Search found 100 matches
- Sun Mar 15, 2020 9:30 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Glass Electrode
- Replies: 5
- Views: 417
Re: Glass Electrode
Glass electrodes are used to measure pH and Ecell measurements are converted to [H+] concentrations.
- Sun Mar 15, 2020 9:18 pm
- Forum: General Rate Laws
- Topic: Overall Order
- Replies: 6
- Views: 437
Re: Overall Order
The overall order is equal to all the exponents on the reactant concentrations added together.
- Sun Mar 15, 2020 9:06 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Seeing how many electrons transfer
- Replies: 3
- Views: 324
Re: Seeing how many electrons transfer
Both ways do work, but the easier method is generally to split up the half reactions and balance it that way depending on whether it is a basic or acidic solution.
- Sun Mar 15, 2020 9:05 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Doing work vs work done
- Replies: 8
- Views: 693
Re: Doing work vs work done
Work is positive when it is being done on the system (eg. compression) while work is negative the system is doing work on the system (eg expansion).
- Sun Mar 15, 2020 9:00 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: catalyst
- Replies: 4
- Views: 367
Re: catalyst
catalysts are used up and then reformed so they start in the reactants of one reaction and are reformed in the products of another reaction.
- Sun Mar 08, 2020 11:42 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: K’
- Replies: 4
- Views: 382
Re: K’
k' is the rate constant of the reverse reaction. So at equilibrium, k[A][B]=k'[C][D]
- Sun Mar 08, 2020 11:35 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: galvanic vs electrolytic
- Replies: 12
- Views: 925
Re: galvanic vs electrolytic
A galvanic cell have a positive standard Ecell while an electrolytic cell have a negative standard Ecell and it is not spontaneous.
- Sun Mar 08, 2020 11:08 pm
- Forum: General Rate Laws
- Topic: General Rate Laws
- Replies: 7
- Views: 567
Re: General Rate Laws
In the beginning of a reaction, there are no products present so we use the initial concentrations of the reactants because only the forward reaction occurs.
- Sun Mar 08, 2020 11:03 pm
- Forum: General Rate Laws
- Topic: Changing the mass of electrodes
- Replies: 6
- Views: 400
Re: Changing the mass of electrodes
Changing the mass would not affect the Ecell because in the Nernst equation, which is used to calculate the Ecell, the mass is not incorporated into the equation.
- Sun Mar 01, 2020 11:10 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: units
- Replies: 11
- Views: 787
Re: units
The units for the rate of a reaction are moles per liter per unit of time.
- Sun Mar 01, 2020 11:06 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell notation
- Replies: 2
- Views: 237
Re: Cell notation
The pt(s) is an inert metal inserted as an electrode because the other elements are not solids, so it should not be included in the balanced equation. The other elements in the cell diagram should be included in the balanced equation.
- Sun Mar 01, 2020 9:26 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: first order
- Replies: 8
- Views: 656
Re: first order
The graph of ln(reactant) and time is a straight line and the slope is linear.
- Sun Mar 01, 2020 9:22 pm
- Forum: Balancing Redox Reactions
- Topic: Cell Diagrams
- Replies: 14
- Views: 1006
Re: Cell Diagrams
The cell diagram is written as the anode (oxidation reaction) first on the left side followed by the cathode (reduction reaction) similar to how a cell would be drawn.
- Sun Feb 23, 2020 9:03 pm
- Forum: Balancing Redox Reactions
- Topic: Half reactions
- Replies: 17
- Views: 943
Re: Half reactions
The half reactions are balanced when they have an equal number of e- charges on the reactant and product sides.
- Sun Feb 23, 2020 8:54 pm
- Forum: Ideal Gases
- Topic: Conjugate acid and bases
- Replies: 7
- Views: 582
Re: Conjugate acid and bases
A conjugate acid is the acid when it loses its H+ ion, so it should have a one less charge than the acid. A conjugate base is the base when it gains an H+ ion, so it should have one more charge than the base.
- Sun Feb 23, 2020 8:52 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing in a Basic Solution
- Replies: 3
- Views: 223
Re: Balancing in a Basic Solution
A basic solution contains less H+ ions, so more OH- ions, so a basic solution should be balanced with the OH- ions.
- Sun Feb 23, 2020 8:50 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Equation
- Replies: 7
- Views: 557
Re: Van't Hoff Equation
The Van't Hoff equation is used to calculate K (equilibrium constant) at different temperatures if the change in enthalpy is known.
- Sun Feb 23, 2020 8:46 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gp=Gr
- Replies: 3
- Views: 398
Re: Gp=Gr
At equilibrium, the forward and reverse reactions occur at the same right which means that they are at their lowest energy states. As a result, the Gibbs free energy of the reactants and products has to be the same at equilibrium.
- Sun Feb 16, 2020 9:52 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibb's Free Energy
- Replies: 7
- Views: 385
Re: Gibb's Free Energy
Gibbs Free Energy is the amount of free energy available to do work. It is a state function, so only the initial and final amounts matter.
- Sun Feb 16, 2020 9:46 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isochoric
- Replies: 8
- Views: 622
Re: Isochoric
iso means same and choric means volume, so isochoric means constant volume.
- Sun Feb 16, 2020 9:33 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Delta S
- Replies: 8
- Views: 679
Re: Delta S
Delta S is the entropy of the system. Delta S surroundings is the entropy of the surroundings. Delta S total is the entropy of the surroundings and system combined.
- Sun Feb 16, 2020 9:31 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated versus closed
- Replies: 7
- Views: 628
Re: Isolated versus closed
An isolated system, like combustion in a bomb calorimeter, is when nothing changes with the surroundings. A closed system, like a sealed beaker, is when only energy can exchange with the surroundings.
- Sun Feb 16, 2020 9:28 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Work
- Replies: 14
- Views: 1039
Re: Work
when something is being compressed, work is done by the system, so it is positive. When something is expanding, work is done on a system, so it is negative.
- Sun Feb 09, 2020 9:02 pm
- Forum: Ideal Gases
- Topic: Change in pressure
- Replies: 7
- Views: 525
Re: Change in pressure
Increasing the pressure will shift the reaction to the side with fewer moles of gas and decreasing the pressure will shift the reaction to the side with more moles of gas. If there is an equal number of moles on the reactants and products, then there will be no change.
- Sun Feb 09, 2020 8:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Le Chatelier's Principle
- Replies: 5
- Views: 305
Re: Le Chatelier's Principle
When you are expanding a gaseous mixture, you are increasing the volume, so decreasing the pressure, so the reaction would proceed to the side with more moles of gas.
- Sun Feb 09, 2020 8:56 pm
- 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: 4G1
- Replies: 1
- Views: 96
Re: 4G1
The formula for calculating W is (# of microstates)^#atoms/molecules. So for part a, if the nano structure is aligned in the same direction, the number of microstates is 1 and the number of molecules is 64, so W would be 1^64 which is one. For part b, the number of microstates is 4 and the number of...
- Sun Feb 09, 2020 8:53 pm
- Forum: Calculating Work of Expansion
- Topic: 4A.3
- Replies: 4
- Views: 208
Re: 4A.3
Because work is equal to -p delta V, to find the volume of the pump, you need to use the formula for calculating the volume of a cylinder which is pi (r)^2 X height, with the height being -20 because the pump is being compressed. Using the volume and the given pressure, you can plug the values into ...
- Sun Feb 09, 2020 8:50 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: 4G.1
- Replies: 3
- Views: 268
Re: 4G.1
If they are all aligned in the same direction, then the microstate would be one.
- Sun Feb 02, 2020 11:29 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: delta U
- Replies: 9
- Views: 447
Re: delta U
Change in internal energy is equal to q(heat)+w(work).
- Sun Feb 02, 2020 11:22 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Types of Systems
- Replies: 7
- Views: 460
Re: Types of Systems
In a closed system, energy can exchange with the surroundings. An example is a sealed beaker of water.
- Sun Feb 02, 2020 8:53 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature
- Replies: 14
- Views: 593
Re: Temperature
A negative delta H is exothermic because energy is released.
- Sun Feb 02, 2020 8:50 pm
- Forum: Calculating Work of Expansion
- Topic: Expansion
- Replies: 4
- Views: 147
Re: Expansion
work of expansion will be a negative value because the change in volume is positive, while work of compression will be a positive value because the change in volume is negative.
- Sun Feb 02, 2020 8:46 pm
- Forum: Ideal Gases
- Topic: PV=nRT
- Replies: 74
- Views: 5162
Re: PV=nRT
P is pressure in atm, V is volume in liters, n is the number of moles, R is the gas constant 8.206 x 10-2 L·atm·K-1·mol-1, and T is the temperature in Kelvin.
- Sun Jan 26, 2020 9:29 pm
- Forum: Ideal Gases
- Topic: Determining N
- Replies: 9
- Views: 430
Re: Determining N
Only moles of gas are accounted for because it is the ideal gas law.
- Sun Jan 26, 2020 9:28 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy is said to be additive
- Replies: 10
- Views: 354
Re: Enthalpy is said to be additive
Because enthalpies of different reactions can be added together, it is said to be additive.
- Sun Jan 26, 2020 9:14 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy Calculations
- Replies: 5
- Views: 151
Re: Enthalpy Calculations
I think you should just know that the enthalpy is positive for all the phase changes.
- Sun Jan 26, 2020 9:13 pm
- Forum: Calculating Work of Expansion
- Topic: Work Units
- Replies: 3
- Views: 131
Re: Work Units
Since work is the energy required to do something, it is measured in joules.
- Sun Jan 26, 2020 9:04 pm
- Forum: Phase Changes & Related Calculations
- Topic: enthalpy of phase changes
- Replies: 8
- Views: 270
Re: enthalpy of phase changes
No because it requires heat energy to go from a solid to a liquid to vapor so the reactions would be endothermic.
- Sun Jan 26, 2020 9:01 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Exothermic and Endothermic
- Replies: 11
- Views: 780
Re: Exothermic and Endothermic
Because an exothermic reaction releases energy and the energy of the products is lower than the energy of the reactants, the enthalpy is negative. An endothermic reaction absorbs energy so the energy of the products is higher than the energy of the reactants, so the enthalpy is positive.
- Sun Jan 19, 2020 11:53 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: H20 in the ICE table
- Replies: 26
- Views: 1541
Re: H20 in the ICE table
Yes, you should leave out H2O because we assume that it is in excess so the concentration doesn't affect the reaction.
- Sun Jan 19, 2020 11:48 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kw
- Replies: 2
- Views: 136
Re: Kw
The Kw value is a constant value of 1.0 X 10^-14 and it is used to either find the concentration of [OH-] or [H3O+] if either of the concentrations of the acid or base are given.
- Sun Jan 19, 2020 1:49 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Endothermic vs. exothermic
- Replies: 5
- Views: 243
Re: Endothermic vs. exothermic
When the temperature increases and the reaction is endothermic, the amount of reactants increases, so to balance out to equilibrium, the reaction will shift towards the products.
- Sun Jan 19, 2020 1:47 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure
- Replies: 5
- Views: 243
Re: Pressure
An increase in pressure will favor the side of the reaction with less moles of gas and an decrease in pressure will favor the side of the reaction with more moles of gas. However, if an inert gas is added to the system, there is no change in the reaction.
- Sun Jan 19, 2020 1:38 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Quadratic Equation
- Replies: 8
- Views: 393
Re: Quadratic Equation
When doing an ICE table, solving for x requires using a quadratic equation. However, if the K value given is less than 10^-3, then we can assume that the x value in the denominator is so close to zero that we can ignore it.
- Sun Jan 12, 2020 9:09 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reaction Direction
- Replies: 19
- Views: 1077
Re: Reaction Direction
If Q>K then the reaction moves to the left because the concentration of products is greater than the concentration of reactants so the reaction would move towards the side of the reactants to reach equilibrium. If Q<K, then the reaction moves to the right because the concentration of reactants is gr...
- Sun Jan 12, 2020 9:00 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Partial Pressure
- Replies: 19
- Views: 771
Re: Partial Pressure
Usually they should be given or you might have to convert from moles to pressure using the ideal gas equation.
- Sun Jan 12, 2020 8:50 pm
- Forum: Ideal Gases
- Topic: PV = nRT Confusion
- Replies: 4
- Views: 239
Re: PV = nRT Confusion
PV=nRT, the ideal gas equation, can be used to solve for any of the values in the equation if a question asks for it or converting between pressure and molarity.
- Sun Jan 12, 2020 8:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kp vs Kc usage
- Replies: 5
- Views: 195
Re: Kp vs Kc usage
Kp is used when the products and reactants are in the gaseous phase. Kc is used when the products and reactants are in the aqueous phase, so they have a concentration.
- Sun Jan 12, 2020 8:38 pm
- Forum: Ideal Gases
- Topic: partial pressures
- Replies: 7
- Views: 266
Re: partial pressures
The ratio (PO2)^3/(PO3)^2 represents the equilibrium constant K so it stays the same. As a result changing the concentrations of the products and reactants would not change the constant.
- Sun Dec 08, 2019 10:35 pm
- Forum: Biological Examples
- Topic: Heme complex & O2
- Replies: 5
- Views: 333
Re: Heme complex & O2
Yes each heme complex binds to one O2- molecule which is why myoglobin only transports one oxygen molecule at a time.
- Sun Dec 08, 2019 10:32 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: pKa and pKb
- Replies: 2
- Views: 308
Re: pKa and pKb
It is the negative log of the Ka value. A lower pka indicates that an acid is stronger because it shows that the acid more fully dissociates.
- Sun Dec 08, 2019 10:31 pm
- Forum: Naming
- Topic: type of compound
- Replies: 3
- Views: 288
Re: type of compound
It is an amphoteric oxide because it falls under the amphoteric band on the periodic table.
- Sun Dec 08, 2019 10:27 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Types of Salts
- Replies: 7
- Views: 640
Re: Types of Salts
No, but you can differentiate between an acidic, normal, and basic salt. A salt formed from a strong acid and weak base is normally acidic and a salt formed from a strong base and a weak acid is normally basic.
- Sun Dec 08, 2019 10:21 pm
- Forum: Naming
- Topic: Types of Compounds
- Replies: 2
- Views: 270
Re: Types of Compounds
If the electronegativity difference between two atoms is greater than 2, then the bond is normally ionic and if the difference is less than 1.5 then the bond is normally covalent.
- Sun Dec 01, 2019 8:46 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Acid Strength
- Replies: 3
- Views: 256
Re: Acid Strength
In oxacids, increasing the number of oxygen atoms distributes the negative charge over more atoms so the proton is less attracted to only one oxygen so the acid becomes stronger.
- Sat Nov 30, 2019 3:18 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Relative Acidity
- Replies: 4
- Views: 363
Re: Relative Acidity
The more polarizable an anion, the more stable it is, so the more electronegative an atom, the more stable the anion.
- Sat Nov 30, 2019 3:13 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Ka constant
- Replies: 5
- Views: 437
Re: Ka constant
The Ka equilibrium constant represents the strength of an acid in a solution based on how well it can dissociate. Lavelle mentioned that if a Ka value is given, it usually indicates that the element is a weak acid because a strong acid that dissociates completely would have a Ka of close to 1.
- Sat Nov 30, 2019 3:09 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Weak Acids & Bases
- Replies: 6
- Views: 413
Re: Weak Acids & Bases
Some examples of a weak base are ammonia (NH3) and methylamine (CH3NH2) and examples are a weak acid are carbonic acid (H2CO3) and vinegar (C2H4O2).
- Fri Nov 29, 2019 7:18 pm
- Forum: Bronsted Acids & Bases
- Topic: Definition of Bronsted and Lewis
- Replies: 1
- Views: 97
Re: Definition of Bronsted and Lewis
Examples of a lewis acid, but not a bronsted acid are BF3, AlCl3, and metal cations like Mg2+, Li+, Na+ because they accept an electron pair, but don't necessarily donate a proton.
- Sun Nov 24, 2019 10:41 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Drawing molecules
- Replies: 7
- Views: 503
Re: Drawing molecules
Drawing the molecules based on its organic structure will not be covered in 14A, so I don't think you will need to know it for the final.
- Sun Nov 24, 2019 10:35 pm
- Forum: Hybridization
- Topic: Why does hybridization occur
- Replies: 3
- Views: 216
Re: Why does hybridization occur
Hybridization occurs when an atom creates a bond using electrons from both the s and p orbitals. As a result, there is an imbalance in the energy levels, so to equalize it, the s and p orbitals are combined to create hybrid orbitals.
- Sun Nov 24, 2019 10:32 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond angles
- Replies: 7
- Views: 463
Re: Bond angles
The bond angles are less than 120 degrees on the equatorial and less than 90 degrees on the axial.
- Sun Nov 24, 2019 10:29 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: bronsted acid
- Replies: 5
- Views: 292
Re: bronsted acid
A bronsted acid is a molecule that gives up a proton, or a hydrogen atom, to another molecule.
- Sun Nov 24, 2019 10:27 pm
- Forum: Hybridization
- Topic: sigma or pi?
- Replies: 20
- Views: 1200
Re: sigma or pi?
A single bond is a sigma bond and any additional bonds after that connecting the same elements are pi bonds.
- Sun Nov 17, 2019 7:00 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR Angles
- Replies: 4
- Views: 304
Re: VSEPR Angles
We should know the bond angles for the shapes that do not have lone pairs because the angles are constant. However, for the shapes with lone pairs, we need to know that the bond angles for trigonal pyramidal are less than 109.5 degrees.
- Sun Nov 17, 2019 6:43 pm
- Forum: Electronegativity
- Topic: Electron affinity
- Replies: 2
- Views: 277
Re: Electron affinity
Electronegativity is the ability of an atom to attract electrons to itself while electron affinity is the energy released when an electron is added to a neutral atom.
- Sun Nov 17, 2019 6:38 pm
- Forum: Lewis Structures
- Topic: Noble gases
- Replies: 3
- Views: 299
Re: Noble gases
Noble gases from the 3p orbital onwards are able to have an expanded octet because the electrons can expand into the d subshell. As a result, xenon is able to form a covalent bond because it can expand its octet.
- Sun Nov 17, 2019 6:29 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs
- Replies: 5
- Views: 390
Re: Lone Pairs
The ones we have gone over in lecture are bent, trigonal pyramidal, see-saw, and square planar.
- Sun Nov 17, 2019 6:20 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shape of XeF4
- Replies: 2
- Views: 181
Re: Shape of XeF4
When you draw the lewis structure, you see that xenon has an expanded octet which means that there are six bonding regions including the two lone pairs on the xenon and the four bonding pairs to the fluoride. so the shape would be octahedral.
- Sun Nov 10, 2019 8:47 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: formal charge
- Replies: 7
- Views: 448
Re: formal charge
Usually, you only want to find formal charges if the question asks for it, but when drawing lewis structures with or without a charge, you want to calculate the formal charge of each atom and see if all the formal charges add up to the charge of the molecule.
- Sun Nov 10, 2019 7:21 pm
- Forum: DeBroglie Equation
- Topic: De Broglie Equation Derivation and Use
- Replies: 7
- Views: 1196
Re: De Broglie Equation Derivation and Use
It is derived from the equations E=momentum * speed of light and E= hc/wavelength. Combining both of those, you get wavelength= h/momentum. You use the de Broglie equation for any particle with momentum and wavelength properties.
- Sun Nov 10, 2019 7:07 pm
- Forum: Lewis Structures
- Topic: expanded octet
- Replies: 3
- Views: 244
Re: expanded octet
The ones you probably need to know for this class would be sulfur, phosphorus, chlorine, and silicon because their electrons expand into the 3d orbital.
- Sun Nov 10, 2019 7:05 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionization Energy
- Replies: 5
- Views: 604
Re: Ionization Energy
Ionization decreases down a group and increases across a period. The ionization energy decreases down a group because as the number of shells increases, the electrons are shielded from the nucleus, so it takes less energy to remove the last electron. The ionization energy increases across a period b...
- Sun Nov 10, 2019 6:59 pm
- Forum: Octet Exceptions
- Topic: electron number in octet
- Replies: 8
- Views: 629
Re: electron number in octet
Expanded octets usually occur for phosphorus, sulfur, chlorine, and silicon. The number of electrons that a molecule with an expanded octet usually depends on the total number of valence electrons present in the entire molecule and the overall charge of the molecule. An expanded octet usually occurs...
- Sun Nov 03, 2019 10:06 pm
- Forum: Properties of Light
- Topic: Solving for energy of a photon
- Replies: 3
- Views: 211
Re: Solving for energy of a photon
Yes, we did a problem like this in one of the review sessions, and we used the equation En=-hR/n^2 to solve for the change in energy.
- Sun Nov 03, 2019 9:59 pm
- Forum: Trends in The Periodic Table
- Topic: Ionization
- Replies: 5
- Views: 663
Re: Ionization
Oxygen has a lower ionization energy because when you add an electron, it is added to an already half full orbital while for nitrogen, only half the orbital is full. As a result, there is electron-electron repulsion which lowers the ionization energy for oxygen.
- Sun Nov 03, 2019 9:52 pm
- Forum: Ionic & Covalent Bonds
- Topic: Midterm
- Replies: 2
- Views: 187
Re: Midterm
Lavelle said in the lecture that only the information up to 2D exercises in the textbook will be covered.
- Sun Nov 03, 2019 9:51 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge
- Replies: 3
- Views: 159
Re: Formal Charge
You would only have to calculate it if it is specified, but you should calculate the formal charge of the structure to find out if the structure is in its most stable state.
- Sun Nov 03, 2019 9:49 pm
- Forum: Photoelectric Effect
- Topic: Threshold
- Replies: 4
- Views: 490
Re: Threshold
You will normally be given the threshold value, but it is not a constant value. Also, it is hvphoton= threshold +1/2mv^2.
- Sun Oct 27, 2019 9:02 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic VS. Covalent Bond
- Replies: 8
- Views: 476
Re: Ionic VS. Covalent Bond
Ionic bonds occur between a metal and a nonmetal and a covalent bond is between two nonmetals.
- Sun Oct 27, 2019 8:08 pm
- Forum: Lewis Structures
- Topic: Orbitals
- Replies: 9
- Views: 516
Re: Orbitals
Yes, I believe so because you remove electrons from the farthest orbital usually.
- Sun Oct 27, 2019 8:06 pm
- Forum: Lewis Structures
- Topic: Lone Pairs
- Replies: 12
- Views: 613
Re: Lone Pairs
You count the number of electrons that aren't shared in a bond between another molecule. For example in a C-O (single) bond, the oxygen has 3 lone pairs and Carbon has 3 lone pairs.
- Sun Oct 27, 2019 8:03 pm
- Forum: Resonance Structures
- Topic: Formal Charge
- Replies: 5
- Views: 264
Re: Formal Charge
No, I don't believe so because a formal charge is a charge assigned to an atom assuming that electrons are equally shared within a chemical bond.
- Sun Oct 27, 2019 7:55 pm
- Forum: Lewis Structures
- Topic: Choosing the central atom
- Replies: 16
- Views: 804
Choosing the central atom
Is there a rule for choosing the central atom? And are there some atoms that will always be the central atom?
- Sun Oct 20, 2019 11:10 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: spin
- Replies: 3
- Views: 143
Re: spin
According to the Pauli Exclusion Principle, if 2 electrons are in the same orbital, then the spin is paired which means they spin in the opposite direction. Usually the spin starts up.
- Sun Oct 20, 2019 10:55 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: quantum numbers
- Replies: 2
- Views: 147
Re: quantum numbers
If you are given the value of one of the quantum numbers, you can figure out the specific value for the other quantum numbers. For example if you are given a value for n, you can find the possible values of l and ml.
- Sun Oct 20, 2019 10:47 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Stern and Gerlach Experiment: Electron Spin
- Replies: 3
- Views: 112
Re: Stern and Gerlach Experiment: Electron Spin
The Stern and Gerlach experiment revealed how electrons don't have the same spin which differed from the classical prediction. Since electrons can be spun up or down, we use a 4th quantum number, ms which is the spin magnetic number.
- Sun Oct 20, 2019 10:40 pm
- Forum: Properties of Electrons
- Topic: Mass of Proton, Electron and Neutron
- Replies: 2
- Views: 155
Re: Mass of Proton, Electron and Neutron
I believe the mass of the electron is given on the formula sheet. I don't think you will need to know the mass of a proton or a neutron, unless it is given in the problem.
- Sun Oct 20, 2019 6:44 pm
- Forum: Properties of Light
- Topic: Week 3 Homework
- Replies: 9
- Views: 428
Re: Week 3 Homework
I remember Lavelle telling us that the homework due for week 3 should only be on the quantum topics.
- Sun Oct 13, 2019 10:34 pm
- Forum: DeBroglie Equation
- Topic: DeBroglie Equation
- Replies: 9
- Views: 404
Re: DeBroglie Equation
The DeBroglie Equation is only used for any moving particles with momentum and has wavelike properties with wavelength. Light does not have any mass so it cannot be used to calculate momentum.
- Sun Oct 13, 2019 10:28 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: When to use the Bohr Frequency Condition?
- Replies: 3
- Views: 153
Re: When to use the Bohr Frequency Condition?
The Bohr Frequency Condition is used when a high energy electron drops to a lower energy level and the difference in energy is given off as a photon.
- Sun Oct 13, 2019 10:23 pm
- Forum: Significant Figures
- Topic: sig figs and periodic tables
- Replies: 11
- Views: 721
Re: sig figs and periodic tables
The periodic table given on the test was the one on his website, so I would use that one. I would also go to the last decimal place given on the periodic table and not round your final answer till the end.
- Sun Oct 13, 2019 10:20 pm
- Forum: General Science Questions
- Topic: Powerpoint Slides
- Replies: 4
- Views: 270
Re: Powerpoint Slides
I'm not sure if he posts power points of the slides, but I know he has modules for each of the quantum lessons on his website that you can take notes on.
- Sun Oct 13, 2019 10:17 pm
- Forum: *Black Body Radiation
- Topic: Black Body
- Replies: 6
- Views: 482
Re: Black Body
A black body is a physical body that absorbs all electromagnetic radiation regardless of frequency.
- Sun Oct 06, 2019 12:51 am
- Forum: Molarity, Solutions, Dilutions
- Topic: Which Volume to use for M1
- Replies: 6
- Views: 324
Re: Which Volume to use for M1
V1 is usually the initial volume that you use to create the second molarity, so if you are solving for V2, you use the smaller volume in the equation for M1.
- Sun Oct 06, 2019 12:45 am
- Forum: Balancing Chemical Reactions
- Topic: Strategies for Balancing Chemical Equations
- Replies: 12
- Views: 867
Re: Strategies for Balancing Chemical Equations
I balance the element that occurs the least in the equation. For example, if hydrogen occurs two times in the reaction and it is the least occurring element, I balance that first and then move on to the next element that occurs the least. If there's an odd number of moles of an element, you balance ...
- Sun Oct 06, 2019 12:33 am
- Forum: Empirical & Molecular Formulas
- Topic: Decimals to Whole Numbers
- Replies: 6
- Views: 571
Re: Decimals to Whole Numbers
usually you have a margin of error or plus or minus .1. it also depends on what you are using it for. FOr empirical/molecular you can round like 3.8 to 4 (from what I have been told)
- Sun Oct 06, 2019 12:29 am
- Forum: Balancing Chemical Reactions
- Topic: Strategies for Balancing Chemical Equations
- Replies: 12
- Views: 867
Re: Strategies for Balancing Chemical Equations
i start with the elements that are not carbon and then the rest before balancing hydrogen and oxygen
- Sun Oct 06, 2019 12:23 am
- Forum: Empirical & Molecular Formulas
- Topic: Chemical Formulas
- Replies: 2
- Views: 203
Re: Chemical Formulas
There is a formula sheet that will be given for the test, but on the safe side, you should memorize the list of polyatomic ions.
- Sun Oct 06, 2019 12:20 am
- Forum: Empirical & Molecular Formulas
- Topic: Limiting Reactants
- Replies: 4
- Views: 205
Re: Limiting Reactants
If the question asks for it, then you should subtract the grams of the amount of the excess reactant from the grams of the limiting reactant already calculated.