Search found 61 matches
- Sat Mar 16, 2019 12:02 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: K'
- Replies: 4
- Views: 511
Re: K'
It is a usual rate to understand in order to solve using the pre-equilibrium method!
- Sun Mar 10, 2019 11:08 pm
- Forum: Second Order Reactions
- Topic: Temperature
- Replies: 6
- Views: 604
Re: Temperature
The rate constant can change according to temperature. If you increase the temperature, you increase the rate.
- Sun Mar 10, 2019 11:05 pm
- Forum: Second Order Reactions
- Topic: Slope
- Replies: 2
- Views: 268
Re: Slope
Like stated above, the slope is based off the change in concentration over time. As time increases, the concentration decreases. In a first order reaction, the y-axis is ln[A] thus as A decreases as time increases, ln[A] will also decrease. Thus creating a negative slope. However for a second order,...
- Sun Mar 10, 2019 10:59 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: molecularity
- Replies: 8
- Views: 806
Re: molecularity
The molecularity is based on the number of particles/molecules that will collide simultaneously as this reaction occurs. It's based on the number of species.
- Sun Mar 10, 2019 10:58 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Reactions with Multiple Reactants
- Replies: 3
- Views: 370
Re: Reactions with Multiple Reactants
Yes, this is so we can do simply calculations. Therefore, we assume that there's excess/large quantity of the other reactants such that their concentration is insignificant to the rate.
- Sun Mar 10, 2019 10:56 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: rate determining
- Replies: 3
- Views: 288
Re: rate determining
As stated above it would be the slowest step because it would add the most to the reaction rate.
- Sat Feb 23, 2019 7:49 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cell Diagram
- Replies: 6
- Views: 537
Re: Galvanic Cell Diagram
I believe its good have an understanding of how it works, how the charges flow, and be able to visualize what the cell looks like based on the cell diagram given.
- Sat Feb 23, 2019 7:47 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Faradays Constant
- Replies: 4
- Views: 543
Re: Faradays Constant
Faradays constant is the "F" in the equation. It's units will help cancel out the others to leave you with units of energy!
- Sat Feb 23, 2019 7:45 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: -charge x E = Wmax
- Replies: 2
- Views: 298
Re: -charge x E = Wmax
Its negative because the system is doing work. Had the system have work done on it, it would have a positive charge.
- Sat Feb 23, 2019 7:44 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 14.9 6th Edition
- Replies: 2
- Views: 277
Re: 14.9 6th Edition
You'll be able to find the number of moles transferred by balancing the equation through separating the half reactions.
- Sat Feb 23, 2019 7:41 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidating/Reducing AGENTS
- Replies: 6
- Views: 713
Re: Oxidating/Reducing AGENTS
The oxidizing agent was reduced and it oxidizes the reducing agent. Vice versa. The oxidizing agent gain in electron which means it took a electron from the reducing agent.
- Mon Feb 11, 2019 9:16 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: why is H negative when calculating S?
- Replies: 4
- Views: 436
Re: why is H negative when calculating S?
Freezing is an exothermic process, thus the transfer of energy is released.
- Mon Feb 11, 2019 9:15 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: DeltaS=kBlnW
- Replies: 3
- Views: 617
Re: DeltaS=kBlnW
This equation is used to calculate residual entropy on a microscopic level. It refers to W, (the number of micro-states it may take)^ # of particles. Kb is Boltzmann's constant given on the formula sheet.
- Mon Feb 11, 2019 9:13 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Cv/Cp versus R
- Replies: 4
- Views: 460
Re: Cv/Cp versus R
R is used in isothermal reactions whereas 3/2R and 5/2R are used in place of Cp or Cv where there is a temperature change.
- Mon Feb 11, 2019 9:11 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Ideal Behavior
- Replies: 3
- Views: 390
Re: Ideal Behavior
chloewinnett1L wrote:I was going to ask the same thing, should we always take "ideal conditions" to mean 1 mol of gas and pressure=1 atm?
If not stated otherwise, then such assumption would be sufficient.
- Mon Feb 11, 2019 9:09 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy Change in reversible reaction
- Replies: 3
- Views: 399
Re: Entropy Change in reversible reaction
The total entropy change does not equal 0 under such conditions. It is the change in internal energy that equals 0.
- Mon Feb 11, 2019 9:08 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Converting Celsius to Kelvin
- Replies: 7
- Views: 666
Re: Converting Celsius to Kelvin
273 K should be fine. It also helps if you look at the overall sig figs required for the specific condition.
- Mon Feb 11, 2019 9:07 am
- Forum: Calculating Work of Expansion
- Topic: Reversible vs Irreversible
- Replies: 10
- Views: 965
Re: Reversible vs Irreversible
Usually it would be told whether or not the system is reversible or irreversible.
- Sun Feb 03, 2019 5:02 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: 1st law of thermodynamics
- Replies: 7
- Views: 578
Re: 1st law of thermodynamics
Since all matter can not be created nor destroyed, all the internal energy of an isolated system will remain constant.
- Sun Feb 03, 2019 5:01 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: 3 methods for enthalpy calculation
- Replies: 10
- Views: 1913
Re: 3 methods for enthalpy calculation
The most effective method would be based on the conditions given. The only difference is the accuracy and reliance of the method.
- Sun Feb 03, 2019 5:00 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated System
- Replies: 5
- Views: 790
Re: Isolated System
ΔU is zero because it can't be heated and no material can be added. Therefore, there's no work nor is there q.
- Sun Feb 03, 2019 4:57 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: open system
- Replies: 8
- Views: 1308
Re: open system
The constant pressure exerted onto the beaker is the atmospheric pressure which is much larger than any pressure that the system exerts on the surroundings.
- Fri Jan 25, 2019 6:52 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Solving bond enthalpies
- Replies: 3
- Views: 258
Re: Solving bond enthalpies
When you break a bond, you require energy. (+) On the other hand, when a bond is formed, energy is released. (-)
- Fri Jan 25, 2019 6:51 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 5
- Views: 361
Re: Hess's Law
Hess's Law is taught in Chem 14B like stated above. It's used to calculate the total enthalpy of the rxn using the separate enthalpies of rxns in between.
- Fri Jan 25, 2019 6:50 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 3 Methods
- Replies: 3
- Views: 232
Re: 3 Methods
The general reason is because the bond enthalpies for molecules that are not diatomic are averages depending on the different molecules they occur in.
- Sat Jan 19, 2019 5:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ka vs. Kb
- Replies: 12
- Views: 4564
Re: Ka vs. Kb
Ka is used for acids and Kb is used for bases. You can also determine the Ka based on knowing the Kb and vice versa.
- Sat Jan 19, 2019 5:51 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: exothermic/endothermic
- Replies: 3
- Views: 491
Re: exothermic/endothermic
You can determine it based on the sign of delta h (enthalpy). You can also tell from the description of the reaction; whether or not energy is required or released.
- Sat Jan 19, 2019 5:49 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert Gas added
- Replies: 4
- Views: 289
Re: Inert Gas added
The inert gas will not have any effect on the equilibrium system. Since it doesn't react, it won't change.
- Thu Jan 10, 2019 1:51 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Finding K in 5I.7
- Replies: 3
- Views: 238
Re: Finding K in 5I.7
From what I know,we would be expected to know the method taught during lecture and in the modules for now.
- Thu Jan 10, 2019 1:50 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: The relationship between Kc and K
- Replies: 2
- Views: 246
Re: The relationship between Kc and K
Its not that Kc is greater or less than K, but it is greater or less than Q. K is used in terms of equilibrium. On the other hand Q is used at any time during the reaction. When the mols of reactants are greater than those of products, the reaction proceed forward in order to create more products fo...
- Thu Jan 10, 2019 1:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Giving Qc or Qp when asked for Q
- Replies: 5
- Views: 595
Re: Giving Qc or Qp when asked for Q
This depends on the given information. If you are given units of concentration then use Qc (if they give you the grams and liters this applies too) but if you're given units of pressure then use Qp!
- Sat Dec 08, 2018 10:04 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: Atoms that don't affect pH
- Replies: 3
- Views: 508
Re: Atoms that don't affect pH
Atoms that don't contribute to the creation of OH- or H3O+ are spectator ions and will not affect the pH.
- Thu Nov 29, 2018 1:49 pm
- Forum: Biological Examples
- Topic: acids
- Replies: 5
- Views: 398
Re: acids
The digestive system contains buffers which will increase the pH of acids to a safe level. On the other hand when acids enter cuts they burn since cellular/atomic level destruction breakdown occurs. There are no protective buffers in these locations that can dilute the pH acidity level to neutral nu...
- Thu Nov 29, 2018 1:47 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Cis and Trans
- Replies: 10
- Views: 961
Re: Cis and Trans
There's no definite answer to which is better. The preferred version depends on the purpose of the molecule. The situation at hand will determine the more desired form between the two.
- Thu Nov 29, 2018 1:44 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination Number
- Replies: 10
- Views: 891
Re: Coordination Number
The coordination number of transition metals can be calculated by knowing the overall charges of the compound and the individual charges of non-metals in the compound. The charges of all atoms within the compound should add up to the overall charge of the compound.
- Sat Nov 24, 2018 10:51 am
- Forum: Hybridization
- Topic: S-Character Bond Angle Trend
- Replies: 3
- Views: 242
Re: S-Character Bond Angle Trend
With greater regions of electron density comes smaller bond angles.
- Sat Nov 24, 2018 10:46 am
- Forum: Hybridization
- Topic: double bonds
- Replies: 14
- Views: 1128
Re: double bonds
Double bonds consist of one pi and one sigma bond because the orientation of a double bond consists of a both a side to side overlap as well as a end-to-end overlap. When you continue to add bonds, you'll add another pi bond since there is now another side-to-side overlap.
- Sat Nov 24, 2018 10:42 am
- Forum: Hybridization
- Topic: Octet Expansion and d-Orbitals
- Replies: 8
- Views: 780
Re: Octet Expansion and d-Orbitals
So is any element in the first 3 groups without a d-orbital in its shell unable to fulfill the octet rule? Under my current understanding, I believe any element in the first three groups don't have to meet the octet rule of maximum 8 electrons, it can exceed the octet rule since it has access to th...
- Sat Nov 24, 2018 10:39 am
- Forum: Hybridization
- Topic: Writing out Hybridization
- Replies: 8
- Views: 556
Re: Writing out Hybridization
Either order works. The book tends to write it with the d-orbital first, however you can write it afterwards as well.
- Sat Nov 24, 2018 10:37 am
- Forum: Hybridization
- Topic: determining shape from given information
- Replies: 3
- Views: 362
Re: determining shape from given information
No, hybridization only tells us the number of regions of electron density around the central atom. It doesn't tell us the specific bonds/pairs around it. (bonded or lone)
- Sat Nov 24, 2018 10:36 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Drawing Structures on Test
- Replies: 11
- Views: 940
Re: Drawing Structures on Test
According to what was stated in class, you'll only be really expected to draw the lewis structure and determine the name of the shape.
- Sat Nov 24, 2018 10:33 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sixth Edition. Question 4.109
- Replies: 4
- Views: 1063
Re: Sixth Edition. Question 4.109
Great question! Though not drawn, it is assumed that there are two lone pairs attached to oxygen to complete the octet. Therefore there's a total of 4 regions of electron density. The lone pairs repel each other and the bonded pairs thus creating a bent shape. This has the bond angle of 109.5.
- Sat Nov 24, 2018 10:30 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs on the Central Atom
- Replies: 5
- Views: 504
Re: Lone Pairs on the Central Atom
Lone pairs do a play a major role in determining the shape. The repulsion of lone pairs is even stronger than those of bonded pairs. It will push the bonded pairs away. However, the actual shape does not take lone pairs in consideration. You name the shape based off the location of bonded pairs that...
- Mon Nov 12, 2018 10:40 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond angles
- Replies: 3
- Views: 326
Re: Bond angles
You would know the bond angles from knowing the shape based on electron repulsion. The number of pairs around the central atom will repel one another creating semi-symmetric bond angles. This is based on the angle that allows the electrons to be as far as possible away from others.
- Mon Nov 12, 2018 10:37 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: How do you utilize the VSEPR model?
- Replies: 4
- Views: 445
Re: How do you utilize the VSEPR model?
The VSEPR theory is a method in order to identify the shape of a molecule. This is determined based off the number of lone pairs and bonded pairs on the central atom. These characteristics are linked to a specific shape identified by the VSEPR Theory.
- Mon Nov 12, 2018 10:35 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Chapter 4 Homework Number 1
- Replies: 6
- Views: 434
Re: Chapter 4 Homework Number 1
The bond angles will change according to the presence of electrons. This is due to the concept of electron repulsion (negatives repel negatives).
- Mon Nov 05, 2018 9:49 am
- Forum: Electronegativity
- Topic: Periodic Trends
- Replies: 10
- Views: 1191
Re: Periodic Trends
Without considering exceptions, I like to think the trend from least to greatest.
For size you have increasing going left and down.
and almost anything else (ionization energy, electronegativity, etc.) is increasing going up and right.
For size you have increasing going left and down.
and almost anything else (ionization energy, electronegativity, etc.) is increasing going up and right.
- Mon Nov 05, 2018 9:45 am
- Forum: Resonance Structures
- Topic: Resonance with formal charge
- Replies: 6
- Views: 589
Re: Resonance with formal charge
The resonance of a structure will not change the FC.
- Mon Nov 05, 2018 9:44 am
- Forum: Octet Exceptions
- Topic: Radicals
- Replies: 16
- Views: 1661
Re: Radicals
The radical is placed with the atom based on the formal charge. Remember that we want a FC closer to 0.
- Mon Nov 05, 2018 9:41 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge Equation
- Replies: 13
- Views: 3370
Re: Formal Charge Equation
An easier way to look at the equation is:
FC = Valence electrons - (line + dots)
lines being the bonds
dots being the individuals in lone pairs
FC = Valence electrons - (line + dots)
lines being the bonds
dots being the individuals in lone pairs
- Fri Oct 26, 2018 1:03 pm
- Forum: Lewis Structures
- Topic: Lewis Dot Order
- Replies: 10
- Views: 1197
Re: Lewis Dot Order
Like stated above, there is no particular order; however, you should consider symmetry.
- Fri Oct 26, 2018 1:00 pm
- Forum: Trends in The Periodic Table
- Topic: Removing 2nd Electron
- Replies: 9
- Views: 725
Re: Removing 2nd Electron
The second ionization energy is always greater than the first since the pull of the positive protons int he nucleus is much greater.
- Fri Oct 26, 2018 12:58 pm
- Forum: Trends in The Periodic Table
- Topic: Atomic, Covalent, and Ionic Radius
- Replies: 5
- Views: 1059
Re: Atomic, Covalent, and Ionic Radius
haleyervin7 wrote:How will we know if something is ionically or covalently bonded?
In a covelant bond, you would share electrons. This often occurs between two non-metals due to their high ionization energy.
On the other, ionic bonds are between a metal and a nonmetal where there is a transfer of electrons instead.
- Sat Oct 20, 2018 11:13 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Lyman, Balmer, Pascal
- Replies: 10
- Views: 1399
Re: Lyman, Balmer, Pascal
Lynsea_Southwick_3F wrote:Would n never equal 4 or anything more then 3?
There are energy levels greater than 4. Electrons are not limited to only 4 states of energy.
- Sat Oct 20, 2018 11:10 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: HW 2.19
- Replies: 3
- Views: 365
Re: HW 2.19
Your calculations are correct! The issue may be in the Textbook version you're using. It may not be corresponding (in edition) with your solution manual. Based off the 6th edition, (b) asks about the 6-d subshell and (c) 3-p subshell. These situations align with the solution manual you are using. Ho...
- Thu Oct 11, 2018 3:10 pm
- Forum: Properties of Light
- Topic: Photoelectric effect
- Replies: 4
- Views: 203
Re: Photoelectric effect
The energy of each photon does not necessarily have to be greater. It needs to reach a certain level of energy to remove an electron. That fence it needs to climb over would be the threshold or work energy.
- Thu Oct 11, 2018 3:08 pm
- Forum: Properties of Light
- Topic: Balmer series vs Lyman series
- Replies: 4
- Views: 210
Re: Balmer series vs Lyman series
That would be based on which energy level the electron is currently at and where it's going to go. The Lyman series is based on Ultraviolet light which entitles a larger change in energy from level 1. On the other hand, the Balmer series are frequency and wavelengths relevant to Visible light and le...
- Thu Oct 11, 2018 3:04 pm
- Forum: Properties of Light
- Topic: Why Short Wavelengths Can Eject e-
- Replies: 6
- Views: 915
Re: Why Short Wavelengths Can Eject e-
It's a general concept that as frequency increases, wavelength decreases. Frequency is inversely proportional to energy per photon. In the case of attempting to emit electrons from metal surfaces, you would need a specific frequency corresponding to energy. Rather than looking at the wavelength, its...
- Mon Oct 01, 2018 8:52 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Study Module Post-assessment Question
- Replies: 5
- Views: 339
Re: Study Module Post-assessment Question
I am confused on this problem as well. I'm unsure of what the initial and final volumes are. I used the 15L as the initial volume and when it came to the final volume I was not sure whether to use the 0.02L or 0.250L. The final volume would be .250 ml since it's what you're transferring and attempt...
- Mon Oct 01, 2018 8:35 pm
- Forum: Limiting Reactant Calculations
- Topic: Percent yield
- Replies: 10
- Views: 939
Re: Percent yield
The actual percent yield would be given like how molar mass of a compound would need to be given in order to further advance calculations. :)
- Mon Oct 01, 2018 8:34 pm
- Forum: SI Units, Unit Conversions
- Topic: Naming Compounds
- Replies: 8
- Views: 533
Re: Naming Compounds
With calcium sulfide and it's chemical notation, you could recognize the bond between the two elements. The -ide contributes to the fact that it is indeed an ionic compound. Calcium has a charge of +2 and sulfur has a charge of -2; therefore, the notation would be CaS. The quickest way to figure it ...