Search found 103 matches
- Sun Mar 15, 2020 11:44 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electrode size [ENDORSED]
- Replies: 2
- Views: 292
Re: Electrode size [ENDORSED]
The size of the electrode should not change the potential of the cell because it is solid and the reaction quotient does not take solids or liquids into consideration
- Sun Mar 15, 2020 11:43 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation Energy
- Replies: 4
- Views: 346
Re: Activation Energy
Normally if the activation energy is higher, the reaction rate is slower because it requires more energy.
- Sun Mar 15, 2020 11:42 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: ΔGionization
- Replies: 10
- Views: 795
Re: ΔGionization
I believe that deltaG ionization is calculated the same as normal standard gibbs free energy.
- Sun Mar 15, 2020 11:40 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy Ionization
- Replies: 2
- Views: 260
Re: Gibbs Free Energy Ionization
I don't think so. I calculated Gibbs free energy ionization the same way as standard gibbs free energy.
- Sun Mar 15, 2020 11:40 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation/Reduction
- Replies: 17
- Views: 1067
Re: Oxidation/Reduction
You would consider one specific atom within a molecule
- Sat Mar 14, 2020 7:04 pm
- Forum: General Rate Laws
- Topic: Rate Law
- Replies: 6
- Views: 545
Re: Rate Law
An integrated rate law gives the rate of reaction based on time, while a differential rate law gives the rate of reaction based on reactant concentration.
- Sat Mar 14, 2020 7:02 pm
- Forum: Balancing Redox Reactions
- Topic: balancing h and o
- Replies: 7
- Views: 508
Re: balancing h and o
I usually balance the O first using H2O and then balance the H using H+ afterwards
- Mon Mar 09, 2020 12:21 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration Cells
- Replies: 3
- Views: 252
Re: Concentration Cells
A concentration cell has the same anode and cathode, which means that electron transfer comes from differences in concentration. When the two electrodes are connected, electrons from the cell with the lower concentration (the anode) move to the cell with the higher concentration (cathode) to create ...
- Mon Mar 09, 2020 12:17 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration
- Replies: 9
- Views: 518
Re: Concentration
If you are referring to a galvanic cell, you would use the Nernst Equation, which is Ecell = Enot - RT/nF lnQ, where Q = [products]/[reactants]. If you are given all other variables, you can solve for the concentration of the anode or cathode.
- Mon Mar 09, 2020 12:16 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: E cell
- Replies: 9
- Views: 584
Re: E cell
E standard cell, which is sometimes called Enot, is the standard state cell potential at state conditions, which is 25C, 1 atm. Ecell is the cell potential at non standard state condition. This value can be found by using the Nernst Equation.
- Mon Mar 09, 2020 12:14 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Anode concentration
- Replies: 3
- Views: 252
Re: Anode concentration
To find anode concentration, you should use the Nernst Equation, which is E = Enot - RT/nF lnQ, where Q = [products]/[reactants].
- Mon Mar 09, 2020 12:11 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration Cell
- Replies: 5
- Views: 447
Re: Concentration Cell
A concentration cell has the same compound as both anode and cathode. This makes the Enot equal to zero. This reaction is driven by the difference in concentrations of both the anode and cathode, with the anode being the side with the lower concentration
- Sun Mar 01, 2020 10:33 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: electron flow
- Replies: 4
- Views: 186
Re: electron flow
The term voltage refers to the flow of electrons. If voltage is moving from left to right, then electrons is flowing from right to left. Because electricity refers to the presence and flow of electrons, they can be used interchangeably.
- Sun Mar 01, 2020 10:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: cell potential
- Replies: 15
- Views: 762
Re: cell potential
deltaG = -nFE, so if E is positive, deltaG would be negative, showing that the reaction is spontaneous. If E is negative, then deltaG is negative, showing that the reaction is not spontaneous.
- Sun Mar 01, 2020 10:28 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: salt bridge
- Replies: 9
- Views: 564
Re: salt bridge
Some common salts used in a salt bridge are sodium chloride, potassium chloride, and potassium nitrate. The electrolyte chosen must easily dissociate and not react with any of the chemicals in the cell.
- Sun Mar 01, 2020 10:25 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2
- Replies: 4
- Views: 282
Re: Test 2
He will most likely give us a paper of the standard cell potentials.
- Sun Mar 01, 2020 10:23 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams
- Replies: 6
- Views: 431
Re: Cell Diagrams
It shouldn't matter what order you write Fe2+ and Fe3+ in because they are in the same phase.
- Sun Feb 23, 2020 4:58 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation number of H
- Replies: 6
- Views: 420
Re: Oxidation number of H
Generally, H has a charge of +1. This is true when it acts as a cation or when it is bound to a nonmetal. H will have a charge of -1 only when it is bonded to a cation/metal.
- Sun Feb 23, 2020 4:55 pm
- Forum: Balancing Redox Reactions
- Topic: Figuring Out Electrons Transferred for a Problem Where Both Sides Have The Same Oxidation Number
- Replies: 3
- Views: 204
Re: Figuring Out Electrons Transferred for a Problem Where Both Sides Have The Same Oxidation Number
When solving the half reaction for O3 -> O2, both sides must be balanced by using H2O and H+. This would make the equation O3 + 2H+ -> O2 + H2O, but now the charges on each side are not balanced. So, you would add 2e- on the left side to make the charges of both sides equal to zero.
- Sun Feb 23, 2020 4:52 pm
- Forum: Balancing Redox Reactions
- Topic: spontaneous
- Replies: 15
- Views: 740
Re: spontaneous
The standard reaction potential is positive when the reaction is spontaneous.
- Sun Feb 23, 2020 4:51 pm
- Forum: Balancing Redox Reactions
- Topic: Adding H2O and OH- to Balance
- Replies: 5
- Views: 293
Re: Adding H2O and OH- to Balance
If you're using OH- to balance an equation, I'm going to assume the reaction is occurring under basic conditions. First, balance all elements except for hydrogen and oxygen. Then, add H2O to balance the oxygen on the opposing side. Then, balance the hydrogen by using H+, and then the charges by usin...
- Sun Feb 23, 2020 4:44 pm
- Forum: Balancing Redox Reactions
- Topic: Basic and Acidic Conditions
- Replies: 5
- Views: 375
Re: Basic and Acidic Conditions
When balancing a reaction in an acidic solution, balance the equations by using H3O+ and H2O. If in a basic solution, balance by using OH- and H2O. Everything else will remain the same.
- Sun Feb 16, 2020 5:19 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: q of ice and q of water
- Replies: 8
- Views: 1455
Re: q of ice and q of water
If ice is placed in water, the system will attempt to equilibrate with heat flow from the water to the ice. Therefore, qWater = -qIce. This can also be derived from the fact that qWater + qIce = 0, since all heat is being exchanged between the 2 objects and nothing else.
- Sun Feb 16, 2020 5:13 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible vs Irreversible
- Replies: 13
- Views: 815
Re: Reversible vs Irreversible
For irreversible reactions, pressure is held constant as temperature changes, while reversible reactions show the change in both temperature and pressure. For irreversible reactions, work = - PdeltaV. For reversible, work = - nRTln (V2/V1), which represents an integral. In addition, entropyTotal = 0...
- Sun Feb 16, 2020 5:06 pm
- Forum: Calculating Work of Expansion
- Topic: work = 0
- Replies: 14
- Views: 1263
Re: work = 0
Because work is equal to Pexternal*deltaV, in a vacuum there is no external pressure, making work = 0. The system is not doing work on the surroundings because the surroundings are not pushing back.
- Sun Feb 16, 2020 5:04 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: delta h and constant temp and pressure
- Replies: 4
- Views: 303
Re: delta h and constant temp and pressure
DeltaH is simply q at constant temperature, so it is the same by default. At constant pressure, deltaH is for a phase change.
- Sun Feb 16, 2020 5:01 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: isolated system
- Replies: 16
- Views: 744
Re: isolated system
Yes, an isolated system would have w = 0 and q = 0 because no work can be done on or by the system and no heat can be exchanged. This also means that deltaU would equal zero because interna energy = q + w.
- Sun Feb 09, 2020 11:18 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Spontaneous vs Favorable
- Replies: 8
- Views: 393
Re: Spontaneous vs Favorable
Spontaneous and favorable refers to the same thing: the reaction will occur without external energy being added.
- Sun Feb 09, 2020 11:17 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta U
- Replies: 7
- Views: 386
Re: Delta U
DeltaU = 0 when there is an isothermal expansion. Although work is used, and heat is consequently lost, heat flow from the surroundings replaces the heat lost, so temperature remains constant. If we know that deltaU = 0, and that deltaU = w + q, then q = -w. We can confirm that w is a negative value...
- Sun Feb 09, 2020 11:12 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: m and n in heat capacity
- Replies: 4
- Views: 164
Re: m and n in heat capacity
Mass and moles in a problem usually refers to the same amount of a chemical because the two values can be converted into each other. When using mass, you calculate using the specific heat capacity, which gives joules per gram degree Celsius. When using moles, you calculate using molar heat capacity,...
- Sun Feb 09, 2020 11:05 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: mCdeltaT
- Replies: 3
- Views: 134
Re: mCdeltaT
q = mCdeltaT should be used when temperature is changing. The delta shows that we take the final and initial temperatures into consideration, and all other variables are constant. When changing from one phase to another, the temperature does not change - just the phase. The q for the phase change ca...
- Sun Feb 09, 2020 11:02 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: work on the system or by the system
- Replies: 4
- Views: 236
Re: work on the system or by the system
If work is done by the system, then w should be positive (system is gaining heat). If work is done on the system, then w should be negative (system is losing heat).
- Sun Feb 02, 2020 10:58 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: work
- Replies: 3
- Views: 160
Re: work
Remember the equation used to calculate work: w = -P (deltaV). If volume were to decrease, then work would be positive, meaning that the surroundings did work on the system. If the volume increased, then work would be positive, meaning the system did work on the surroundings. The example Lavelle use...
- Sun Feb 02, 2020 10:49 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: State Property
- Replies: 5
- Views: 148
Re: State Property
A state property is a value that does not depend on the path you take to get to a state, as long as you get to the final state. Enthalpy is a state property because this value only cares about the final and initial properties.
- Sun Feb 02, 2020 10:45 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 4
- Views: 257
Re: Hess's Law
I usually solve these problems by first lining up all the reactions so unnecessary reactants and products cancel out, flipping equations and multiplying by a coefficient when necessary. Keep in mind which equations you flip and change so you can also flip the sign or multiply the delta H. Then, you ...
- Sun Feb 02, 2020 10:37 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: q vs H
- Replies: 9
- Views: 431
Re: q vs H
Heat transfer refers to q
- Sun Feb 02, 2020 10:36 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond enthalpy calculations
- Replies: 4
- Views: 232
Re: Bond enthalpy calculations
At least for me, I think the best way to do these problems is to draw the lewis structures to figure out which bonds are formed and broken in the duration of the reaction
- Sun Jan 26, 2020 11:35 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: 6C.13
- Replies: 3
- Views: 144
Re: 6C.13
Stronger bases form weaker conjugate acids. Higher pKa shows weaker conjugate acids because pKa is the negative log of Ka, which shows how much an acid would dissociate. To rank the compounds from weakest to strongest base, rank them in order of increasing pKa.
- Sun Jan 26, 2020 11:33 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE BOX
- Replies: 27
- Views: 718
Re: ICE BOX
If the x is < 10^-3, then you can assume that the x has no effect on the denominator.
- Sun Jan 26, 2020 11:29 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure & temperature in chemical equilibria
- Replies: 3
- Views: 79
Re: Pressure & temperature in chemical equilibria
When pressure increases, the reaction shift towards the side with less gas moles, and when pressure decreases, the reaction shifts towards the side with more gas moles. Shifts in temperatures depend if the chemical reaction is exothermic or endothermic. If endothermic and temperature increases, then...
- Sun Jan 26, 2020 11:23 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Finding Ka from pH
- Replies: 5
- Views: 273
Re: Finding Ka from pH
You know that [H3O+] = 10^-pH and [OH-] = 10^-pOH. You can get the Ka or Kb values from using the [H3O+] and [OH-] respectively.
- Sun Jan 26, 2020 11:22 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Negative Square Root solving an ICE box
- Replies: 13
- Views: 473
Re: Negative Square Root solving an ICE box
You should not receive a negative square root. You most likely did something wrong in the math and should check your work
- Sun Jan 19, 2020 9:33 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pa and Pb
- Replies: 4
- Views: 192
Re: Pa and Pb
Pa is for acids and Pb is for bases. Depending on if you are solving for pH or pOH, use Pa to find pH and Pb to find pOH.
- Sun Jan 19, 2020 9:29 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE Tables
- Replies: 13
- Views: 407
Re: ICE Tables
H2O is usually not included in its liquid form because it has a concentration of 1 at all times.
- Sun Jan 19, 2020 9:28 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: exothermic/endothermic rxns
- Replies: 4
- Views: 143
Re: exothermic/endothermic rxns
In an endothermic or exothermic reaction, you can treat heat as a reactant or product depending on the reaction. In an endothermic reaction, heat is required, so heat would be considered a reactant. In an exothermic reaction, heat is released, so it would be considered a product. If you were to incr...
- Sun Jan 19, 2020 9:25 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: H20 in the ICE table
- Replies: 26
- Views: 1342
Re: H20 in the ICE table
When doing an ICE table, do not include water, liquids, or solids, as these do not have concentrations.
- Sun Jan 19, 2020 9:24 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Exo/Endo-thermic Rxns
- Replies: 5
- Views: 243
Re: Exo/Endo-thermic Rxns
If the reaction is endothermic (requires heat), pretend like heat is a reactant in the equation. [ A + B + heat -> C ] From here, you can treat an increase/decrease in temperature as an increase/decrease in reactant. If temperature increases in an endothermic reaction, then the reaction will shift r...
- Sun Jan 12, 2020 11:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: solids and liquids
- Replies: 5
- Views: 136
Re: solids and liquids
Solids and liquids are not included in the K calculation because K is calculated using concentrations. Solids and liquids do not have concentrations, so they cannot affect the equilibrium.
- Sun Jan 12, 2020 11:35 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K's
- Replies: 3
- Views: 114
Re: K's
Kc is the equilibrium constant using concentrations, while Kp is the equilibrium constant using partial pressures. Both are calculated the same way.
- Sun Jan 12, 2020 11:34 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5G.9
- Replies: 3
- Views: 242
Re: 5G.9
D and E will remain the same. Both are equation used to find K of the reaction in the forward and reverse direction. This ratio is a fixed constant.
- Sun Jan 12, 2020 11:32 pm
- Forum: Ideal Gases
- Topic: ICE Table
- Replies: 9
- Views: 445
Re: ICE Table
Change in molar concentration is usually positive on the product side because product are being created from the reactants. This means that the reactants must have a negative change in concentration.
- Sun Jan 12, 2020 11:30 pm
- Forum: Ideal Gases
- Topic: K and Units
- Replies: 7
- Views: 288
Re: K and Units
K does not have any units because it is calculated using an approximation of a compound's chemical activity, which is unit-less.
- Sat Dec 07, 2019 9:08 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: 17.35 Chelating Compounds
- Replies: 7
- Views: 1194
Re: 17.35 Chelating Compounds
How do you determine at what point the nitrogens are too far away to bond to the same metal atom? I think it's more of a common sense thing. If the nitrogens are on complete opposite sides of the benzene ring, it would be impossible for them to bond to the same metal atom. The ideal distance is nit...
- Sat Dec 07, 2019 9:06 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: chelating ligands [ENDORSED]
- Replies: 51
- Views: 95293
Re: chelating ligands [ENDORSED]
Does anyone know what Dr. Lavelle means when he says: atom with lone pair --- spacer atom --- spacer atom --- atom with lone pair The only part i dont understand is spacer atom. What does spacer atom mean? Conceptually I see why C is the correct answer i am just unfamiliar with this terminology Spa...
- Wed Nov 27, 2019 11:41 am
- Forum: Naming
- Topic: Naming Coordination Compound with Iron
- Replies: 4
- Views: 428
Re: Naming Coordination Compound with Iron
Iron is called ferrate because it is derived from its latin name ferrum. Because the periodic table refers to iron by its latin name (Fe), then we also take the latin root while naming.
- Wed Nov 27, 2019 11:37 am
- Forum: Naming
- Topic: polydentate?
- Replies: 7
- Views: 426
Re: polydentate?
polydentate refers to the bonding of a ligand to more than one binding site of a central ion. This usually refers to lone pair donating sites on the central atom.
Re: 9C.1
a. hexacyanoferrate (II) - there are 6 cyanide groups, and 1 iron atom; iron becomes ferrate, and because the overall charge of the coordination compound is negative, it receives the -ate suffix. You can tell the iron has a +2 charge because each cyanide has a -1 charge (x6) and the overall charge i...
- Wed Nov 27, 2019 11:29 am
- Forum: Naming
- Topic: Naming Convention of Metal Anions
- Replies: 5
- Views: 359
Re: Naming Convention of Metal Anions
The metal anion receives the -ate suffix when the coordination compound is negative overall
- Wed Nov 27, 2019 11:27 am
- Forum: Naming
- Topic: Self-test 9C.1B
- Replies: 2
- Views: 229
Re: Self-test 9C.1B
a. The name should be pentamminebromidocobalt (III) sulfate. This is because there are 5 ammonia groups, 1 bromide atom, 1 cobalt with a +3 charge, and a sulfate.
b. The formula is [Cr(NH3)4(OH2)2] Br3
b. The formula is [Cr(NH3)4(OH2)2] Br3
- Wed Nov 20, 2019 4:01 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Is ICl2- Polar or Non-polar?
- Replies: 2
- Views: 569
Re: Is ICl2- Polar or Non-polar?
ICl2- would be nonpolar because dipoles are created only from bonded electrons. The 3 lone pairs do not have a strong enough force to create a dipole in this molecule.
- Wed Nov 20, 2019 3:59 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Big Molecule
- Replies: 2
- Views: 181
Re: Big Molecule
I believe the best way would be to treat this molecule as a hydrocarbon chain with the nitrogen on the end. The nitrogen will most likely be double bonded to the end carbon, but be sure to check how many electrons the molecule should have and formal charges.
- Wed Nov 20, 2019 3:57 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Can linear molecular shapes have lone pair?
- Replies: 4
- Views: 507
Re: Can linear molecular shapes have lone pair?
Many atoms with multiple electron density regions can create linear molecules with the right number of lone pairs. AX2, AX2E2, AX2E3, and AX2E4 are all linear with lone pairs.
- Wed Nov 20, 2019 3:53 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Ionic Bonds
- Replies: 4
- Views: 330
Re: Ionic Bonds
Ionic bonds are normally formed between any metal and any nonmetal because of their difference in electronegativity, which allows one atom, the anion/metal, to "take" electrons away from the cation/nonmetal. Metals include both the alkali and alkali-earth metals, as well as some transition...
- Wed Nov 20, 2019 3:50 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: N2O Lewis Structure/Pi and Sigma Bonds
- Replies: 2
- Views: 738
Re: N2O Lewis Structure/Pi and Sigma Bonds
N is the central atom because it is the least electronegative and because if formal charges are calculated, placing N as the central atom allows each atom to have the lowest FC. There are two sigma bonds and two pi bonds. The N-O single bond is a single sigma bond, while triple bond between N and N ...
- Wed Nov 13, 2019 2:05 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: 3F19.c.
- Replies: 2
- Views: 140
Re: 3F19.c.
Although both molecules are composed of the same atoms, they have different structures which impacts the types of bonds they make. Both molecules create induced dipole-induced dipole bonds, but the strength of these forces differ because of the size of the molecules. Pentane is a smaller molecule so...
- Wed Nov 13, 2019 1:55 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: 3F.5 (b)
- Replies: 4
- Views: 531
Re: 3F.5 (b)
Butanol has the strongest intermolecular bonds because of the -OH group that allows it to create hydrogen bonds between molecules. Diethyl ether has no OH group nor any strong partial positives/partial negatives, so the strongest bond it can make is a london dispersion force, which is the weakest of...
- Wed Nov 13, 2019 1:51 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: 3F13
- Replies: 6
- Views: 440
Re: 3F13
For this problem, the choice showing dipole-dipole interactions between the molecules has the strongest attraction. In choice II, the partial positive H are nearest to the partial negative Cl, giving these molecules the strongest intermolecular interaction. In addition, you know that different molec...
- Wed Nov 13, 2019 1:47 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: melting points
- Replies: 5
- Views: 167
Re: melting points
NaCl's ionic bonding is much stronger than the covalent bonds holding HCl together. Because the bond is stronger, more energy is needed to break the bond, resulting in a higher melting point.
- Wed Nov 13, 2019 1:45 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: 3F3 HW Help
- Replies: 1
- Views: 115
Re: 3F3 HW Help
Dipole-dipole interactions are different than london dispersion forces. Dipole-dipole interactions occur between the partially positive charged atoms of one molecule and the partially negative charged atoms of another molecule. These partial positives occurs as a result of differences in electronega...
- Sun Nov 10, 2019 10:34 pm
- Forum: Lewis Structures
- Topic: Lewis Dot Structures
- Replies: 7
- Views: 355
Re: Lewis Dot Structures
Because we have not discussed shape yet, which depends heavily on electron placement, it does not matter which side the lone electron goes on.
- Sun Nov 10, 2019 10:32 pm
- Forum: Dipole Moments
- Topic: dipole moments
- Replies: 2
- Views: 87
Re: dipole moments
Dipole moments have many names, which include van der waals forces and london dispersion forces. Basically, the electron cloud around an atom can be influenced by the temporary positive attraction of another atom it is not bonded to. This temporary interaction creates a weak intermolecular bond betw...
- Sun Nov 10, 2019 10:24 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: formal charge
- Replies: 7
- Views: 407
Re: formal charge
Formal charge is really mostly used to find the most stable resonance structure, so I would calculate it if a molecule has more than just single bonds
- Tue Nov 05, 2019 11:51 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Midterm
- Replies: 3
- Views: 331
Re: Midterm
No, that will not be on the midterm
- Tue Nov 05, 2019 11:32 pm
- Forum: Properties of Light
- Topic: Rydberg Equation
- Replies: 5
- Views: 337
Re: Rydberg Equation
I think we should just know the portion of the EM spectrum it corresponds to. I don't think there will be any in-depth questions on it
- Wed Oct 30, 2019 3:10 am
- Forum: Trends in The Periodic Table
- Topic: Noble Gas
- Replies: 4
- Views: 144
Re: Noble Gas
The noble gases are included in all trends except electronegativity and electron affinity. This is because noble gases have a full valence shell of electrons, which means that they are in their most stable state. Because of this, they would not attempt to attract any electrons from another source, r...
- Wed Oct 30, 2019 3:07 am
- Forum: Trends in The Periodic Table
- Topic: Ionization Energy
- Replies: 5
- Views: 319
Re: Ionization Energy
Ionization increases as you go up and to the right because, as you move to the right, the atoms have more protons in their nucleus, which exhibit a greater nuclear charge. This stronger positive charge attracts electrons more heavily, which makes it difficult for an electron to be pulled away. The e...
- Wed Oct 30, 2019 3:04 am
- Forum: Trends in The Periodic Table
- Topic: Ionization Energy
- Replies: 4
- Views: 200
Re: Ionization Energy
The best way to tell which atom has the lowest ionization energy is by memorizing the periodic trends. Ionization energy increases as you go up and to the right. This is because ionization energy is defined as the amount of energy needed to remove an electron. As you move towards the right side of t...
- Wed Oct 30, 2019 2:59 am
- Forum: Trends in The Periodic Table
- Topic: Summary of Periodic Trends [ENDORSED]
- Replies: 2
- Views: 110
Re: Summary of Periodic Trends [ENDORSED]
I'm not sure which ones we'd need to memorize for sure, but it's best to remember atomic radius, electron affinity, ionization energy, and electronegativity. Atomic radius increases towards the bottom left. Electron affinity increases towards the top right. Ionization energy and electronegativity in...
- Wed Oct 30, 2019 2:41 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Question 1E 1
- Replies: 3
- Views: 188
Question 1E 1
Question 1E-1 states: w hich of the following increase when an electron in a lithium atom undergoes a transition from the 1s-orbital to a 2p-orbital? (a) Energy of the electron. (b) Value of n. (c) Value of l. (d) Radius of the atom. Which answers would be different for a hydrogen atom and in what w...
- Wed Oct 23, 2019 1:34 am
- Forum: Trends in The Periodic Table
- Topic: Ionic Radius
- Replies: 4
- Views: 179
Re: Ionic Radius
For ground state atoms, the ionic radii changes from bigger to smaller across a period because as the number of protons increases, the effective nuclear charge also increases, which pulls the electrons closer to the nucleus. However, anions follow a different pattern because they are bigger than the...
- Wed Oct 23, 2019 1:28 am
- Forum: Quantum Numbers and The H-Atom
- Topic: 1D.13
- Replies: 3
- Views: 189
Re: 1D.13
You know that a d subshell corresponds to l = 2, and the ml is given by -l to l. Therefore, there are 5 values of ml: -2, -1, 0, 1, 2. You can also use the equation ml = 2l + 1 to find the value of ml.
- Wed Oct 23, 2019 1:26 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Energy of Electrons
- Replies: 6
- Views: 188
Re: Energy of Electrons
The energy of an electron increases when it moves up an energy level. This is because energy, in the form of a photon, can excite an electron to a higher state. Conversely, when an electron moves down an energy level, it loses energy.
- Wed Oct 23, 2019 1:22 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Subshell vs. Orbital
- Replies: 9
- Views: 1266
Re: Subshell vs. Orbital
Shells are divided into subshells, which are further divided into orbitals. The principle quantum number n gives the shell, while the angular momentum number l gives the subshell. The last main quantum number, ml, which is the magnetic quantum number, gives the orbital of the electron.
- Wed Oct 23, 2019 1:17 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: 1 B27
- Replies: 5
- Views: 482
Re: 1 B27
On this problem, you are given the mass and uncertainty in velocity. You can use these numbers to solve for the uncertainty in momentum using the equation p = mv. You can then use this calculated value of p in the Heisenberg Uncertainty Principle, which is defined as deltaP*deltaX >= h / (4pi). Rear...
- Wed Oct 16, 2019 3:31 am
- Forum: Properties of Electrons
- Topic: Intensity vs. Energy
- Replies: 10
- Views: 376
Re: Intensity vs. Energy
In the photoelectric experiment, light was acting as a particle known as a photon. Increasing the intensity of the light changed only the number of photons being used and nothing else. This is why increasing intensity did not affect the electrons being emitted. A single photon must have enough energ...
- Wed Oct 16, 2019 3:28 am
- Forum: Properties of Electrons
- Topic: 1B.5
- Replies: 2
- Views: 150
Re: 1B.5
An eV is an electron volt, so a keV is a kilo-electron volt. To convert this unit to Joules, first multiply by 1000 eV/1keV to get the number in normal eV units. Use the conversion factor 1 eV = 1.602 x 10^-19J to get joules. Once you have joules, use the equation E = (hc)/(wavelength) to receive wa...
- Wed Oct 16, 2019 3:23 am
- Forum: Properties of Light
- Topic: Relationships
- Replies: 2
- Views: 118
Re: Relationships
Yup, you're right. In the equation c= (frequency)(wavelength), frequency and wavelength are inversely proportional because their product is a constant, the speed of light. If frequency were to increase, then wavelength would have to decrease. In the next equation E = hv, energy is equal to frequency...
- Wed Oct 16, 2019 3:20 am
- Forum: Properties of Light
- Topic: Question 1A.5
- Replies: 4
- Views: 210
Re: Question 1A.5
Yup, that would mean the least to greatest amount of energy. In terms of wavelengths and frequencies, the photons with the least amount of energy would have the longest wavelengths/lowest frequency. The photons with the greatest amount of energy would have the shortest wavelength/highest frequency b...
- Wed Oct 16, 2019 3:16 am
- Forum: Properties of Light
- Topic: Electromagnetic Radiation
- Replies: 3
- Views: 182
Re: Electromagnetic Radiation
Following the EM spectrum, the photons would be ordered microwaves, visible light, ultraviolet radiation, x-rays, gamma rays from lowest to highest energy. This is because microwaves has the lowest frequency/longest wavelengths, which corresponds to lower energy. The higher the frequency/shorter the...
- Wed Oct 16, 2019 3:13 am
- Forum: Properties of Light
- Topic: 1A.11
- Replies: 2
- Views: 136
Re: 1A.11
The Balmer and Lyman series are grouped the way they are because of how they were discovered. The Balmer series corresponds to the emission lines emitted when a hydrogen atom returns to the energy level with principle quantum number 2. The Lyman series corresponds to the lower energy level with prin...
- Mon Oct 14, 2019 12:21 pm
- Forum: Properties of Electrons
- Topic: Calculating amount of energy needed to remove an electron
- Replies: 1
- Views: 158
Calculating amount of energy needed to remove an electron
How much energy is required to remove an electron from one sodium atom, given that light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Would I just use the conversion 1 mol = 6.02x10^23 atoms to convert the w...
- Wed Oct 09, 2019 2:02 am
- Forum: Empirical & Molecular Formulas
- Topic: Molecular formula
- Replies: 6
- Views: 2810
Re: Molecular formula
If you were given the total molecular mass and the mass percentage composition of each element, you can assume that you have 100. g of the substance and convert each percentage to its respective mass (ie converting 45.6% carbon to 45.6 g of carbon). Next, you would find the moles of each element by ...
- Wed Oct 09, 2019 1:55 am
- Forum: Properties of Light
- Topic: Light and our Skin
- Replies: 2
- Views: 219
Re: Light and our Skin
I don't believe UV radiation is harmful to our skin because of its potential to eject electrons. Because our skin is not made of metal and we are not in a vacuum, the concept of the photoelectric effect does not apply to our skin. UV radiation is harmful to us because the rays have enough energy to ...
- Wed Oct 09, 2019 1:50 am
- Forum: Properties of Light
- Topic: Hw Question 1A.9
- Replies: 5
- Views: 578
Re: Hw Question 1A.9
To find the wavelength and frequency of the photon in this question, it is best to start from what you know. You know the energy of the photon, so the only equation we can use in this instance would be E(photon) = vh, where v is the frequency in Hertz and h is Planck's constant. Rearrange the equati...
- Wed Oct 09, 2019 1:43 am
- Forum: Properties of Light
- Topic: Question 1A.5
- Replies: 3
- Views: 170
Re: Question 1A.5
You are correct. Shorter wavelength/higher frequency corresponds to higher energy, while longer wavelength/lower frequency corresponds to lower energy. This is because a particle is able to complete more oscillations in a 1 second interval.
- Wed Oct 09, 2019 1:35 am
- Forum: Properties of Light
- Topic: Light intensity
- Replies: 6
- Views: 174
Re: Light intensity
If light is at a higher intensity, the amplitude of the wave is simply higher. The frequency and wavelength remains the same. One way you could achieve a higher intensity light is by increasing the number of photons. However, this change did not impact the photoelectric experiment because one single...
- Wed Oct 09, 2019 1:32 am
- Forum: Properties of Light
- Topic: Question 1A.3 c
- Replies: 5
- Views: 338
Re: Question 1A.3 c
According to the equation c = λv, where c is a constant representing the speed of light in a vacuum, λ (wavelength) and v (frequency) are indirectly proportional. If frequency were to increase, wavelength must decrease. In this question, the frequency decreases, so wavelength must therefore increase...
- Tue Oct 01, 2019 1:09 pm
- Forum: Empirical & Molecular Formulas
- Topic: Homework Problem E.9c
- Replies: 5
- Views: 201
Re: Homework Problem E.9c
How do you find the formula for magnesium sulfate heptahydrate? To find the formula for magnesium sulfate hydrate, you must know the ions that magnesium and sulfate form. Magnesium always forms Mg2+ and sulfate is (SO4)2-. Therefore, magnesium sulfate is MgSO4. Hepta- is a prefix meaning 7, so ther...
- Tue Oct 01, 2019 1:05 pm
- Forum: Empirical & Molecular Formulas
- Topic: Percentage Yield
- Replies: 3
- Views: 124
Re: Homework Problem M.1
The percentage yield is the actual yield, which is the 25.2g of hydrazine, divided by the theoretical yield, which is the maximum product that can be produced, then multiplied by 100 to obtain a percent. To find the theoretical yield, you would need to convert the grams of reactant, ammonia, to mole...
- Tue Oct 01, 2019 12:58 pm
- Forum: Empirical & Molecular Formulas
- Topic: Rounding [ENDORSED]
- Replies: 12
- Views: 746
Re: Rounding [ENDORSED]
Rounding in chemistry usually occurs at the very end of your calculations in order to prevent rounding differences from accumulating.