## Search found 102 matches

Thu Mar 12, 2020 10:45 am
Forum: First Order Reactions
Topic: Units for t
Replies: 13
Views: 182

### Re: Units for t

t can be in seconds, minutes, or hours, but MUST be consistent across all terms or it will mess up your calculations.
Thu Mar 12, 2020 10:29 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Approximating X
Replies: 13
Views: 212

### Re: Approximating X

If the k value is very small (i.e. less than 10^-4) then you can approximate.
Thu Mar 12, 2020 10:23 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Frequency Factor
Replies: 6
Views: 130

### Re: Frequency Factor

Used in the Arrhenius equation, the frequency factor is used to describe the rate of molecular collisions.
Wed Mar 11, 2020 4:45 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Collision Model
Replies: 3
Views: 78

### Re: Collision Model

The collision model explains why most collisions between molecules do NOT result in a chemical reaction.
Wed Mar 11, 2020 4:44 pm
Forum: General Rate Laws
Topic: Rate limiting step
Replies: 13
Views: 171

### Re: Rate limiting step

The slowest step in the reaction determines the overall rate law.
Wed Mar 11, 2020 4:39 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: salt bridge
Replies: 11
Views: 99

### Re: salt bridge

The purpose of a salt bridge is to maintain charge balance because the electrons are moving from one half cell to the other. Without a salt bridge, the solution in the anode compartment would become positively charged and the solution in the cathode part would become negatively charged. This would c...
Sun Mar 08, 2020 7:52 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Molecularity
Replies: 12
Views: 167

### Re: Molecularity

Molecularity is the number of molecules that come together to react. It is equal to the sum of the stoichiometric coefficients. (ex. unimolecular, bimolecular, etc.)
Sun Mar 08, 2020 7:48 pm
Forum: Balancing Redox Reactions
Topic: Balancing Basic Redox Reactions
Replies: 6
Views: 86

### Re: Balancing Basic Redox Reactions

In basic solutions you won't have a higher concentration of H+, so you add OH- to counteract the acidity.
Sun Mar 08, 2020 7:46 pm
Forum: Zero Order Reactions
Topic: examples of zero order reactions?
Replies: 6
Views: 90

### Re: examples of zero order reactions?

A zero order reaction describes a reaction where the reaction rate is constant and independent of the concentration of reactants. The rate of reaction is proportional to the zeroeth power of the concentration of reactants.
Sun Mar 08, 2020 7:43 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 13
Views: 195

### Re: Cell Diagrams

You will commonly see an inert solid added to the cell diagram when the other components are in their aqueous form. You need the inert solid when there are no other solid metals in solution.
Sun Mar 08, 2020 7:41 pm
Forum: First Order Reactions
Topic: Graphing 1st order reaction rates
Replies: 6
Views: 59

### Re: Graphing 1st order reaction rates

ln[A] is used in order to yield a graph with a straight line, because otherwise it would yield a graph showing exponential decay. A graph with a straight line can be used to easily find the slope, which is equal to -k, giving us the equilibrium constant.
Sun Mar 01, 2020 8:32 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Spontaneity
Replies: 4
Views: 99

### Re: Spontaneity

While a reaction is spontaneous, its activation energy could be so large that it occurs at an incredibly slow rate.
Sun Mar 01, 2020 8:31 pm
Forum: Balancing Redox Reactions
Topic: Redox Reactions and Acid/Base Reactions
Replies: 9
Views: 154

### Re: Redox Reactions and Acid/Base Reactions

No, redox reactions change the oxidation numbers, which does not occur in all reactions.
Sun Mar 01, 2020 8:28 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: electrodes
Replies: 5
Views: 72

### Re: electrodes

Platinum is commonly used and can be a go-to choice in our examples, but any inert metal will suffice.
Sun Mar 01, 2020 8:26 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: when to use K or Q
Replies: 18
Views: 313

### Re: when to use K or Q

Q should be used when the reaction is not at equilibrium.
Sun Mar 01, 2020 8:25 pm
Forum: General Rate Laws
Topic: order of the reactant
Replies: 3
Views: 71

### Re: order of the reactant

The order of the reaction tells us how the overall rate of reaction is affected by the concentration of the reactants, basically providing a relationship between reaction rate and reactant concentration.
Sun Feb 23, 2020 11:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 4
Views: 74

### Re: Cell Diagrams

Platinum won't get oxidized or reduced. The reactants in the electrolyte get oxidized/reduced at the surface of the inert electrode.
Sun Feb 23, 2020 11:00 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Vant Hoff Equation
Replies: 8
Views: 133

### Re: Vant Hoff Equation

Using deltaH, the Van't Hoff equation relates the equilibrium constant, K, to temperature, T.
Fri Feb 21, 2020 12:45 pm
Forum: Balancing Redox Reactions
Topic: oxidation numbers
Replies: 8
Views: 109

### Re: oxidation numbers

The oxidation number of simple ions is equal to the charge of the ion. When calculating oxidation numbers, we can use known oxidation numbers to find the unknowns.
Fri Feb 21, 2020 12:41 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Voltage of 0
Replies: 3
Views: 57

### Re: Voltage of 0

A galvanic cell is in equilibrium and has a voltage of 0 when Ecathode=Eanode.
Fri Feb 21, 2020 12:37 pm
Forum: Balancing Redox Reactions
Topic: balancing half reactions in a basic solution
Replies: 7
Views: 101

### Re: balancing half reactions in a basic solution

Yes, you must add to both sides in order to form a neutral H20 that would not alter the reaction.
Thu Feb 13, 2020 5:02 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Replies: 19
Views: 368

An adiabatic process occurs without transfer of heat or mass of substances between a thermodynamic system and its surroundings.
Thu Feb 13, 2020 4:59 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: THe first law definition
Replies: 5
Views: 122

### Re: THe first law definition

The first law of thermodynamics tells us that the internal energy of a system can be increased by adding energy to a system or doing work on a system. There are many processes through which this could be accomplished, as long as energy is conserved.
Thu Feb 13, 2020 4:42 pm
Forum: Calculating Work of Expansion
Topic: Work
Replies: 5
Views: 87

### Re: Work

When you are finding the work done in a reversible pathway, you must find the sum of a series of infinitesimal steps, which can be accomplished using an integral. The work done by an irreversible pathway involves a rapid change in volume and pressure, so a different formula is used.
Thu Feb 13, 2020 4:40 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Intensive vs. Extensive
Replies: 15
Views: 384

### Re: Intensive vs. Extensive

Extensive properties depend on your sample size. Specific heat capacity, for example, is an extensive property since it will increase with a greater sample size (requires more energy to increase the temperature of a larger sample by one degree celsius than a smaller sample size).
Thu Feb 13, 2020 4:38 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: spontaneity
Replies: 34
Views: 711

### Re: spontaneity

Gibbs free energy will allow you to determine if the reaction is spontaneous or not (based on the sign). Also enthalpy can be used, as negative enthalpy means the reaction is exothermic since it is releasing heat.
Thu Feb 13, 2020 4:34 pm
Forum: Calculating Work of Expansion
Topic: Positive or negative work
Replies: 15
Views: 318

### Re: Positive or negative work

Determining the sign of work is based on what you decide is your system and what is your surroundings - it's relative. Positive work means that work was done on the system, so it gains energy. Negative work means that work was done by the system, and the system loses energy.
Fri Feb 07, 2020 12:46 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: units
Replies: 4
Views: 70

### Re: units

The biggest concern with units is just making sure that everything you are calculating is in consistent units. A given question may ask for different units, so just pay attention to that and make sure that you use the correct constants.
Fri Feb 07, 2020 12:43 pm
Forum: Phase Changes & Related Calculations
Topic: ΔH
Replies: 4
Views: 74

### Re: ΔH

ΔHfusion and vaporization are given values, so you do not need to worry about memorizing them!
Fri Feb 07, 2020 12:35 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: spontaneous process
Replies: 1
Views: 15

### Re: spontaneous process

A gas will expand to fill any volume. Therefore, if the volume increases, the pressure of the gas will decrease as the gas fills the entire container.
Fri Feb 07, 2020 12:33 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: state occupation of phases
Replies: 7
Views: 51

### Re: state occupation of phases

Gas molecules "occupy more space" since they have a higher entropy, meaning higher disorder, so their location at a given time is less known.
Fri Feb 07, 2020 12:31 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Entropy
Replies: 4
Views: 43

### Re: Entropy

Intensive properties don't depend on sample size, whereas an EXtensive property does depend on sample size. We can conclude that entropy is an extensive property because entropy increases when there is more of a sample present.
Thu Jan 30, 2020 11:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law vs. Standard Enthalpies of Formation
Replies: 5
Views: 81

### Re: Hess's Law vs. Standard Enthalpies of Formation

It will be obvious which method to use since each one has different steps and requirements. So the problem will provide multiple equations for Hess' Law, and a table of standard enthalpies of formation for this method.
Thu Jan 30, 2020 11:18 pm
Forum: Calculating Work of Expansion
Topic: Work equation
Replies: 5
Views: 45

### Re: Work equation

The work equation has a negative sign to represent the loss of energy from the system when it does work on the surroundings. But, the sign of the equation is relative. If compression is occuring (i.e. work is being done on the system) then the work equation has a positive sign.
Thu Jan 30, 2020 11:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Unit
Replies: 6
Views: 42

### Re: Enthalpy Unit

The SI unit for enthalpy is joule per kilogram. However, it can be expressed in different units (not SI).
Thu Jan 30, 2020 11:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: hess's law
Replies: 13
Views: 92

### Re: hess's law

A molecule can only be canceled if it occurs in the same number of moles on the reactant and product side. This means they are balanced and can cancel.
Thu Jan 30, 2020 11:06 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Standard Form of molecule
Replies: 6
Views: 100

### Re: Standard Form of molecule

The standard form of a molecule has given values associated with it. The standard form is observed at 25 degrees Celsius, 1 atm.
Sun Jan 26, 2020 10:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: endothermic
Replies: 8
Views: 75

### Re: endothermic

If the reaction is endothermic, the reaction requires heat and the surroundings cool down. Adding heat to an endothermic reaction means that the forward reaction will be favored.
Sun Jan 26, 2020 10:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpies of Formation
Replies: 4
Views: 31

### Re: Standard Enthalpies of Formation

The standard enthalpies of formation is a value that is given for molecules and used to calculate the overall standard enthalpy of formation of a reaction.
Sun Jan 26, 2020 10:08 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: exo thermic
Replies: 11
Views: 176

### Re: exo thermic

If the temperature is increased in an endothermic reaction, the reverse reaction is favored. Adding heat to a system that overall released heat in the forward direction does not favor the formation of more product.
Sun Jan 26, 2020 10:07 pm
Forum: Phase Changes & Related Calculations
Topic: Heat capacities
Replies: 6
Views: 83

### Re: Heat capacities

Heat capacity is a given value.
Sun Jan 26, 2020 10:06 pm
Forum: Phase Changes & Related Calculations
Topic: Work (w)
Replies: 8
Views: 69

### Re: Work (w)

Work is not considered a state function because the amount of work done is dependent on more than just the initial and final values - it depends on the path taken to get from the initial to final values.
Sun Jan 26, 2020 10:04 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: H2O as a Gas
Replies: 43
Views: 334

### Re: H2O as a Gas

Water is not included if it's in its liquid state because it is considered a solvent. If it is in its gaseous form, then it is included in calculations.
Sun Jan 26, 2020 10:02 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE BOX
Replies: 27
Views: 275

### Re: ICE BOX

If X is smaller than 10^-3, then the affect of subtracting this value from the denominator is negligible.
Sun Jan 26, 2020 10:00 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy
Replies: 5
Views: 71

### Re: Enthalpy

Enthalpy is a state property because the "path" taken to get from the initial to final value is not important.
Sun Jan 26, 2020 9:59 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Gas Constant
Replies: 13
Views: 85

### Re: Gas Constant

Use the gas constant that has the same units as the other values you are using in the calculation. For example, if your pressure is in atm, then use the gas constant that has the unit with atm (so they match and cancel).
Sun Jan 26, 2020 9:57 pm
Forum: Ideal Gases
Topic: Determining N
Replies: 9
Views: 172

### Re: Determining N

N is determined by the moles of gas, or put more simply, the concentration.
Fri Jan 10, 2020 5:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Difference between lies, sits, and shifts
Replies: 4
Views: 33

### Re: Difference between lies, sits, and shifts

These all mean effectively the same thing.
Fri Jan 10, 2020 4:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pressure and Volume
Replies: 8
Views: 56

### Re: Pressure and Volume

Changing the pressure does not affect K, as K is a constant and all of the pressures would change by the same factor. Temperature DOES change K.
Fri Jan 10, 2020 4:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Change in k
Replies: 11
Views: 192

### Re: Change in k

Changing the concentrations of R or P does not affect K because K is a constant. It changes Q, and so you can calculate Q to tell you know the reaction will proceed to return to the given ratio of K.
Fri Jan 10, 2020 4:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: using Kp vs Kc
Replies: 13
Views: 127

### Re: using Kp vs Kc

You can convert between Kp and Kc using the ideal gas law. Kp is used for partial pressures of gases, whereas Kc is used for concentrations.
Fri Jan 10, 2020 4:50 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: K vs Q
Replies: 9
Views: 166

### Re: K vs Q

Q can be thought of as a snapshot of the reaction concentrations at a moment in time. K is a value that does not change, remaining the same throughout the whole reaction. If Q is greater than K, there is more product than would be found when the reaction is at equilibrium, so the reaction will proce...
Sun Dec 08, 2019 2:04 am
Forum: Naming
Topic: cobalt
Replies: 4
Views: 159

### Re: cobalt

You add the -ate when the complex is negatively charged. When it is neutral or positively charged, you leave the name as it normally is.
Sun Dec 08, 2019 2:03 am
Forum: Calculating the pH of Salt Solutions
Topic: pH vs. pOH
Replies: 17
Views: 433

### Re: pH vs. pOH

pH = -log[H+]
pOH = -log[OH-]
Sun Dec 08, 2019 2:01 am
Forum: Dipole Moments
Topic: Melting and Boiling Points
Replies: 9
Views: 301

### Re: Melting and Boiling Points

Hydrogen bonds are, in essence, the strongest type of dipole-dipole interaction. Ionic bonds will always be stronger than dipole-dipole/H bond interactions.
Sun Dec 08, 2019 1:56 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Using Ka or Kb to find pKa or pKb
Replies: 2
Views: 41

### Re: Using Ka or Kb to find pKa or pKb

We will be given the ionization constants (Ka and Kb) if needed
Sun Dec 08, 2019 1:54 am
Forum: Biological Examples
Topic: Cisplatin
Replies: 5
Views: 208

### Re: Cisplatin

In the cis-molecule, the chlorines are on the same side. They bond to adjacent guanines by kicking off a nitrogen on a DNA molecule. The trans-platin version of the molecule has Cl's oriented on opposite sides, so when one of the Cl's binds to a guanine, the DNA Polymerase can easily kick off the Cl...
Sun Dec 08, 2019 1:51 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR and polarity
Replies: 8
Views: 242

### Re: VSEPR and polarity

Basically the only time it will be neutral is when all four atoms in a tetrahedral molecule are the same atom. Lone pairs and varying atoms creates dipoles that affect the net dipole, and therefore polarity, of the molecule.
Sun Dec 08, 2019 1:49 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: polarisability
Replies: 3
Views: 255

### Re: polarisability

I would just know the general trends, we likely won't have to do calculations based off this quation. Polarizability refers to an atom's ability to form instantaneous dipoles, and is based on how large an atom's electron cloud is. Know that the bigger an atom is, the more polarizable it is.
Sun Dec 08, 2019 1:46 am
Forum: Biological Examples
Topic: What specific compounds/ligands do we need to know for the final?
Replies: 7
Views: 217

### Re: What specific compounds/ligands do we need to know for the final?

Yes, porphyrin is tetradentate! It forms a "ring" (chelating ligand) that gives blood its red color.
Sun Dec 08, 2019 1:35 am
Forum: *Shrodinger Equation
Topic: schrodingers equation
Replies: 8
Views: 251

### Re: schrodingers equation

Schrodinger's equation describes the wave function. Solving the equation give you the position and momentum of the wave.
Sun Dec 08, 2019 1:33 am
Forum: Identifying Acidic & Basic Salts
Topic: Knowing strong acids and bases
Replies: 8
Views: 213

### Re: Knowing strong acids and bases

While it is helpful to memorize the strong acids, strong bases can be identified by all cations (bound to OH-) in group 1 and some of group 2.
Mon Nov 25, 2019 5:46 pm
Forum: Naming
Topic: ferrate
Replies: 4
Views: 75

### Re: ferrate

Ferrate is the anion with chemical formula [FeO4]2−
Mon Nov 25, 2019 5:44 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 5
Views: 207

### Re: Resonance

When drawing resonance structures, you still only want the lewis structures with the most "well balanced" formal charges. Note that the negative charge should always go on the most electronegative atom.
Mon Nov 25, 2019 5:41 pm
Forum: Amphoteric Compounds
Topic: Amphiprotic
Replies: 11
Views: 169

### Re: Amphiprotic

Amphiprotic means that something can act as both a proton donor and proton acceptor. The example that Lavelle used in class was water, as it serves both functions in aqueous solutions
Mon Nov 25, 2019 5:40 pm
Forum: Lewis Acids & Bases
Topic: Proton acceptor and proton donor?
Replies: 33
Views: 479

### Re: Proton acceptor and proton donor?

acid = proton donor
base = proton acceptor
Mon Nov 25, 2019 5:37 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: How do you know is an acid is strong or weak?
Replies: 6
Views: 88

### Re: How do you know is an acid is strong or weak?

It is most convenient to memorize the list of strong acids since there aren't that many. However, in more conceptual terms, strong acids completely dissociate in water whereas weak acids only partially dissociate. We see the presence of an equilibrium arrow because some of the compound still remains...
Mon Nov 25, 2019 5:32 pm
Forum: Naming
Topic: roman numerals
Replies: 7
Views: 143

### Re: roman numerals

The roman numeral indicates the charge of the ion. They are used for elements that can have ions with multiple different charges as a way to specify.
Mon Nov 25, 2019 5:30 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground state?
Replies: 6
Views: 275

### Re: Ground state?

Ground state refers to the lowest energy state regardless of whether it's an atom or an ion. Ions are not considered to be in "excited states".
Sun Nov 17, 2019 11:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Drawing molecules
Replies: 12
Views: 192

### Re: Drawing molecules

While you may have to draw a Lewis Structure, you will not need to draw the molecule's VSEPR model. You will just need to know the shape and electron geometry.
Sun Nov 17, 2019 11:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone vs. Bonding Pair
Replies: 6
Views: 103

### Re: Lone vs. Bonding Pair

Lone pairs occupy more space than a bonded pair of electrons, therefore causing greater repulsion from other bonded pairs.
Sun Nov 17, 2019 11:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: dipole moments
Replies: 11
Views: 146

### Re: dipole moments

In a molecule, dipole moments cancel when there are two equal dipoles oriented in the opposite direction.
Sun Nov 17, 2019 11:08 pm
Forum: Hybridization
Topic: Hybridization
Replies: 6
Views: 65

### Re: Hybridization

Hybridization occurs when atomic orbitals fuse together to form new hybridized orbitals.
Sun Nov 17, 2019 11:01 pm
Forum: Ionic & Covalent Bonds
Topic: ionic bonding
Replies: 2
Views: 63

### Re: ionic bonding

The bonds with the most ionic character exist between atoms with the greatest differences in electronegativity.
Sun Nov 17, 2019 10:56 pm
Forum: Lewis Structures
Topic: Oxygen
Replies: 9
Views: 322

### Re: Oxygen

Oxygen most commonly forms a double bond within a molecule because it results in a formal charge of zero. But, it can also form single or triple bonds.
Fri Nov 01, 2019 2:30 pm
Forum: Lewis Structures
Topic: Lone Pairs
Replies: 10
Views: 99

### Re: Lone Pairs

Lone pairs refers to a pair of valence electrons that are shared with another atoms when covalently bonded.
Fri Nov 01, 2019 2:28 pm
Forum: Bond Lengths & Energies
Topic: Lone electron pairs weakening bonds
Replies: 4
Views: 40

### Re: Lone electron pairs weakening bonds

Lone pairs on bonded atoms weaken the bond because of repulsion. Electrons are negatively charged - like charges repel each other, so the repulsion of these clustered electrons weakens the bond.
Fri Nov 01, 2019 2:26 pm
Forum: Ionic & Covalent Bonds
Topic: Transition Metals
Replies: 3
Views: 39

### Re: Transition Metals

Transition metals in the d-block can exist in a wide variety of oxidation states due to their electron configurations. Problems will specify what charge that cation has.
Fri Nov 01, 2019 2:23 pm
Forum: Ionic & Covalent Bonds
Topic: Anions and Cations
Replies: 9
Views: 183

### Re: Anions and Cations

Cations are significantly smaller than anions because they have lost the electrons in their outermost shell. The protons in the nucleus pull the remaining electrons very tightly towards the nucleus, decreasing the atomic radius. Anions, on the other hand, gain electrons to complete their outer shell...
Fri Nov 01, 2019 2:20 pm
Forum: Trends in The Periodic Table
Topic: Noble Gases
Replies: 10
Views: 170

### Re: Noble Gases

Noble gases have a full octet of electrons in their outermost shell, making them stable and virtually unreactive. Since valence electrons determine the chemistry of the atom, noble gases do not exhibit the trends of ionization energy/electron affinity/etc. that we see with atoms with incomplete oute...
Sat Oct 26, 2019 9:58 pm
Forum: Lewis Structures
Topic: Covalent vs Ionic
Replies: 2
Views: 19

### Re: Covalent vs Ionic

Ionic bonds are stronger than covalent bonds. A covalent bond involves overlapping of orbitals while an ionic bond involves charge separation.
Sat Oct 26, 2019 9:54 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration Notation
Replies: 5
Views: 79

### Re: Electron Configuration Notation

Both of those are correct, however, the way Lavelle taught us in class emphasizes the fact that subshells have different energies.
Sat Oct 26, 2019 9:52 pm
Forum: Sigma & Pi Bonds
Topic: Double bond
Replies: 15
Views: 246

### Re: Double bond

One reason that a double bond may exist between two atoms is because it is the most stable, energetically. We sometimes add double bonds when drawing lewis structures because it decreases the number of lone pairs of electrons in the molecule.
Fri Oct 25, 2019 7:30 pm
Forum: Lewis Structures
Topic: Anion
Replies: 7
Views: 112

### Re: Anion

An anion is indicated in a Lewis structure by drawing brackets around the molecule with the overall charge written out next to it. When determining how to draw this Lewis structure, you sum the valence electrons of all atoms in the molecule. Then, you add the number of electrons indicated by the cha...
Fri Oct 25, 2019 7:27 pm
Forum: Resonance Structures
Topic: Bond lengths
Replies: 4
Views: 51

### Re: Bond lengths

Yes. Experimentally, we can see that the bond length is an average of single and double bond lengths. This is the resonance hybrid structure of the molecule.
Sun Oct 20, 2019 11:25 pm
Forum: Properties of Electrons
Topic: Wave-like and particle-like properties
Replies: 7
Views: 110

### Re: Wave-like and particle-like properties

Wave-particle duality asserts that all objects exhibit both wave-like and particle-like properties. Particles with a very small mass, such as electrons, exhibit this wave-particle duality, whereas something that has a very large mass, like a car, will only really show particle-like properties.
Sun Oct 20, 2019 11:22 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Probability of finding an electron at a certain location
Replies: 4
Views: 79

### Re: Probability of finding an electron at a certain location

A good rule of thumb for determining the probability of finding an electron at a certain location is the orbital diagrams. For the p-orbitals, for example, the probability of finding an electron where the nodes intersect is 0, whereas the probability of finding one within the nodes is fairly equal a...
Sun Oct 20, 2019 11:20 pm
Forum: Significant Figures
Topic: Sig Figs at the Beginning or End
Replies: 14
Views: 456

### Re: Sig Figs at the Beginning or End

All calculations should be done while keeping as many sig figs as possible (or as many as your calculator allows). Then, when you round at the end, you can be confident that your final rounded answer is as accurate as possible.
Sun Oct 20, 2019 11:13 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: spin
Replies: 3
Views: 49

### Re: spin

Parallel spins are not impossible according to Pauli Exclusion Principle. Conceptually, this is because electrons repel each other and their spins cannot be oriented in the same direction. It is considered most common to have the first spin up and the second one down.
Sun Oct 20, 2019 11:09 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Applying Pauli Exclusion Principle and Hund's Rule
Replies: 5
Views: 87

### Re: Applying Pauli Exclusion Principle and Hund's Rule

Pauli Exclusion Principle and Hund's Principle both come into play when determining how to fill electron orbitals. We can use PEP to ensure that two electrons do not have the same spin within the same orbital. We use Hund's Principle to ensure that orbitals are filled from lowest energy level to hig...
Sun Oct 13, 2019 3:53 pm
Forum: Properties of Light
Topic: speed of light
Replies: 10
Views: 107

### Re: speed of light

For the intents and purposes of this class, the constant for the speed of light, c, always equals 3.00 x 10^8. However, it is important to note that the speed of light is not constant as it moves from medium to medium. When light enters a denser material, the speed and wavelength of light decrease w...
Sun Oct 13, 2019 3:47 pm
Forum: Properties of Electrons
Topic: Diffraction
Replies: 6
Views: 69

### Re: Diffraction

Constructive interference describes when the waves are in phase (peaks are overlapping). When this occurs, the amplitudes of the peaks are added to create one larger wave. Destructive interference describes when the waves are out of phase. The peaks do not overlap, and the amplitudes are subtracted.
Sun Oct 13, 2019 3:39 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic spectroscopy changes in energy
Replies: 1
Views: 31

### Re: Atomic spectroscopy changes in energy

The energy change from n=2 to n=1 is the greatest because of the electron's attraction to the positively charged protons in the nucleus. When the electron makes this energy change, it is actually releasing energy because it wants to be pulled in towards the nucleus. The attraction is greatest when i...
Sun Oct 13, 2019 3:34 pm
Forum: Photoelectric Effect
Topic: ejecting electons
Replies: 6
Views: 100

### Re: ejecting electons

As stated above, one photon can never eject multiple electrons. You may be referring to the energy level of the incoming photon in comparison to the threshold energy of the ejected electron. If the incoming photon has an excess of energy compared to the threshold energy needed to eject an electron, ...
Sun Oct 13, 2019 3:30 pm
Forum: Photoelectric Effect
Topic: Mass of Neutron
Replies: 1
Views: 41

### Re: Mass of Neutron

The mass of a neutron is 1.674929 x 10-27 kg.
Thu Oct 10, 2019 4:22 pm
Forum: Properties of Electrons
Topic: Electron energy levels- conceptual stuff
Replies: 3
Views: 34

### Re: Electron energy levels- conceptual stuff

Electrons can released quantized amounts of energy (in the form of a photon) to "jump" down energy levels. Electrons are attracted to the nucleus because the negative charge of the electron is attracted to the positive charge of the protons. So, when it is decreasing energy levels, it is a...
Sun Oct 06, 2019 9:50 pm
Forum: SI Units, Unit Conversions
Topic: Temperature
Replies: 6
Views: 107

### Re: Temperature

When it comes to precision, its always best to do all of the calculations using as many decimal places and sig figs as possible. Then, you can round your final answer to the correct number of sig figs and know it will be as precise as possible.
Sun Oct 06, 2019 9:48 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Word Problem Efficiency
Replies: 7
Views: 252

### Re: Word Problem Efficiency

I find it helpful to circle all of the relevant parts of the equation and then rewrite it in an abbreviated version. So, for example, if the problem is talking about compounds reacting with each other, I prefer writing all of them in their chemical symbols and writing out the actual equation.
Sun Oct 06, 2019 9:41 pm
Forum: Balancing Chemical Reactions
Topic: Fractions
Replies: 34
Views: 566

### Re: Fractions

In past chemistry classes, we have converted the fraction to a decimal and rounded to the correct number of sig figs. I assume Lavelle will prefer we do this since that is typically how figures are reported on lab reports and other experimental documents.
Sun Oct 06, 2019 9:38 pm
Forum: Significant Figures
Topic: When do zeros count?
Replies: 5
Views: 89

### Re: When do zeros count?

The fact that 3000 has 1 sig fig but 3000. has 4 sig figs has to do with the accuracy of a measurement. If you reported a measurement as 3000 lbs, someone could infer that the scale you were using was accurate to the nearest thousand. However, if you reported a measurement as 3000. lbs, someone can ...