A catalyst will appear in the steps of a reaction mechanism, but it will not appear in the overall chemical reaction (as it is not a reactant or product).
Catalysts can either be in the same phase as the chemical reactants or in a distinct phase.
Search found 101 matches
- Thu Mar 11, 2021 11:38 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Catalyst
- Replies: 30
- Views: 1981
- Thu Mar 11, 2021 11:36 am
- Forum: Zero Order Reactions
- Topic: kind of reaction
- Replies: 25
- Views: 1091
Re: kind of reaction
Zero-order reactions are typically found when a material that is required for the reaction to proceed, such as a surface or a catalyst, is saturated by the reactants. A reaction is zero-order if concentration data is plotted versus time and the result is a straight line.
- Thu Mar 11, 2021 11:35 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts in the Slow Step
- Replies: 17
- Views: 867
Re: Catalysts in the Slow Step
A catalyst will not appear in the overall rate equation because it isn't chemically used up during a reaction.
- Thu Mar 11, 2021 11:34 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Units for Activation Energy
- Replies: 28
- Views: 1854
Re: Units for Activation Energy
J/mol or Kj/mol depending on the question.
- Thu Mar 11, 2021 11:33 am
- Forum: *Enzyme Kinetics
- Topic: Free Energy of Activation
- Replies: 5
- Views: 406
Re: Free Energy of Activation
Energy must be added to the reactants to overcome the energy barrier, which is recovered when products are formed. The energy barrier is Ea, the activation energy. The activation energy is different from the ΔG, which is the free energy difference between the reactants and products.
- Sun Mar 07, 2021 6:12 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: pH
- Replies: 17
- Views: 858
Re: pH
An acidic solution has far more positively charged hydrogen ions in it than an alkaline one, so it has greater potential to produce an electric current in a certain situation—in other words, it's a bit like a battery that can produce a greater voltage. A pH meter takes advantage of this and works li...
- Sun Mar 07, 2021 6:11 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration Cells at Equilibrium
- Replies: 7
- Views: 370
Re: Concentration Cells at Equilibrium
They are not always at equilibrium. But they work to reach equilibrium which is how a voltage is created.
- Sun Mar 07, 2021 6:09 pm
- Forum: Balancing Redox Reactions
- Topic: Resources for Redox Reactions
- Replies: 6
- Views: 417
Re: Resources for Redox Reactions
Have a look at Khan Academy I think they have some good videos explaining the concept thoroughly
- Sun Mar 07, 2021 6:07 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: nernst equation
- Replies: 20
- Views: 774
Re: nernst equation
It’s found after you balance the redox reactions :)
- Sat Mar 06, 2021 2:38 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Kinetic stability
- Replies: 14
- Views: 647
Re: Kinetic stability
Kinetic stability basically occurs when the reactants react really slowly. The slower the reaction occurs, the greater the kinetic stability. If you say, "This reaction is kinetically stable," then that implies that the reaction occurs very slowly.
- Thu Feb 25, 2021 3:19 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Types of Batteries
- Replies: 8
- Views: 524
Re: Types of Batteries
Rechargeable batteries rely on reversible reactions. Non rechargeable reactions do not
- Thu Feb 25, 2021 3:18 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: pH meter
- Replies: 11
- Views: 639
Re: pH meter
A pH meter is an instrument used to measure hydrogen ion activity in solutions - in other words, it measures acidity/alkalinity of a solution. The degree of hydrogen ion activity is ultimately expressed as pH level, which generally ranges from 1 to 14.
- Thu Feb 25, 2021 3:17 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Applications of the Nernst equation in Biology
- Replies: 4
- Views: 401
Re: Applications of the Nernst equation in Biology
In biochemistry, Nernst equation can be used to calculate the potential difference of ion between membranes. Hans H. Ussing, a Danish scientist, used a frog skin to measure the potential difference of sodium and potassium ions across the membranes with his famous invention, the Ussing chamber. This ...
- Thu Feb 25, 2021 3:16 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Ion selective Electrodes
- Replies: 2
- Views: 167
Re: Ion selective Electrodes
Yes you're right I believe !
- Thu Feb 25, 2021 3:15 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Cell
- Replies: 3
- Views: 205
Re: Cell
An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or using electrical energy to cause chemical reactions. The electrochemical cells which generate an electric current are called voltaic cells or galvanic cells and those that generate chemical ...
- Sun Feb 21, 2021 5:04 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: dilutions and Ecell
- Replies: 16
- Views: 3153
Re: dilutions and Ecell
I believe it should decrease the cell potential.
- Sun Feb 21, 2021 5:03 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Spontaneous Reduction
- Replies: 9
- Views: 512
Re: Spontaneous Reduction
For standard electrochemical cells: A redox reaction is spontaneous if the standard electrode potential for the redox reaction, Eo(redox reaction), is positive. If Eo(redox reaction) is positive, the reaction will proceed in the forward direction (spontaneous).
- Sun Feb 21, 2021 5:00 pm
- Forum: Balancing Redox Reactions
- Topic: Salt Bridge Diagram
- Replies: 8
- Views: 422
Re: Salt Bridge Diagram
Normally the anode is on the left and the cathode is on the right, but it really depends on the diagram, it could be either way :)
- Thu Feb 18, 2021 3:23 pm
- Forum: Balancing Redox Reactions
- Topic: Change in potential as i -> 0
- Replies: 12
- Views: 571
Re: Change in potential as i -> 0
It represents the current approaching zero
- Thu Feb 18, 2021 3:22 pm
- Forum: Balancing Redox Reactions
- Topic: Redox Mnemonic
- Replies: 11
- Views: 969
Re: Redox Mnemonic
OIL RIG is the one I used when I learnt high school chemistry. I personally think it’s the best one.
OIL - oxidation is loss of electrons
RIG - reduction is gain of electrons
OIL - oxidation is loss of electrons
RIG - reduction is gain of electrons
- Fri Feb 12, 2021 2:47 pm
- Forum: Van't Hoff Equation
- Topic: Chemistry analysis
- Replies: 5
- Views: 443
Re: Chemistry analysis
I really don't think there's a difference, maybe it's just a more specific name ?
- Fri Feb 12, 2021 2:46 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneous as Written
- Replies: 10
- Views: 501
Re: Spontaneous as Written
The negative value of ΔG° indicates that the reaction is spontaneous as written.
- Fri Feb 12, 2021 2:45 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Temperature for Gibbs Free Energy Calculations
- Replies: 6
- Views: 373
Re: Temperature for Gibbs Free Energy Calculations
Yes, temperature should always be in Kelvin :)
- Fri Feb 12, 2021 2:44 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: internal energy ideal gas
- Replies: 5
- Views: 313
Re: internal energy ideal gas
In Isothermal process the temperature is constant. The internal energy is a state function dependent on temperature. Therefore, the internal energy change is 0.
- Fri Feb 12, 2021 2:42 pm
- Forum: Phase Changes & Related Calculations
- Topic: Boiling water
- Replies: 25
- Views: 2796
Re: Boiling water
water has a high heat of vaporization, which is the amount of energy needed to change one gram of a liquid substance to a gas at constant temperature
- Fri Feb 12, 2021 11:29 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling #14
- Replies: 6
- Views: 244
Sapling #14
The delta H vap
of a certain compound is 15.85 kJ·mol−1
and its delta S vap
is 57.91 J·mol−1·K−1.
What is the boiling point of this compound?
I keep getting 0.7 degrees Celsius but it's saying it's wrong and I'm not entirely sure why.
of a certain compound is 15.85 kJ·mol−1
and its delta S vap
is 57.91 J·mol−1·K−1.
What is the boiling point of this compound?
I keep getting 0.7 degrees Celsius but it's saying it's wrong and I'm not entirely sure why.
- Sun Feb 07, 2021 6:33 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: reversible expansion
- Replies: 2
- Views: 137
Re: reversible expansion
For reversible processes (the most efficient processes possible), the net change in entropy in the universe (system + surroundings) is zero.
- Sun Feb 07, 2021 6:32 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Hc vs Hf
- Replies: 5
- Views: 2594
Re: Hc vs Hf
Hc is specifically enthalpy for combustion. Hf is the standard enthalpy formation in any circumstance basically
- Sun Feb 07, 2021 6:31 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Identification
- Replies: 8
- Views: 498
Re: Identification
The natural form of the elements are most stable - so diatomic molecules are an example
- Sun Feb 07, 2021 6:30 pm
- Forum: Calculating Work of Expansion
- Topic: q=-w
- Replies: 5
- Views: 175
Re: q=-w
This happens when the system experiences isothermal change(temp remains constant), thus delta U is zero. So, q=-w means that heat loss is equal work done on the system and visa versa is also true.
- Sun Feb 07, 2021 6:26 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Combustion = Exothermic
- Replies: 23
- Views: 792
Re: Combustion = Exothermic
It’s an oxidation reaction that releases heat. But relatively speaking, the energy released from forming bonds is larger than that of breaking bonds as well.
- Sun Jan 31, 2021 7:28 pm
- Forum: Phase Changes & Related Calculations
- Topic: Vapor vs gas
- Replies: 121
- Views: 8958
Re: Vapor vs gas
Vapor and gas are the same thing, so if in a question they say something has been vaporized, it has just turned from a liquid to a gas.
- Sun Jan 31, 2021 7:27 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: delta H vs delta U
- Replies: 11
- Views: 468
Re: delta H vs delta U
The difference between dH and dU becomes significant only when gases are involved (insignificant in solids and liquids)
dU is the total change in energy and dH is specific to the amount of work
dU is the total change in energy and dH is specific to the amount of work
- Sun Jan 31, 2021 7:25 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: "Bomb Calorimetry"
- Replies: 4
- Views: 243
Re: "Bomb Calorimetry"
A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Electrical energy is used to ignite the fuel; as it's burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the ca...
- Sun Jan 31, 2021 7:24 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat capacity vs Specific heat in Calorimetry
- Replies: 5
- Views: 187
Re: Heat capacity vs Specific heat in Calorimetry
Heat capacity is the ratio of the amount of heat energy transferred to an object to the resulting increase in its temperature.
Specific heat capacity is a measure of the amount of heat necessary to raise the temperature of one gram of a pure substance by one degree K.
Specific heat capacity is a measure of the amount of heat necessary to raise the temperature of one gram of a pure substance by one degree K.
- Thu Jan 28, 2021 4:50 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Increasing the yield
- Replies: 1
- Views: 76
Increasing the yield
In an example in the lecture, Dr Lavelle gave us the equation: N2(g)+3H2(g)-->2NH3(g) without adding more reactants how would you increase the yield of NH3? By removing some of the reactant. Surely by removing some of the reactant equilibrium will shift to the left to form more reactants then? I'm c...
- Sat Jan 23, 2021 10:28 am
- Forum: Ideal Gases
- Topic: Omitting solid/liquid
- Replies: 19
- Views: 692
Re: Omitting solid/liquid
we omit them from the equations because their concentrations do not change, therefore they are not involved in the equilibrium expression.
- Sat Jan 23, 2021 10:27 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: amphoteric vs amphiprotic
- Replies: 10
- Views: 268
Re: amphoteric vs amphiprotic
An amphiprotic substance is one which can both donate hydrogen ions (protons) and also accept them. Water is a good example.
The water acts as both an acid (donating hydrogen ions) and as a base (by accepting them).
Amphoteric means that they have reactions as both acids and bases.
The water acts as both an acid (donating hydrogen ions) and as a base (by accepting them).
Amphoteric means that they have reactions as both acids and bases.
- Sat Jan 23, 2021 10:26 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Polyprotic Acids
- Replies: 8
- Views: 308
Re: Polyprotic Acids
There is no specific cutoff, but as people said if the Ka2 is very small, then we can assume that all the ionization is from ka1 and not focus too much on it.
- Sat Jan 23, 2021 10:24 am
- Forum: Phase Changes & Related Calculations
- Topic: clarification
- Replies: 4
- Views: 209
Re: clarification
Heat and work are two different ways of transferring energy from one system to another. The distinction between heat and work is important in the field of thermodynamics. Heat is the transfer of thermal energy between systems, while work is the transfer of mechanical energy between two systems.Neith...
- Sat Jan 23, 2021 10:22 am
- Forum: Phase Changes & Related Calculations
- Topic: State Property
- Replies: 71
- Views: 2913
Re: State Property
It's a quality that is independent of how the substance was prepared.
As an example, the state of an electric battery requires the specification of the amount of electric charge it contains.
As an example, the state of an electric battery requires the specification of the amount of electric charge it contains.
- Sun Jan 17, 2021 6:22 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Acids, Bases, and Autoprotrolysis
- Replies: 7
- Views: 406
Re: Acids, Bases, and Autoprotrolysis
Yes, this is right.
Ka (acid disossication constant) * Kb (base dissociation constant) = Kw, which is for the constant for autoprotrolysis of water . (This is also equal to 1x10^-14)
Ka (acid disossication constant) * Kb (base dissociation constant) = Kw, which is for the constant for autoprotrolysis of water . (This is also equal to 1x10^-14)
- Sun Jan 17, 2021 6:19 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Pure Liquids (Solutes)
- Replies: 7
- Views: 303
Re: Pure Liquids (Solutes)
We don’t have to memorise the states of any compounds or elements. Pretty sure they will be given to us in the exam.
(S) solid
(L) liquid
(G) Gas
(Aq) Aqueous
(S) solid
(L) liquid
(G) Gas
(Aq) Aqueous
- Sun Jan 17, 2021 6:17 pm
- Forum: Ideal Gases
- Topic: R Value
- Replies: 17
- Views: 650
Re: R Value
The value will be on a constant sheet that he gives us for the exam! You won’t have to memorise it :)
- Sat Jan 16, 2021 8:33 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 2 question 10
- Replies: 2
- Views: 228
Sapling Week 2 question 10
Hi I'm having some trouble with this question:
N2O4 --->2NO2
I've calculated the equilibrium constant and the direction of the shift and the change in Kc. But I can't seem to work out the final part for the concentrations of NO2 and N2O4 after an extra 1mol.L-1 was added to the solution.
N2O4 --->2NO2
I've calculated the equilibrium constant and the direction of the shift and the change in Kc. But I can't seem to work out the final part for the concentrations of NO2 and N2O4 after an extra 1mol.L-1 was added to the solution.
- Tue Jan 12, 2021 1:05 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Approximation of X in cubic equations
- Replies: 5
- Views: 210
Approximation of X in cubic equations
In the example in at the beginning of Lecture 4, Dr. Lavelle said that since Kc is very small we can approximate that the concentrations of the compounds will stay roughly the same, and this is how we would calculate X to figure out the composition of the equilibrium mixture. Would Kc always be smal...
- Thu Jan 07, 2021 8:48 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: temperature change in reactions
- Replies: 11
- Views: 371
Re: temperature change in reactions
Increasing the temperature decreases the value of the equilibrium constant. Where the forward reaction is endothermic, increasing the temperature increases the value of the equilibrium constant.
- Thu Jan 07, 2021 8:45 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q and K
- Replies: 17
- Views: 723
Re: Q and K
K will always be the same.
Q would change if you added more products are reactants.
Q would change if you added more products are reactants.
- Thu Jan 07, 2021 8:44 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: H2O
- Replies: 44
- Views: 1898
Re: H2O
Like other compounds and elements, you do not include water if it is in solid or liquid phase in your expression. Only when H20 is in the gas phase will you be able to include it.
- Thu Jan 07, 2021 8:42 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q and K trend/similarity
- Replies: 8
- Views: 308
Re: Q and K trend/similarity
They basically follow the same trend. And as for sits and shifts, they both kinda mean the same thing. For example: equilibrium sits on the left. This would mean that the reverse reaction is favoured and products are converting back into reactants. If you say equilibrium shifts to the left, it still...
- Thu Jan 07, 2021 8:39 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: names for reaction quotient Q
- Replies: 19
- Views: 486
Re: names for reaction quotient Q
They all measure the reaction quotient but specifically, Qp measures partial pressure and Qc measures concentration. SO depending on what the question is asking for, you would substitute one into the equation.
- Fri Dec 11, 2020 6:13 pm
- Forum: Hybridization
- Topic: sp3 orbitals
- Replies: 6
- Views: 590
sp3 orbitals
So I know that sp3 hybridization corresponds to 4 regions of electron density. I just don't really understand how 2sp3 3sp3 works? How do you know which region to give what numbers to?
- Thu Dec 10, 2020 1:11 am
- Forum: Conjugate Acids & Bases
- Topic: Alkaline
- Replies: 16
- Views: 714
Re: Alkaline
Yes the mean the same thing. An alkaline solution is a basic solution, which has a pH>7.
- Thu Dec 10, 2020 1:10 am
- Forum: Conjugate Acids & Bases
- Topic: Neutralization
- Replies: 3
- Views: 239
Re: Neutralization
I honestly think either is fine. Also since I thin our exams are multiple choice, it will be fairly obvious whether they've written the products(salts) in ionic or compound form. I think Lavelle writes them as ions to show the separate cations and anions in the compound.
- Thu Dec 10, 2020 1:08 am
- Forum: Lewis Acids & Bases
- Topic: Lecture 28 #1
- Replies: 5
- Views: 225
Re: Lecture 28 #1
Bond strength is related to the length of the bond, and because Iodine has a much larger atomic radius than Fluorine, HI has a much longer, and therefore weaker, bond. The hydrogen is removed fairly easily, making HI a stronger acid
- Thu Dec 10, 2020 1:03 am
- Forum: Lewis Acids & Bases
- Topic: pH>pKa from Monday's lecture
- Replies: 2
- Views: 103
Re: pH>pKa from Monday's lecture
the pKa value is constant for each type of molecule. It is unaffected by concentration. Even a chemical considered a base can have a pKa value because the terms "acids" and "bases" simply refer to whether a species will give up protons (acid) or remove them (base). the main diffe...
- Fri Dec 04, 2020 11:48 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Relative Acidity and stability
- Replies: 4
- Views: 263
Re: Relative Acidity and stability
Anion stability is about the anion product of acid dissociation. If the anion is not stable, it will recombine with H+ and the reverse reaction dominates so there is less dissociation (higher pH). The more stable the anion, the more dissociation "remains" (less reverse reaction and so on).
- Thu Dec 03, 2020 12:52 am
- Forum: Biological Examples
- Topic: Co - VitB12
- Replies: 7
- Views: 442
Re: Co - VitB12
Cobalt is an essential element for humans, and is found at the centre of vitamin B12. Even though the body contains only 2–5 mg of vitamin B12, its involvement in the production of red blood cells means it is vital to life.
- Thu Dec 03, 2020 12:50 am
- Forum: Biological Examples
- Topic: chelates
- Replies: 8
- Views: 484
Re: chelates
A chelate is a compound containing a ligand (typically organic) bonded to a central metal atom at two or more points.
An example of a simple chelating agent is ethylenediamine
A single molecule of ethylenediamine can form two bonds to a transition-metal ion such as nickel(II), Ni2+.
An example of a simple chelating agent is ethylenediamine
A single molecule of ethylenediamine can form two bonds to a transition-metal ion such as nickel(II), Ni2+.
- Thu Dec 03, 2020 12:49 am
- Forum: Naming
- Topic: Oxidation State
- Replies: 16
- Views: 630
Re: Oxidation State
The oxidation state, commonly referred to as the oxidation number, describes the degree of oxidation (loss of electrons) of an atom in a chemical compound.
- Mon Nov 30, 2020 7:37 pm
- Forum: Student Social/Study Group
- Topic: Time differences with final exams
- Replies: 6
- Views: 334
Time differences with final exams
With students in different countries, is there a way for us to take our finals at a better time? I'm currently in Hong Kong and the final exam is scheduled for me from 3.30-6.30 am. please let me know. Thank you!
- Mon Nov 30, 2020 12:03 pm
- Forum: Naming
- Topic: Chlorido vs. chloro
- Replies: 11
- Views: 407
Re: Chlorido vs. chloro
both are accurate but most of the time chloro is used and is more common in textbooks etc. so I would just use chloro to make your life easier.
- Tue Nov 24, 2020 4:26 pm
- Forum: Hybridization
- Topic: Hybridization Clarification
- Replies: 9
- Views: 521
Re: Hybridization Clarification
In chemistry, orbital hybridization is the concept of mixing atomic orbitals into new hybrid orbitals (with different energies, shapes, etc., than the component atomic orbitals) suitable for the pairing of electrons to form chemical bonds in valence bond theory. Hybridization occurs when an atom bon...
- Tue Nov 24, 2020 4:23 pm
- Forum: Hybridization
- Topic: Lecture 23 question
- Replies: 5
- Views: 216
Re: Lecture 23 question
it's because the we are only concerned with the 2s and 2p orbitals in this example because we can assume that the 1s orbital is already filled when you look at nitrogen on the periodic table.
- Mon Nov 23, 2020 10:39 am
- Forum: Hybridization
- Topic: sp2 hybridization
- Replies: 3
- Views: 162
sp2 hybridization
So in Dr Lavelle's lecture, he said that the sp3 hybridization orbitals would have four because of the four regions of electron density. but for ethene, why is there sp2 hybridization with an additional 2p orbital, rather than just an sp3 hybridization? I didn't really get his explanation.
- Sun Nov 22, 2020 3:04 pm
- Forum: Hybridization
- Topic: Pi and Sigma Bonds
- Replies: 10
- Views: 378
Re: Pi and Sigma Bonds
Many covalent compounds contain multiple bonds (double or triple bonds). A difference between single and multiple bonds is that single bonds only have a sigma bond, whereas multiple bonds have both sigma and pi bonds.
- Wed Nov 18, 2020 7:52 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Shape generalities
- Replies: 4
- Views: 233
Re: Molecular Shape generalities
Yes, these rules will always be followed provided the structures have the right number of bonding electrons and lone pair electrons. so in the example you gave, any molecule with one lone pair of electrons and three bonding pairs of electrons will always be trigonal pyramidal, regardless of differen...
- Wed Nov 18, 2020 7:50 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Square Planar vs. Tetrahedral
- Replies: 7
- Views: 904
Re: Square Planar vs. Tetrahedral
In tetrahedral molecular geometry, a central atom is located at the center of four substituents, which form the corners of a tetrahedron. In square planar molecular geometry, a central atom is surrounded by constituent atoms, which form the corners of a square on the same plane . Example of tetrahed...
- Fri Nov 13, 2020 10:53 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: The shape
- Replies: 5
- Views: 318
The shape
does it matter which molecules you put on each wedge or in the plane? Let's say there was a molecule with different types of atoms, like PF3Cl2.
- Wed Nov 11, 2020 10:39 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Intermolecular Interactions' Strengths
- Replies: 3
- Views: 178
Re: Intermolecular Interactions' Strengths
they are all around the same strength, but as they said, the dipole-dipole intermolecular forces are permanent. induced dipole-induced-dipole are caused by correlations in the fluctuating polarizations of nearby particles, therefore they are constantly changing.
- Wed Nov 11, 2020 10:37 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: HCl4 and CCl4
- Replies: 1
- Views: 363
HCl4 and CCl4
In Lavelle's lecture, he gave the example of CCL4 and HCl4, I get that CCl4 is a bigger molecule. why does it have greater electron distortion? Is it just because cl has more e-? Also why would this mean that CCl4 has a much higher boiling point than methane?
- Tue Nov 10, 2020 9:40 am
- Forum: Bond Lengths & Energies
- Topic: Electron Pairs Interacting
- Replies: 3
- Views: 180
Re: Electron Pairs Interacting
Lone Pairs of electrons on neighboring atoms weaken the bond because of electron repulsion. Neighboring atoms in a molecule that have lone pair electrons will not be held together in their bond as tightly because the lone pair electrons of both atoms repel each another.
- Tue Nov 10, 2020 9:39 am
- Forum: Bond Lengths & Energies
- Topic: bond length for different compounds
- Replies: 3
- Views: 166
Re: bond length for different compounds
there are a number of factors affecting covalent bond strength: 1)Extent of atomic orbital overlap - Dependent on the size of the atom ,smaller atoms have better overlap of orbitals ,larger atoms tend to have more diffused orbitals, resulting in less effective overlap 2)Number of bonds between atoms...
- Tue Nov 10, 2020 9:32 am
- Forum: Bond Lengths & Energies
- Topic: Van der Waals
- Replies: 7
- Views: 447
Re: Van der Waals
Van der Waals forces include attraction and repulsions between atoms, molecules, and surfaces, as well as other intermolecular forces. Interactions between ions and molecules are ion-dipole interactions. Note that Van der Waals forces are induced dipole-dipole forces. These forces exist between all ...
- Fri Nov 06, 2020 10:52 am
- Forum: Coordinate Covalent Bonds
- Topic: H20 Example from Lecture today
- Replies: 4
- Views: 228
Re: H20 Example from Lecture today
In a water molecule, both O-H covalent bonds are of the 'normal' or 'conventional' type because each H atom contributes 1 electron to be shared between the two atoms. So no, it isn't a coordinate covalent bond.
- Wed Nov 04, 2020 10:57 am
- Forum: Octet Exceptions
- Topic: Boron
- Replies: 8
- Views: 461
Re: Boron
boron is in group 13, therefore it only has 3 valence electrons and can only form three bonds to have an FC=0.
- Wed Nov 04, 2020 10:55 am
- Forum: Octet Exceptions
- Topic: Reasoning for Octet Exception
- Replies: 19
- Views: 1151
Re: Reasoning for Octet Exception
reva_bajjuri wrote:do expanded octets usually correspond with resonance lewis structures or are those two things unrelated?
I'm pretty sure they're unrelated:)
- Wed Nov 04, 2020 10:53 am
- Forum: Octet Exceptions
- Topic: Radicals
- Replies: 5
- Views: 171
Re: Radicals
Free radicals are formed from molecules via the breakage of a chemical bond such that each fragment keeps one electron, also via redox reactions in the body. I'm not sure what specifically would happen if you were vitamin deficient, but oxidative stress can arise when cells cannot adequately destroy...
- Mon Nov 02, 2020 10:56 am
- Forum: Resonance Structures
- Topic: Delocalization of electrons
- Replies: 10
- Views: 442
Re: Delocalization of electrons
Resonant structures are simply, as Lavelle said in his lecture, when one Lewis structure has multiple bonds at equal locations. Delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond. This is in contrast to localized electr...
- Mon Nov 02, 2020 10:56 am
- Forum: Resonance Structures
- Topic: Delocalization of electrons
- Replies: 10
- Views: 442
Re: Delocalization of electrons
Resonant structures are simply, as Lavelle said in his lecture, when one Lewis structure has multiple bonds at equal locations. Delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond. This is in contrast to localized electr...
- Mon Nov 02, 2020 10:53 am
- Forum: Resonance Structures
- Topic: Resonance Hybrid
- Replies: 3
- Views: 114
Re: Resonance Hybrid
The simplest way to draw the nitrate ion I think would be either one of the three resonant structures. You can draw either of the 3 unless they ask you specifically to draw out all three. The reason why we can do this for benzene is because it is in a closed, hexagonal shape, therefore the circle in...
- Fri Oct 30, 2020 12:08 pm
- Forum: Trends in The Periodic Table
- Topic: Electron-electron repulsion
- Replies: 5
- Views: 275
Re: Electron-electron repulsion
When one or more of the groups is a lone pair of electrons (non-bonded electrons), the experimentally-observed geometry around an atom is slightly different than in the case where all groups are bonds. The actual bond angles are similar, but not exactly the same, as those predicted based on the tota...
- Fri Oct 30, 2020 12:04 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity
- Replies: 9
- Views: 419
Re: Electron Affinity
Electron affinity is the energy change that results from adding an electron to a gaseous atom. (EG) when a fluorine atom in the gaseous state gains an electron to form F⁻(g), the associated energy change is -328 kJ/mol. Unlike ionization energies, which are always positive for a neutral atom because...
- Wed Oct 28, 2020 12:25 pm
- Forum: Trends in The Periodic Table
- Topic: Elements with a low ionization energy
- Replies: 6
- Views: 515
Elements with a low ionization energy
why do elements with a low ionization energy form cations?
- Wed Oct 28, 2020 12:22 pm
- Forum: Trends in The Periodic Table
- Topic: Size of isoelectronic atoms/ions
- Replies: 9
- Views: 1290
Re: Size of isoelectronic atoms/ions
No, they would not be the same size due to their difference in nuclear charges. depending on the number of protons and neutrons in the nucleus, this determines the overall nuclear charge. and this means that the greater the nuclear charge, the smaller the atomic radii/ionic radii.
- Wed Oct 28, 2020 12:20 pm
- Forum: SI Units, Unit Conversions
- Topic: picometer conversion
- Replies: 13
- Views: 1767
Re: picometer conversion
1m = 1x10^12pm
- Sat Oct 24, 2020 3:44 pm
- Forum: Balancing Chemical Reactions
- Topic: Molar Mass
- Replies: 23
- Views: 1829
Re: Molar Mass
Yeah I think using the molar masses on the periodic table that he's given us for the midterm would be the most accurate. As for the sig figs, I think once you've calculated the answer, 3 sig figs will do. In your calculations, however, I would probably use the number exactly as it's given in the per...
- Sat Oct 24, 2020 3:41 pm
- Forum: Trends in The Periodic Table
- Topic: Nitrogen
- Replies: 7
- Views: 564
Re: Nitrogen
This happens because effective nuclear charge, which is a measure of what the net positive charge felt by the electrons is, increases. This implies that the atomic size of carbon will be a little bigger than that of nitrogen, which in turn will be a little bigger than that of oxygen
- Sat Oct 24, 2020 3:37 pm
- Forum: SI Units, Unit Conversions
- Topic: Midterm
- Replies: 26
- Views: 1086
Re: Midterm
I heard that there will be around 10-15 questions. All of them will be multiple choice. I also asked my TA about how partial credit is going to work. Some of the answers will be very similar, in the sense that, for example, A) is 100% correct and B) is 75% correct because you missed a calculation or...
- Thu Oct 22, 2020 1:29 pm
- Forum: *Shrodinger Equation
- Topic: Hamiltonian
- Replies: 3
- Views: 185
Hamiltonian
I've seen quite a few topics on the Schrodinger's equation and I understand what all the elements represent... apart from H(Hamiltonian). I have no idea as to what it does even after reading the textbook and watching Dr Lavelle's lecture. Anyone have any easy and straightforward explanations for it?
- Tue Oct 20, 2020 7:05 am
- Forum: DeBroglie Equation
- Topic: Measureable-wavelike properties
- Replies: 5
- Views: 227
Measureable-wavelike properties
Dr Lavelle mentioned in his worked example that a wavelength such as 1.64x10^-38 m is too small to be measured for wave-like properties.
what's the smallest detectable wavelength?
and also does this mean the object has only particle-like properties?
what's the smallest detectable wavelength?
and also does this mean the object has only particle-like properties?
- Tue Oct 20, 2020 7:02 am
- Forum: Properties of Light
- Topic: Difference between E=hv and E=hc/v?
- Replies: 9
- Views: 8473
Re: Difference between E=hv and E=hc/v?
E=h/v is the relationship showing the energy per photon, where the h represents Planck's constant (6.626x10^-34) and v represents the frequency. The equation E= hc/v does not exist, but I think you're referring to E= hc/ λ, which is the relationship between Planck's constant, the constant speed of l...
- Thu Oct 15, 2020 7:36 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Energy gap
- Replies: 4
- Views: 103
Energy gap
Dr Lavelle drew a diagram when he was explaining the energy levels in H-atoms. he said that all spectral lines showing up in the UV region involve the energy gap n=1 and n=2. Why is this? Is it because it has the highest energy difference?
- Thu Oct 15, 2020 6:35 am
- Forum: *Black Body Radiation
- Topic: What is Black Body?
- Replies: 53
- Views: 2239
Re: What is Black Body?
Dr Lavelle specifically said that black body radiation is more of a physics subject and that we won't need to know what it is or any detail about it for Chem14A.
- Thu Oct 15, 2020 6:33 am
- Forum: Significant Figures
- Topic: SI UNITS
- Replies: 12
- Views: 468
Re: SI UNITS
It really depends on the problem and if they specify It or not. When they do not specify, I just like to go with 3 sig figs because its the most standard way of rounding up figures and in the past I have been taught to do this by teachers
- Thu Oct 15, 2020 6:32 am
- Forum: Photoelectric Effect
- Topic: Photoelectric effect
- Replies: 9
- Views: 298
Re: Photoelectric effect
Increasing the frequency would result in the photon having more energy (E=hv). Increasing the intensity would result in an increase in the number of photons, but this has no change in their individual energy. No matter how bright the light is (or how many photons there are) none of the photons will...
- Wed Oct 14, 2020 11:00 am
- Forum: Photoelectric Effect
- Topic: Photoelectric effect
- Replies: 9
- Views: 298
Photoelectric effect
I just watched Dr Lavelle's lecture on the photoelectric effect and i was confused about the intensity of the light. so I know that changing the intensity of the light source doesn't change the energy per photon, but changing the frequency does. Does an increase in frequency mean a higher number of ...
- Fri Oct 09, 2020 9:47 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Avogadro's #
- Replies: 33
- Views: 3967
Re: Avogadro's #
Avogadro's number is 6.022×1023 molecules. With Avogadro's number, scientists can discuss and compare very large numbers, which is useful because substances in everyday quantities contain very large numbers of atoms and molecules. It is used in the equation number of moles = number of particles/avag...
- Fri Oct 09, 2020 9:43 am
- Forum: Student Social/Study Group
- Topic: Final Jitters
- Replies: 457
- Views: 334220
Re: Final Jitters
what I find most useful is when I relax a bit the night before. instead of cramming through the night you should try and get a good night of sleep. then in the morning, you should look through topics that you are the least confident in or compile some quick exam questions just to go through to boost...
- Tue Oct 06, 2020 5:10 am
- Forum: Administrative Questions and Class Announcements
- Topic: Periodic Table
- Replies: 3
- Views: 186
Periodic Table
Is there a copy of the official periodic table we should use that I could print off and have in my folder because I would find it much easier to use than the periodic table on the sapling learning website. If there is, where could I find it?