml of 0.175M KOH. Divide this value to obtain concentration of OH- ions. use the formula of pOH to calculate the pOH of solution and then subtract by 14 to calculate the pH
Mon Jan 13, 2020 11:24 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Effect of Inert Gases
Replies: 9
Views: 75

### Re: Effect of Inert Gases

Inert gases generally do not react, therefore, it is unlikely that their presence will change the reaction mixture at all.
Mon Jan 13, 2020 11:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentrations and the K value.
Replies: 7
Views: 71

### Re: Concentrations and the K value.

the stochiometric coefficients show the number of molecules of one type reacting together. therefore, if the equation is 2H20----> H3O+ + OH-, two water molecules react to give one H3O+ molecule and one OH- molecule. concentrations of products are multiplied and divided by reactants to the give the ...
Mon Jan 13, 2020 11:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6A21
Replies: 2
Views: 40

### Re: 6A21

The concentrations of H3O+ and OH- are equal in water. therefore, using the new value of Kw as 2.1x10^-14, square root it to get concentrations of H3O+ and OH-
Mon Jan 13, 2020 11:17 pm
Forum: Ideal Gases
Topic: ICE tables
Replies: 9
Views: 96

### Re: ICE tables

The ICE box is used for concentrations to calculate the concentration of reactants and products at equilibrium given a Kc value. If there is a Kp value given, then pressure in the units atm will be used.
Mon Dec 09, 2019 12:06 am
Forum: Naming
Topic: -ate
Replies: 10
Views: 231

### Re: -ate

The -ate is only added for a negatively charged ion. For neutral and positively charged ion, just the metal name is required
Mon Dec 09, 2019 12:06 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Nitro vs Nitrito
Replies: 6
Views: 177

### Re: Nitro vs Nitrito

NO2- is nitro and ONO is nitrito
Mon Dec 09, 2019 12:04 am
Forum: Student Social/Study Group
Topic: most stable
Replies: 6
Views: 226

### Re: most stable

It means a formal charge of 0 on most atoms.
Mon Dec 09, 2019 12:04 am
Forum: *Titrations & Titration Calculations
Topic: Types of Titrations
Replies: 2
Views: 130

### Re: Types of Titrations

Acid-Base titrations are the only ones that we need to know as of now. Other examples are red-ox titration
Mon Dec 09, 2019 12:03 am
Forum: Hybridization
Topic: Identifying Hybrid Orbitals
Replies: 5
Views: 142

### Re: Identifying Hybrid Orbitals

To find a hybrid orbital, look at the number of regions of electron density around the atom. If there are 2, the hybridisation will be sp, if there are 3, sp2, 4 = sp3, 5= sp3d, 6=sp3d2
Sun Dec 01, 2019 5:15 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: structure of water
Replies: 4
Views: 41

### Re: structure of water

This is because of the orientation of the lone pairs of electrons in water. Only one can have the correct orientation to bond.
Sun Dec 01, 2019 5:13 pm
Forum: Hybridization
Topic: 2F.3
Replies: 3
Views: 37

### Re: 2F.3

This is because the formal charge of the second structure is lower due to the presence of resonant structures.
Sun Dec 01, 2019 5:11 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: HW 9C.7
Replies: 1
Views: 34

### Re: HW 9C.7

Something can be a chelating compound when it forms a ring with the metal being a part of it. The answer to your question is the one where the NH3's are closest to each other.
Sun Dec 01, 2019 5:08 pm
Forum: Lewis Acids & Bases
Topic: BF3
Replies: 2
Views: 31

### Re: BF3

BF3 is a lewis acid because it is electron deficient and has empty orbitals. Therefore it is an electron acceptor.
Sun Dec 01, 2019 5:07 pm
Forum: Lewis Acids & Bases
Topic: strong and weak acids
Replies: 3
Views: 51

### Re: strong and weak acids

You should know at least some common acids such as hydrochloric acid, sulphuric acid as strong acids, and acetic acid as a weak acid. You should be alright if you're familiar with the examples he went over in lecture. You can tell a base is a strong base if it dissociates completely in solution to f...
Sun Nov 24, 2019 1:08 pm
Forum: Hybridization
Topic: Concept
Replies: 3
Views: 51

### Re: Concept

For hybridization, you are just mixing orbitals, to form new orbitals with different shape, size and energy than the component orbitals. This is energetically favorable for the formation of bonds and therefore explains why atoms such as carbon form 4 covalent bonds.
Sun Nov 24, 2019 1:05 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Bronsted vs. Lewis Acids
Replies: 9
Views: 108

### Re: Bronsted vs. Lewis Acids

The definition of an acid varies in both cases. Bronsted focuses on protons. A Bronsted acid is therefore a proton donor. However, Lewis focuses on electrons, and a lewis acid is an electron acceptor.
Sun Nov 24, 2019 1:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle of bent
Replies: 17
Views: 242

### Re: Bond Angle of bent

This depends on whether the atom has one or two lone pairs, in addition to its two bond pairs. If it has one lone pair, the bond angle will be < 120 degrees, however, if it has two lone pairs, it will have a bond angle << 109.5 degrees (ex. Water has a bond angle of approx. 104.5 degrees)
Sun Nov 24, 2019 1:00 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Charges
Replies: 4
Views: 75

### Re: Charges

No, you can look at the position of the atom on the periodic table and see how many electrons it needs to gain or lose to attain the electronic configuration of the closest noble gas. You will need to make sure that this is energetically favorable. Ex. A sodium atom would rather lose one electron th...
Sun Nov 24, 2019 12:57 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Compound
Replies: 3
Views: 58

### Re: Coordination Compound

A coordination compound is one that contains a coordination complex within it. It is when the anions are bonded to the metal via coordinate covalent bonds,where both electrons are donated via the metal atom.
Sun Nov 17, 2019 2:22 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Van Der Waals Interaction
Replies: 11
Views: 107

### Re: Van Der Waals Interaction

Yes, all molecules regardless of their polarity or non-polarity experience Van Der Waals interactions due to shift in the electron cloud density. The order of interaction from strongest to weakest is ion-dipole, dipole-dipole, dipole-induced dipole, induced dipole-induced dipole.
Sun Nov 17, 2019 2:20 am
Forum: Determining Molecular Shape (VSEPR)
Topic: London dispersion forces and vander waals
Replies: 5
Views: 121

### Re: London dispersion forces and vander waals

An example for a Van der Waals interaction would be between N2 molecules. They do not have an inherent dipole moment beween the two atoms as they are identical, however, there is an instantaneous dipole created due to a shift in the electron density distribution, which thereby induces a dipole momen...
Sun Nov 17, 2019 2:15 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles with Different Atoms
Replies: 4
Views: 81

### Re: Bond Angles with Different Atoms

CCl4 is a non-polar molecule as the dipole moments of each of the C-Cl bonds cancel each other out, as they are in exactly opposite directions. However, for the molecule CCl3F, there will be a dipole moment generated in the direction of the fluorine atom, due to its high electronegativity. Bond angl...
Sun Nov 17, 2019 2:10 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Formula
Replies: 7
Views: 69

### Re: VSEPR Formula

Although while naming the molecule, the lone pairs of electrons do not matter, they do influence the molecular geometry of the molecule, and thus change bond angles due to their presence or absence. Each lone pair of electrons represents one region of electron density.
Sun Nov 17, 2019 2:07 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Large Molecules
Replies: 2
Views: 26

### Re: Large Molecules

We can consider any of the carbon atoms to be the central atom in this case, and look at the regions of electron density around each one individually. This will also determine the bond angles in each part of the hydrocarbon.
Sun Nov 10, 2019 12:47 am
Forum: Bond Lengths & Energies
Topic: Shape of Molecules and bond strength
Replies: 5
Views: 55

### Re: Shape of Molecules and bond strength

The shape of the molecule determines the bond strength as a more branched structure (such as 2,2- dimethylpropane) have smaller surface areas. As the intermolecular attractive forces are determined by this, the forces as stronger. Whereas for straight molecules, it is the opposite.
Sun Nov 10, 2019 12:41 am
Forum: Bond Lengths & Energies
Topic: negative Ep
Replies: 5
Views: 83

### Re: negative Ep

This is because the charges on both the atoms are different i.e. one is positive and the other is negative. When using the equation to calculate Ep, you are multiplying both the charges on the atoms (q1.q2/r^2). Since multiplying a negative by a positive, will always give you a negative answer, Ep i...
Sun Nov 10, 2019 12:35 am
Forum: Dipole Moments
Topic: Van Der Waals
Replies: 5
Views: 87

### Re: Van Der Waals

All molecules generally possess Van Der Waals forces due to the varying electron density distribution that occurs as a result of the electron cloud moving which temporarily creates a dipole, which can then induce other surrounding molecules to form dipole moments in them.
Sun Nov 10, 2019 12:32 am
Forum: Dipole Moments
Topic: Limits to Hydrogen Bonds
Replies: 1
Views: 37

### Re: Limits to Hydrogen Bonds

This is due to the high electronegativity of the elements N, O and F. This results in a partial negative charge that attracts hydrogen which has a partial positive charge. It is also due to the lone pairs of electrons present around these atoms in a covalent bond.
Sun Nov 10, 2019 12:28 am
Forum: Ionic & Covalent Bonds
Topic: covalent relationship to polarizability
Replies: 4
Views: 55

### Re: covalent relationship to polarizability

High polarizability and high polarizing power are when the electrons in an ionic bond can be distorted. This distortion is a result of the positively charged cation attracting negatively charged electrons. As this resembles the shared characteristic that electrons in a covalent bond face, it is cons...
Sun Nov 03, 2019 12:13 am
Forum: Lewis Structures
Topic: Lewis Structures
Replies: 9
Views: 90

### Re: Lewis Structures

The one with the lowest energy will always be correct so it safer to draw that and all it’s resonant structures.
Sun Nov 03, 2019 12:11 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 4pi?
Replies: 2
Views: 74

### Re: 4pi?

This is because the actual equation of h bar divided by 2. However h bar has a value of h/2 pi, therefore giving you h/4 pi
Sun Nov 03, 2019 12:09 am
Forum: Ionic & Covalent Bonds
Topic: Bond Strength
Replies: 3
Views: 40

### Re: Bond Strength

It is because of the size of the fluoride and chloride ion too. The fluoride ion is smaller than the chloride ion as size of an ion increases down a group. Therefore, the electrons are held more closely and hence, the bond is stronger.
Sun Nov 03, 2019 12:07 am
Forum: Electronegativity
Topic: What is isoelectronic?
Replies: 13
Views: 117

### Re: What is isoelectronic?

Isoelectronic means atoms or ions that have the same number of electrons. An example of this would be Na+, Mg2+
Sun Nov 03, 2019 12:04 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Loss from 4s over 3d?
Replies: 4
Views: 51

### Re: Loss from 4s over 3d?

After the 3D orbital is filled, it falls to a lower energy than the 4s orbital. Therefore, since electrons are first lost from the highest energy shell or valence shell first, the 4s orbital loses electrons before the 3D orbital.
Sun Oct 27, 2019 3:35 pm
Forum: Ionic & Covalent Bonds
Topic: Double and single bond lengths
Replies: 6
Views: 57

### Re: Double and single bond lengths

The double bond consists of two types of bonds, the pi bond and the sigma bond. The sigma bond is stronger than the pi bond which results in a shorter bond length. As for a triple bond, there are two pi bonds and one sigma bond, which results in an even shorter bond length.
Sun Oct 27, 2019 3:30 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Expanded Valence Shells
Replies: 1
Views: 51

### Re: Expanded Valence Shells

For Chemistry 14A, those are the only elements we need to know follow the expanded octet rule. However, any element in Period 3 or later can generally experience an expanded octet due to the presence of the additional d and f subshells that get filled at higher energy levels.
Sun Oct 27, 2019 3:15 pm
Forum: Ionic & Covalent Bonds
Topic: Benzene's covalent bond
Replies: 2
Views: 42

### Re: Benzene's covalent bond

Benzene has two possible resonant structures, with alternating double and single covalent bonds between Carbon atoms. On account of this variability in the density of the electron cloud, there is known to be a stable cloud of electrons on either side of the benzene molecule. Thus, this provides grea...
Sun Oct 27, 2019 3:12 pm
Forum: Trends in The Periodic Table
Topic: 1F.3
Replies: 3
Views: 68

### Re: 1F.3

You have to know that a higher negative charge means that there are more electrons added to the atom to achieve stability. There is greater electron-electron repulsion when electrons are added to the valence shell. As you move left to right across the periodic table, the atomic radius decreases. By ...
Sun Oct 27, 2019 3:06 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 8
Views: 73

### Re: Resonance

Resonant structures show all the possible orientations the electrons can take within a molecule. All resonant structures are virtually the same. They exist only because of the electron density shifting.
Sat Oct 19, 2019 4:27 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Cr and Cu
Replies: 5
Views: 60

### Re: Cr and Cu

Cu and Cr do not follow the traditional Aufbau principle as half or fully filled d-orbitals are at a higher energy than s orbitals. This is done to reduce electron-electron repulsion within the orbital.
Sat Oct 19, 2019 4:24 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Outer electrons
Replies: 2
Views: 44

### Re: Outer electrons

Yes, this is due to electron shielding. Electron shielding results in a lower effective nuclear charge on the valence electrons and thus explains why valence electrons take part in chemical reactions.
Sat Oct 19, 2019 4:18 pm
Forum: Properties of Electrons
Topic: Photo and electron energy
Replies: 4
Views: 51

### Re: Photo and electron energy

The electron will only absorb energy equal to the energy difference between two energy levels. Therefore if the energy is greater than the energy difference, the photon will not be absorbed unless the excess energy can be released in another way (eg. lattice vibration). However, assuming this is not...
Sat Oct 19, 2019 4:11 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Aufbau
Replies: 3
Views: 40

### Re: Aufbau

The Aufbau Principle states that the orbitals with the lower energy level get filled with electrons before the higher energy level. Thus, this gives us information about the electronic configuration of the atom.
Sat Oct 19, 2019 4:08 pm
Forum: Quantum Numbers and The H-Atom
Topic: Correlation Between n and l
Replies: 6
Views: 87

### Re: Correlation Between n and l

l indicates the azimuthal quantum number of an element that denotes the subshells the element contains;
l=0 signifies the s orbital (with a possible value of 0)
l=2 signifies the p orbital (with possible values of -1,0,1)
l=3 signifies the d orbital ( with possible values of -2, -1, 0, 1, 2)
Sat Oct 12, 2019 10:22 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Post Module Assessment: Experiment names
Replies: 2
Views: 83

### Re: Post Module Assessment: Experiment names

The answer for #13 would be C. Atomic absorption spectroscopy; Absorption line spectrum, as this question asks about absorption, and the process of finding the spectrum of the compound out is called Atomic absorption spectroscopy, and this produces an Absorption line spectrum. The answer for #14 wou...
Sat Oct 12, 2019 10:18 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Video Module
Replies: 1
Views: 53

### Re: Atomic Spectra Video Module

In 1m there are 1650763.73 wavelengths of krypton-86. There by dividing 1m by 1650762.72 wavelengths, the wavelength of each wave can be calculated to be 605.8nm. Thus, this falls under the visible spectrum. The energy can then be calculated by using the equation c=\nu \lambda , followed by the equa...
Sat Oct 12, 2019 10:11 pm
Forum: DeBroglie Equation
Topic: De Broglie Equation
Replies: 2
Views: 22

### Re: De Broglie Equation

The De Broglie cannot be used for light as light or photons are considered to massless, and thus any answer that you would get from that equation would be zero. The De Broglie equation can only be used for objects with a small mass and high frequency.
Sat Oct 12, 2019 10:05 pm
Forum: Properties of Light
Topic: Question on 1A 11
Replies: 4
Views: 44

### Re: Question on 1A 11

The Balmer and Lyman series are series defined by the final position of the electron, after a photon is emitted. The Lyman series involve jumps to or from the ground state (n=1); the Balmer series (in which all the lines are in the visible region) corresponds to n=2.
Sat Oct 12, 2019 10:02 pm
Forum: Photoelectric Effect
Topic: Removing electrons in Photoelectric concept
Replies: 2
Views: 24

### Re: Removing electrons in Photoelectric concept

The threshold energy required to remove an electron from the metal surface varies from metal to metal. Each metal has a different threshold energy. To remove an electron from the metal surface, the energy of the photon hitting the metal surface has to be exactly equal to the difference of energy bet...
Wed Oct 02, 2019 10:08 pm
Forum: Significant Figures
Topic: When to apply sig figs?
Replies: 4
Views: 78

### Re: When to apply sig figs?

No; you should only round your answer to the proper amount of significant figures at the end of the problem. You should never round off your intermediary calculations.
Wed Oct 02, 2019 10:02 pm
Forum: Empirical & Molecular Formulas
Topic: 5 Homework Problems Due
Replies: 21
Views: 323

### Re: 5 Homework Problems Due

You only have to do five problems out of the ones that Professor Lavelle selected, but my TA said it is highly beneficial to do most or even all the selected problems. I think about 1/8 problems on the tests are based off of the concepts from the homework.

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