## Search found 60 matches

Wed Mar 13, 2019 2:48 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E˚ vs E
Replies: 13
Views: 3069

### Re: E˚ vs E

E˚ refers to the cell potential of a cell at standard conditions (25 degrees celsius, 1 M and 1 atm) and so it is a constant value that is given and will not change. E refers to the cell potential of a cell at any time, whether or not it's at standard conditions.
Wed Mar 13, 2019 2:44 pm
Forum: Second Order Reactions
Topic: Temperature
Replies: 6
Views: 276

### Re: Temperature

Temperature should only affect the rate constant
Wed Mar 13, 2019 2:43 pm
Forum: General Rate Laws
Topic: slow step
Replies: 11
Views: 686

### Re: slow step

It will typically be told as the slow step or if it's in a proposed mechanism, I think we are expected to deduce which is the slow step based on the experimentally determined rate law.
Wed Mar 13, 2019 2:41 pm
Forum: Balancing Redox Reactions
Topic: Oxidation vs Reduction Half Rxn
Replies: 9
Views: 494

### Re: Oxidation vs Reduction Half Rxn

an oxidation reaction when you're writing out the balanced charges and elements should have the electrons on the products side as you are losing the electrons (LEO) and the reduction reaction should have the electrons on the reactant side since they are gaining electrons (GER).
Wed Mar 13, 2019 2:40 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Log version vs ln Version
Replies: 7
Views: 358

### Re: Log version vs ln Version

Both versions give you the right answer. However, on the equation sheet, the log version is a constant over n, so you have to keep in mind that the constant given can only be used if the reaction is taking place at 25 Celsius.
Wed Mar 13, 2019 2:38 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst
Replies: 14
Views: 491

### Re: Nernst

yes, the total n is referring to the amount of electrons transferred in the balanced redox reaction.
Wed Mar 13, 2019 2:36 pm
Forum: Balancing Redox Reactions
Topic: Balancing basic redox reactions
Replies: 7
Views: 538

### Re: Balancing basic redox reactions

I like to balance it first like an acidic reaction with H+ and then to remove the H+, add OH- on both sides to neutralize the H+ to H2O. That way, you'll have H2O and OH-.
Wed Mar 13, 2019 2:35 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: k & K
Replies: 18
Views: 1007

### Re: k & K

k is the rate constant so it's basically an indicator of how fast the reaction will happen. K is the equilibrium constant that tells you the ratio of products to reactant concentrations when the reaction is at equilibrium. Based on the relationship between k and K, we can determine that the forward ...
Wed Mar 13, 2019 2:33 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 6
Views: 238

### Re: Catalysts

The catalyst will be needed for the reaction to occur and therefore will be present before the reaction takes place. It will then get made again (or not used up) so the catalyst will then be present before the reaction takes place and after the reaction takes place.
Wed Mar 13, 2019 2:31 pm
Forum: Zero Order Reactions
Topic: Zero Order Reaction
Replies: 5
Views: 438

### Re: Zero Order Reaction

I think this was mentioned in class but zero order reactions occur when the concenctration is super high that there is barely a difference in concentration respect to time.
Tue Mar 12, 2019 11:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram
Replies: 6
Views: 276

### Re: Cell diagram

There has to be a solid in the cell to transfer the electrons. Therefore, if the reaction itself doesn't have a solid or metal we add carbon or platinum.
Tue Mar 12, 2019 11:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Increasing reducing power
Replies: 4
Views: 654

### Re: Increasing reducing power

So reducing power refers to the strength of the ion/substance as a reducing agent. The ion/substance that is being oxidized is also the reducing agent. Therefore, the more the ion/substance wants to be oxidized the stronger it is as a reducing agent or reducing power. We can determine the oxidizatio...
Mon Feb 18, 2019 7:48 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Internal energy (U) of an isolated system
Replies: 17
Views: 1258

### Re: Internal energy (U) of an isolated system

The internal energy of the system would not change as an isolated system doesn't exchange energy or matter with it's surroundings and based off the conservation of energy theory, if energy isn't used or exchanged, the energy will stay constant.
Mon Feb 18, 2019 7:47 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: reversible and irreversible processes
Replies: 9
Views: 569

### Re: reversible and irreversible processes

Reversible processes are when the external pressure is changing in minuscule amounts and so the volume is changing in minuscule amounts and can return to it's original state. Irreversible processes have a constant external pressure so once it expands/compresses to a certain volume, it will stay the ...
Mon Feb 18, 2019 7:44 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Delta H given
Replies: 2
Views: 360

### Re: Delta H given

It is because the definition of delta H is the change in enthalpy of a reaction under constant pressure. Therefore, you know when delta H is given, the reaction took place under constant pressure.
Mon Feb 18, 2019 7:43 pm
Forum: Calculating Work of Expansion
Topic: Units for R
Replies: 10
Views: 727

### Re: Units for R

There are various ways in which one can use the constant R and so there are various units for the constant. For example, in the PV=nRT equation, one side has atm*L and the other as mol*K*R, and so to cancel so they equal each other, R has the unit and value of 0.08206 atm*L/mol*K. However, for work,...
Mon Feb 18, 2019 7:39 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Extensive Property
Replies: 3
Views: 418

### Re: Extensive Property

An extensive property is something where the value changes based on the amount of something. For example, mass changes based on how much of a sample you have. Similarly, heat capacity on it's own changes based on how much of the sample you have. 10 g of a substance may take 10 joules to raise it by ...
Mon Feb 18, 2019 7:37 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: state functions and properties
Replies: 11
Views: 3253

### Re: state functions and properties

A state function is something where the path doesn't matter, only the initial and final state. The reason it is so important is that since the path doesn't matter, you can subtract, add, multiply, and divid state functions as necessary.
Thu Jan 31, 2019 1:29 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Work
Replies: 4
Views: 280

### Re: Work

When we look at work, the negative sign is just used to indicate which side of the system is doing work, not necessarily the amount of work. We would look at work's magnitude so we would disregard the sign change when comparing the two different systems.
Thu Jan 31, 2019 1:25 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Work Question
Replies: 4
Views: 211

### Re: Work Question

Although the correlation is very similar, work refers to how the energy could be used/transferred and energy is the ability to do work. So just because a system has a lot of energy, it doesn't mean that work is being done because nothing may change or that energy isn't being used.
Thu Jan 31, 2019 1:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: understanding calculating reaction enthalpy
Replies: 2
Views: 178

### Re: understanding calculating reaction enthalpy

I would say yes that the enthalpy of a reaction refers to the heat of the reaction since all enthalpy of a reaction is, is the change in enthalpy or heat of a reaction and so that correlates to the heat given off/absorbed by the reaction. As for which of the 3 methods is best, it really depends on w...
Thu Jan 24, 2019 5:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pKa vs. pH
Replies: 15
Views: 2308

### Re: pKa vs. pH

pKa stands for -log of Ka and pH stands for -log of Hydronium ions. Consider the p as a function rather than a symbol. All the p does is mathematically change the value, similar to a negative sign or derivative. Ka is the dissociation of an acid or the equilibrium constant for the acid whereas H is ...
Thu Jan 24, 2019 5:50 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy and States
Replies: 8
Views: 343

### Re: Enthalpy and States

Yup! Enthalpy is related to states and the enthalpy change of one state will be different than the enthalpy change of a different state.
Thu Jan 24, 2019 5:47 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Le Chateliers Priniciple
Replies: 9
Views: 502

### Re: Le Chateliers Priniciple

Only if the volume is decreased/increase. If you're adding an inert gas that would technically change pressure but would not affect the equilibrium/ shift the equation.
Fri Jan 18, 2019 11:18 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Weak Acids and Bases
Replies: 6
Views: 286

### Re: Weak Acids and Bases

If the concentration of the hydronium ion is smaller then 10^-7, say 10^-9, the pH calculated if you use that will give you 9 - a basic solution. However, you have to keep in mind that there is hydronium ions in the water already and that concentration is 10^-7. So if you add the concentrations of t...
Fri Jan 18, 2019 11:10 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Negative pH
Replies: 12
Views: 822

### Re: Negative pH

Yes, pH can be negative since pH is just the -log of the concentration of hydronium. pH can also exceed 14.
Fri Jan 18, 2019 11:08 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: sigfigs for acids/bases
Replies: 3
Views: 181

### Re: sigfigs for acids/bases

For pH, the significant figures matter AFTER the decimal. So if the concentration of Hydronium ions is .0136 mol/L , 3 sig figs. The pH would be 1.866, 3 sig figs after the decimal.
Thu Jan 10, 2019 3:57 pm
Forum: Ideal Gases
Topic: Units
Replies: 19
Views: 498

### Re: Units

The units should be in Kelvin as the universal gas constant, R is in Kelvin. To find convert from Celsius to Kelvin just add 273.15.
Thu Jan 10, 2019 3:55 pm
Forum: Ideal Gases
Topic: Equilibrium Favoring
Replies: 4
Views: 98

### Re: Equilibrium Favoring

When analyzing the equilibrium constant equation, we can see that the concentration of products is over the concentration of reactants. Therefore, the bigger the number, the larger the ratio between products to reactants is, or the more product is compared to the reactants. So, when the equilibrium ...
Thu Jan 10, 2019 3:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pure solids and liquids in eq. constants [ENDORSED]
Replies: 4
Views: 631

### Re: Pure solids and liquids in eq. constants[ENDORSED]

For pure solids, you can't find the concentration because it is a solid. For liquids, typically the liquid will be a solvent and therefore, there's a lot of it. If the reaction takes place with some molecules of the solvent, the amount of molecules changed is so insignificant that you can regard it ...
Fri Dec 07, 2018 9:26 pm
Forum: Calculating the pH of Salt Solutions
Topic: pH sig figs
Replies: 4
Views: 429

### Re: pH sig figs

On Dr.Lavelle's sig fig worksheet, he said to count the sig figs after the decimal for pH, so I suggest you go with that.
Fri Dec 07, 2018 9:15 pm
Forum: Amphoteric Compounds
Topic: Oxalate bidentate
Replies: 4
Views: 176

### Re: Oxalate bidentate

It is called bidentate because the oxalate is able to bind to the metal twice with it's two oxygens that have electron pairs to spare.
Fri Dec 07, 2018 9:06 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: structure of SO2 and SO3
Replies: 2
Views: 151

### Re: structure of SO2 and SO3

I may be wrong but i believe that the structure of SO2 and SO3 are like that because they have resonance and resonance makes a structure a lot stronger and stable so resonance is preferred!
Wed Nov 28, 2018 9:26 pm
Forum: Sigma & Pi Bonds
Topic: Sigma vs. Pi
Replies: 11
Views: 888

### Re: Sigma vs. Pi

A single bond will only have 1 sigma bond. The very first bond made is a sigma bond and each additional bond is a pi bond. I like to count the number of bonds and save one for sigma and the rest as pi. So amount of pi bonds are # of bonds - 1.
Wed Nov 28, 2018 9:14 pm
Forum: Naming
Topic: Naming Coordination Compounds
Replies: 9
Views: 557

### Re: Naming Coordination Compounds

I think we will have to know common ligands such as ammine, chloro, and cyano.
Wed Nov 28, 2018 9:09 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: AXE formula
Replies: 32
Views: 6597

### Re: AXE formula

Yes. With the AXE formula you can deduce what shape and bond angle the molecule will have based on charts and tables.
Wed Nov 28, 2018 9:06 pm
Forum: Hybridization
Topic: Sp3d or dsp3
Replies: 22
Views: 935

### Re: Sp3d or dsp3

Order doesn't matter but some prefer writing it dsp3 since it shows that the d orbital is utilized however sp3d is in order of utilization.
Wed Nov 28, 2018 9:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.21
Replies: 2
Views: 157

### Re: 4.21

Nitrogen can not have 5 bonds because it doesn't have a d-orbital. Only elements in Group 3 plus have d-orbitals they can utilize for more than 4 bonds.
Wed Nov 28, 2018 8:50 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Boiling Point
Replies: 3
Views: 831

### Re: Boiling Point

Yes. The stronger the IMFs are the harder it is to break the forces holding the molecules together. To boil something is to turn that substance to liquid to gas and that requires breaking the forces therefore, it takes more energy to break the stronger IMFs. In this case, energy is in the form of he...
Fri Nov 16, 2018 8:50 pm
Forum: Dipole Moments
Topic: Dipole Moments
Replies: 6
Views: 266

### Re: Dipole Moments

Dipole moments are formed when atoms don't "share" electrons fairly so the more electronegative atom would pull the electrons to their side creating a temporary charge shift, the dipole moment.
Fri Nov 16, 2018 8:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AX3E2 Shape
Replies: 6
Views: 511

### Re: AX3E2 Shape

So AX3E2's steric number is 5 and so that shape would be trigonal bipyramidal but since you remove two atoms and have two lone pairs in it's place, the final shape would be t-shaped.
Fri Nov 16, 2018 8:45 pm
Forum: Hybridization
Topic: Sigma and Pi
Replies: 5
Views: 256

### Re: Sigma and Pi

Sigma bonds are first because without sigma bonds, pi bonds wouldn't form. You can only have one sigma bond because the orbitals have to be the right spin and attraction to hybridize into sigma bonds and the pi are the other orbital hybridizations.
Fri Nov 09, 2018 2:17 pm
Forum: Dipole Moments
Topic: Classification of Van der Waals
Replies: 2
Views: 132

### Re: Classification of Van der Waals

All molecules have in some way shape or form Van der Waals forces. These forces are typically weak but when there are many, it can be strong and prevalent.
Fri Nov 09, 2018 2:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Tetrahedral molecules
Replies: 4
Views: 180

### Re: Tetrahedral molecules

Yes, tetrahedral molecules should have a bond angle of 109.5
Fri Nov 09, 2018 2:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Naming the molecular shape
Replies: 4
Views: 292

### Re: Naming the molecular shape

Lone pairs matter! The steric number is the amount of lone pairs and bonds the central atom has and so the steric number might be the same for multiple molecules but the shape of the molecule could be very different depending on the amount of lone pairs the atom has. For example, H2O has a steric nu...
Fri Nov 02, 2018 3:48 pm
Forum: Lewis Structures
Topic: Expanded octets
Replies: 6
Views: 363

### Re: Expanded octets

Elements after period 3 can have an expanded octet because of the additional d orbital they have. Typically, Phosphorus or Sulfur are the elements that do expand their octet.
Fri Nov 02, 2018 3:46 pm
Forum: Octet Exceptions
Topic: The center atom
Replies: 20
Views: 1306

### Re: The center atom

Typically, you would choose the element that has the lowest ionization energy as the middle and in this case, it is oxygen. Also, Chlorine typically only forms one bond so it wouldn't make sense to have Chlorine in the middle.
Fri Nov 02, 2018 3:43 pm
Forum: Resonance Structures
Topic: Most Stable Configuration
Replies: 11
Views: 551

### Re: Most Stable Configuration

It is when the atoms are closest to the formal charge of 0.
Fri Oct 26, 2018 8:22 pm
Forum: Ionic & Covalent Bonds
Topic: Electron Configuratin
Replies: 5
Views: 223

### Re: Electron Configuratin

We could eventually remove the electrons from the d and f orbitals but if you notice the shell number for the d and f orbitals, they're either 1 or 2 shells before the s and p orbitals. When you remove an electron, you take from the outermost shell since they're the easiest to be removed therefore, ...
Fri Oct 26, 2018 8:19 pm
Forum: Ionic & Covalent Bonds
Topic: Ionization Energy vs. Electronegativity
Replies: 5
Views: 250

### Re: Ionization Energy vs. Electronegativity

Ionization energy is how much energy is required to remove an electron but electonegativity is how attracted the atom is to gaining an electron. Most cases, the higher electronegativity the higher the ionization energy since they want to gain an electron, not lose an electron. Therefore, it'll be ha...
Fri Oct 26, 2018 8:16 pm
Forum: Lewis Structures
Topic: Lewis Structures vs. Line Structures
Replies: 2
Views: 124

### Re: Lewis Structures vs. Line Structures

I think we probably will be using lines in the future since it's a faster way of representing larger molecules, but the Lewis Structure allows you to see resonance and lone pairs more clearly so you can later determine the shapes of the molecules.
Fri Oct 19, 2018 2:54 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: converting moles to grams
Replies: 3
Views: 520

### Re: converting moles to grams

Yes! I think using dimensional analysis is very important when solving problems like these. Make sure that the units cancel out in the end to get what you want and make sure you're using correct values for each.
Fri Oct 19, 2018 2:53 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: How to Find the Number of Orbitals
Replies: 3
Views: 164

### Re: How to Find the Number of Orbitals

the letter ml is used to denote the amount of subshells in an orbital. Typically, the amount of subshells in an orbital is from l,l-1..0..-l.
Fri Oct 19, 2018 2:49 pm
Forum: Photoelectric Effect
Topic: Equation units
Replies: 4
Views: 215

### Re: Equation units

kg since the measurement of SI unit , Joules, is kgm^2/s^2 so we use kg
Fri Oct 12, 2018 3:29 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: molar masses on the test
Replies: 7
Views: 517

### Re: molar masses on the test

You'd typically will have to solve for molar mass which you can do by analyzing the molecule and seeing how many of each element there is, and referencing the periodic table, you can solve for molar mass.
Fri Oct 12, 2018 3:27 pm
Forum: Properties of Electrons
Topic: Atomic spectra
Replies: 5
Views: 247

### Re: Atomic spectra

So each element has different amount of varying orbital energy levels. Hydrogen's orbital energy levels are different from Oxygen's and when electrons transition from one orbital energy to another, depending on the element, the release of energy is different. The releases of energy are in the form o...
Fri Oct 12, 2018 3:24 pm
Forum: Properties of Light
Topic: Threshold Energy
Replies: 11
Views: 393

### Re: Threshold Energy

The threshold energy is the amount of energy required to bump an electron out of the metal plate that the light is hitting. It's the minimum amount of energy to rip the electron out of it's shell.
Fri Oct 12, 2018 3:21 pm
Forum: SI Units, Unit Conversions
Topic: Should Significant Figures be affected by constants?
Replies: 10
Views: 455

### Re: Should Significant Figures be affected by constants?

Constants do not affect significant figures since significant figures are a sense of how precise something is. Constants are known to be very precise and would have no affect on the final calculation for significant figures since it's already known to be precise.
Fri Oct 12, 2018 3:19 pm
Forum: Empirical & Molecular Formulas
Topic: Mass Percent Composition
Replies: 7
Views: 593

### Re: Mass Percent Composition

It should add up to 100% since mass can not be created nor destroyed and what mass percent composition is stating is just how much the particular element weighs in the whole compound, or it is a percentage of the total mass and so percentages should always add up to 100%.
Fri Oct 12, 2018 3:16 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reagent
Replies: 10
Views: 965

### Re: Limiting Reagent

I think the best way to figure out limiting reagent for any amount of reagents is figuring out the amount of moles of each reagent. Then, using the coefficients of the balanced equation, figure out how many moles of the product each reagent will get you if the rest of the reagents were in excess. Fi...