Search found 102 matches
- Sat Mar 14, 2020 2:00 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Instantaneous rate of change
- Replies: 3
- Views: 328
Re: Instantaneous rate of change
The instantaneous rate law has a negative because the amount of reactant decreases as the reaction takes place.
- Sat Mar 14, 2020 1:50 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts
- Replies: 5
- Views: 351
Re: Catalysts
It basically means the catalyst is not broken down into new molecules during the reaction.
- Sat Mar 14, 2020 1:46 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Order reaction
- Replies: 4
- Views: 371
Re: Order reaction
You can also look at the units of the k constant if it is given to determine the order.
- Sat Mar 14, 2020 1:44 am
- Forum: First Order Reactions
- Topic: size
- Replies: 6
- Views: 491
Re: size
Smaller particles have more surface area, which allow for the possibility of more collisions and increase the rate.
- Sat Mar 14, 2020 1:38 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Temperature and Kinetics
- Replies: 3
- Views: 250
Re: Temperature and Kinetics
If we increase temperature, molecules start to move faster, as we've learned when talking about phase changes, so higher temperatures garner faster moving molecules and more collisions per second.
- Sat Mar 14, 2020 1:36 am
- Forum: Balancing Redox Reactions
- Topic: QD3 Midterm
- Replies: 5
- Views: 423
Re: QD3 Midterm
Why would it be -1 exactly?
- Sat Mar 14, 2020 1:35 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Collision theory
- Replies: 2
- Views: 168
Re: Collision theory
There aren't any equations we learned that cover it, so if it is, I'm guessing it'll be a short concept question. Just know that molecules must collide with the right orientation to form a reaction.
- Sat Mar 14, 2020 1:33 am
- Forum: General Rate Laws
- Topic: Natural Log Rate Order
- Replies: 4
- Views: 335
Re: Natural Log Rate Order
In a first order reaction, the plot of the natural log over time must be a straight line with a slope of -k.
- Sat Mar 14, 2020 1:32 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Endgame 1a
- Replies: 5
- Views: 490
Re: Endgame 1a
Since cells flow from anode to cathode, it makes sense that the side with the lower concentration of cations will oxidize and the higher concentration will be reduced until both sides are balanced.
- Sat Mar 14, 2020 1:27 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Calculations using Nernst Eq.
- Replies: 2
- Views: 243
Re: Calculations using Nernst Eq.
When you make both sides exponents of e, the ln in front of the concentrations cancel and you can solve the other side of the equation to get your answer.
- Sat Mar 14, 2020 1:15 am
- Forum: Balancing Redox Reactions
- Topic: OH vs H
- Replies: 12
- Views: 871
Re: OH vs H
If it's a basic solution, there's a trick that usually works. First balance the H+ by placing H2O on the opposite side, then balance the original side by adding twice the molecules of H2O, and finally add the doubles coefficient of OH to the other side to balance the additional atoms you added. The ...
- Sat Mar 14, 2020 1:04 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts
- Replies: 2
- Views: 213
Re: Catalysts
If you compare the graphs of a reaction with and without the catalyst, it will show that the reaction with a catalyst didn't have to input as much energy to continue.
- Wed Feb 26, 2020 2:28 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Which one is Product? Cathode or Anode?
- Replies: 5
- Views: 449
Re: Which one is Product? Cathode or Anode?
In the cathode, we are adding electrons, which means that the aqueous cations are becoming solid molecules, which makes sense if the cathode is where products build.
- Wed Feb 26, 2020 2:24 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.5 part A
- Replies: 1
- Views: 170
Re: 6N.5 part A
When a question has to do with ph and/or concentration of H+ ions, we can use log instead of ln. The 2.303 is 1/log(e) which we have to use when switching from ln to log.
- Wed Feb 26, 2020 2:20 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: nernst 2
- Replies: 3
- Views: 276
Re: nernst 2
The units can be written as V or J/C. It might read confusing, but just know they're the same.
- Wed Feb 26, 2020 2:18 pm
- Forum: Balancing Redox Reactions
- Topic: Help on 6L.7 part a
- Replies: 2
- Views: 243
Re: Help on 6L.7 part a
It is based on the equations they give us in the SRP table. You want Ag to cancel since it's not in the original equation, so if you flip the first half reaction, the Ag cancels on each side and you get the original products.
- Wed Feb 26, 2020 2:11 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Strength of a reducing agent
- Replies: 3
- Views: 256
Re: Strength of a reducing agent
The closer an element is to the bottom left of the periodic table, the more electronegative it is, therefore the stronger reducing agent it is.
- Sun Feb 23, 2020 1:29 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: cathode gaining mass
- Replies: 2
- Views: 219
Re: cathode gaining mass
Yes, the aqueous ions turn solid in reduction.
- Sun Feb 23, 2020 1:15 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.5 D.
- Replies: 7
- Views: 529
Re: 6L.5 D.
Just take each of the products, and see where you can place electrons and how many (on reactants side or products) in order to change Au+ into each product. Write each change as a separate equation.
- Sun Feb 23, 2020 1:11 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Le Chatelier’s Principle
- Replies: 11
- Views: 663
Re: Le Chatelier’s Principle
We are still dealing with concentrations like Al and Al3+ or Zn and Zn2+. Therefore, the same principles we learned in the equilibrium unit apply here. If there's too much concentration of one of these ions, the equilibrium will shift to satisfy LeChatelier's.
- Wed Feb 19, 2020 2:38 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Question 1 on Midterm
- Replies: 7
- Views: 533
Re: Question 1 on Midterm
If there's less reactant (NO) then there's less matter available to make product (NO2), this is why when the reaction shifts to the left due to Le Chatelier's Principle, the equation must balance at a lower partial pressure on both sides.
- Wed Feb 19, 2020 2:34 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sign of delta G
- Replies: 9
- Views: 569
Re: Sign of delta G
I agree, it depends on if they give you concentrations (use K vs Q) or information to find enthalpy and temperature (use G).
- Fri Feb 14, 2020 2:38 pm
- Forum: Phase Changes & Related Calculations
- Topic: Equation Choice
- Replies: 5
- Views: 523
Re: Equation Choice
Remember that if the phase change involves the atoms becoming more free and moving faster (i.e. solid to liquid, liquid to gas) the process is endothermic because the system is gaining heat and energy, meaning the q value is positive. The opposite is true for exothermic processes.
- Fri Feb 14, 2020 2:35 pm
- Forum: Ideal Gases
- Topic: ideal gas
- Replies: 5
- Views: 340
Re: ideal gas
Ideal gases are highly unlikely to occur in the natural world, but are useful for calculations in class and theory.
- Fri Feb 14, 2020 2:33 pm
- Forum: Ideal Gases
- Topic: pv=nrt
- Replies: 19
- Views: 1102
Re: pv=nrt
Yes, just use 273.15K for temperature and 1atm for pressure.
- Fri Feb 14, 2020 2:32 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure and Moles
- Replies: 7
- Views: 412
Re: Pressure and Moles
Add up the coefficients of the products, add up the coefficients of the reactants, then subtract to find the total change in moles for your equation.
- Fri Feb 14, 2020 2:30 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy equation
- Replies: 3
- Views: 276
Re: Entropy equation
This equation is usually used to calculate isothermal reversible processes.
- Sat Feb 08, 2020 1:37 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: 4D 3)
- Replies: 1
- Views: 92
Re: 4D 3)
You divide by the moles of CO because the question is asking for the internal energy change per 1.00 mole of CO.
- Sat Feb 08, 2020 1:35 am
- Forum: Phase Changes & Related Calculations
- Topic: Homework Problem 4C.13
- Replies: 3
- Views: 166
Re: Homework Problem 4C.13
To go from 0 degrees ice to 45 degrees liquid water, we must first go from 0 degrees ice to 0 degrees liquid water, which required an enthalpy of formation calculation. We can then use mCdeltaT to find the heat necessary to go from liquid water at 0 to the final temperature.
- Sat Feb 08, 2020 1:31 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hf and Hc
- Replies: 3
- Views: 121
Re: Hf and Hc
Hc just means it is the enthalpy of combustion, so there must be oxygen in the reactants.
- Sat Feb 08, 2020 1:29 am
- Forum: Phase Changes & Related Calculations
- Topic: 4C.13 phase change
- Replies: 2
- Views: 147
Re: 4C.13 phase change
The n delta h represents the Heat of fusion of the ice cube as it melts to a liquid and the mCdeltaT is the heat needed to go from 0 degree liquid to the final temperature. Think of it as the graph we went over in class with the steps of alternating horizontal and diagonal lines.
- Sat Feb 08, 2020 1:19 am
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Microstates and Entropy
- Replies: 1
- Views: 43
Re: Microstates and Entropy
You can use the micro states to find degeneracy by using the W=#^n equation, and then you can use degeneracy to calculate change in entropy with the delta S=kB*lnW equation.
- Fri Jan 31, 2020 2:48 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy Unit
- Replies: 6
- Views: 162
Re: Enthalpy Unit
Usually, we add or subtract other values to find delta H, so unless the problem specifically says to use kJ/mol, you can keep it in the units given for the other values of for example, q. Just make sure you are consistent throughout the equation.
- Fri Jan 31, 2020 2:43 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Boltzmann Equation
- Replies: 2
- Views: 130
Re: Boltzmann Equation
You can derive from the ideal gas law a variation equation where PV=NkBT, where the Boltzmann constant is kB and ratio of R over kB should be equal to Avogadro's constant.
- Fri Jan 31, 2020 2:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Test 1 # 4
- Replies: 10
- Views: 312
Re: Test 1 # 4
You add 273 to the 27 to get temperature in 300 degrees Kelvin, and make sure the correct Rydberg constant is used so the units Kelvin, Liters, and atm cancel.
- Fri Jan 31, 2020 2:30 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Math Resources
- Replies: 8
- Views: 230
Re: Math Resources
Yes, these are on his website under math assistance. Just click on Integration rules with application to chemistry.
- Fri Jan 31, 2020 2:28 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Degeneracy
- Replies: 9
- Views: 320
Re: Degeneracy
Degeneracy can be used to describe systems when the systems are of different states, such as solid, liquid, or gas, but equal in energy levels.
- Sun Jan 26, 2020 11:22 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Using Bond Enthalpies
- Replies: 2
- Views: 85
Re: Using Bond Enthalpies
It's the same as the ice table when we either subtracted x or added x, depending on whether it was a product or a reactant. The same applies here, we just look if that molecule is being broken down, or created, and put the corresponding positive or negative sign.
- Sun Jan 26, 2020 11:19 am
- Forum: Phase Changes & Related Calculations
- Topic: thermochemistry vs thermodynamics
- Replies: 2
- Views: 74
Re: thermochemistry vs thermodynamics
Thermochemistry is just a branch of thermodynamics that involves the heat given off or absorbed during chemical reactions.
- Sun Jan 26, 2020 11:16 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: state functions
- Replies: 4
- Views: 127
Re: state functions
State functions are important in thermochemistry because enthalpy, entropy, Gibbs free energy, etc. are all state functions, which is what allows us to add and subtract heat in the equations.
- Sun Jan 26, 2020 11:12 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Negative Square Root solving an ICE box
- Replies: 13
- Views: 485
Re: Negative Square Root solving an ICE box
When this happens to me, it's because I usually forget to square the b inside the square root, which leads to a negative inside. You should not get a negative value inside the square root.
- Sun Jan 26, 2020 11:11 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Irreversible Expansion
- Replies: 4
- Views: 249
Re: Irreversible Expansion
The difference between irreversible and reversible expansion is that in irreversible, the reaction does not remain in thermodynamic equilibrium.
- Fri Jan 17, 2020 4:18 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Strong or weak acid?
- Replies: 5
- Views: 1125
Re: Strong or weak acid?
Usually H with any of the halogens is a strong acid such as HCl, HI, HBr, and H2SO4. Also for strong bases, they'll usually have OH at the end like LiOH, NaOH, or Ba(OH)2.
- Fri Jan 17, 2020 4:14 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Value of Kw
- Replies: 6
- Views: 126
Re: Value of Kw
Since we haven't gone over any problems where we need to know Kw at a temperature other than 25 degrees Celsius, I don't think there will be any on the test. However, if both Kb and Ka are given you can find it.
- Fri Jan 17, 2020 4:10 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Temperature Change
- Replies: 9
- Views: 561
Re: Temperature Change
Think of heat as a reactant in endothermic reactions. When heat is added, its like the reactant side becomes overwhelmed, so the system needs to tip to the other side (products) to balance at equilibrium.
- Fri Jan 17, 2020 4:08 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: ICE table
- Replies: 11
- Views: 330
Re: ICE table
You should use an ice table in both cases, the only difference is for weak acid and bases, the K is less than 10^-3 which means that the [number-x ] concentration can just be calculated as [number] to save time.
- Fri Jan 17, 2020 4:04 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc & Kp
- Replies: 12
- Views: 281
Re: Kc & Kp
Kc is when the numbers given are concentrations while Kp is when the values are partial pressures.
- Thu Jan 09, 2020 4:33 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Why is K unitless?
- Replies: 10
- Views: 562
Re: Why is K unitless?
When we set up the equation for K, it is K= [M]/[M], as in a concentration over another concentration. So just think of it as canceling out the units M in the fraction, leaving you with a unitless number.
- Thu Jan 09, 2020 4:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reactants and Products Affecting Equilibrium
- Replies: 2
- Views: 157
Re: Reactants and Products Affecting Equilibrium
^The above comment is true because if you add more of a substance on the reactants side, this increases the likelihood of the correct reactants colliding with the correct geometry to create a chemical reaction, which means the forward reaction would be favored.
- Thu Jan 09, 2020 4:23 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q vs K
- Replies: 7
- Views: 226
Re: Q vs K
If Q is less than K at some time during the reaction, then compared to the equilibrium concentrations [R] > [P] and the forward reaction is favored, and vice versa.
- Thu Jan 09, 2020 4:20 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: confused about ice table
- Replies: 5
- Views: 134
Re: confused about ice table
ICE stands for the Initial concentrations, the Change in each, and the Equilibrium concentrations. So lets say a gas that is a reactant in the equation has a concentration of 1M, and in the balanced equation has a coefficient of 2, you'd have 1-2x in the final equilibrium row. Once you have calculat...
- Thu Jan 09, 2020 3:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: solid/liquid
- Replies: 7
- Views: 179
Re: solid/liquid
Yes, solids and gases have no significant effect on the equilibrium reaction, so only include the gases and aqueous solutions.
- Thu Dec 05, 2019 12:20 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate
- Replies: 2
- Views: 111
Re: Polydentate
Elaborating on what the previous comment said, CN can’t take on 2 ligands because of the electron repulsion between the ligands if the bonds are too close to each other.
- Thu Dec 05, 2019 12:14 pm
- Forum: Naming
- Topic: amine or ammine
- Replies: 2
- Views: 118
Re: amine or ammine
Ammine has to do with ligands and coordination compounds while amine has to do with derivatives of ammonia like NH3 or NH4
- Thu Dec 05, 2019 12:10 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: London disperson
- Replies: 6
- Views: 266
Re: London disperson
London dispersion is the same as Van der waals but not the same as dipole dipole. Dr.Lavelle said he prefers induced dipole induced dipole when describing London forces but it doesn’t matter all are correct.
- Thu Dec 05, 2019 12:05 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Oxolate Chelate
- Replies: 6
- Views: 334
Re: Oxolate Chelate
Chelates are polydentates so 2 or more bonding sites.
- Thu Dec 05, 2019 12:03 pm
- Forum: Bronsted Acids & Bases
- Topic: Names of acids
- Replies: 1
- Views: 149
Re: Names of acids
Just memorize the most common ones like HCl H2SO4 H3PO4 that we’ve learned and know how to find of its a strong acid or a weak acid.
- Tue Dec 03, 2019 5:03 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Resonance and Formal Charge
- Replies: 4
- Views: 360
Re: Resonance and Formal Charge
The formal charges differ because in some structures, the atoms have double bonds, single bonds, or Lone pairs. The major contributor is the one closest to a 0 total formal charge, and if that isn't possible usually the central atom should have 0 charge unless it violates the octet rule.
- Tue Dec 03, 2019 4:54 pm
- Forum: Bronsted Acids & Bases
- Topic: Self-test J.1A/B
- Replies: 3
- Views: 265
Re: Self-test J.1A/B
For a, KCl has neither H+ ions nor OH- ions, so it is neither. HClO and HF both donate H+ ions, so they're acids and Ca(OH)2 donates an OH- ion, so it's a base.
- Tue Dec 03, 2019 4:49 pm
- Forum: Lewis Acids & Bases
- Topic: charges of transitional metals
- Replies: 3
- Views: 185
Re: charges of transitional metals
For example, for iron in Fe2O3, since there is a neutral charge of 0, we know there is a 3 x -2 = -6 charge for oxygen, therefore the irons must total a +6 charge and when you divide by 2 atoms, you get +3 as the formal charge for each iron atom. We write this as iron(III)oxide.
- Tue Dec 03, 2019 4:34 pm
- Forum: Sigma & Pi Bonds
- Topic: Unhybridized orbitals.
- Replies: 3
- Views: 353
Re: Unhybridized orbitals.
Pi bonds don't allow rotation and sigma bonds do. Also, one single bond has a sigma bond while a double bond has one sigma and a pi bond.
- Tue Dec 03, 2019 2:58 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Latin names
- Replies: 2
- Views: 160
Re: Latin names
There is a link on Professor Lavelle's website that says "naming coordination compounds." I recommend looking at that page and just getting familiar with a few concepts.
- Fri Nov 29, 2019 7:03 pm
- Forum: Lewis Acids & Bases
- Topic: 6A.13
- Replies: 7
- Views: 338
Re: 6A.13
The positive charge means it is missing electrons in the full shell, making it an electron acceptor.
- Fri Nov 29, 2019 6:42 pm
- Forum: Bronsted Acids & Bases
- Topic: Trichloroacetic acid vs acetic acid
- Replies: 2
- Views: 118
Re: Trichloroacetic acid vs acetic acid
Trichloroacetic acid is just acetic acid with 3 Cl atoms instead of 3 H. Therefore, the Cl atoms have a stronger pull on the bonds of the carboxyl group, loosening the OH bond and making H+ions more likely to dissociate.
- Fri Nov 29, 2019 6:36 pm
- Forum: Bronsted Acids & Bases
- Topic: Bronsted base
- Replies: 3
- Views: 81
Re: Bronsted base
It can be kind of confusing because NH3 has H atoms which makes us think of H+ ions and acids; however, in water, it gains H+ ions and becomes NH4, making it a bronzed base.
- Fri Nov 29, 2019 6:34 pm
- Forum: Bronsted Acids & Bases
- Topic: Acids and Bases
- Replies: 3
- Views: 207
Re: Acids and Bases
Usually acids have H+ ions that will dissociate, but in order to be 100% sure about any polar or non polar characteristics, draw the structure.
- Fri Nov 29, 2019 6:32 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg
- Replies: 4
- Views: 322
Re: Rydberg
Just think of it in relation to the nucleus. If an electron is emitted aka going away, it's a negative energy value. If it is being absorbed and coming closer, it is positive.
- Wed Nov 20, 2019 5:57 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles in Square Pyramidal and T-Shaped
- Replies: 4
- Views: 264
Re: Bond Angles in Square Pyramidal and T-Shaped
T shaped has a less than 90 degree angle for all of the angles between the bonds that form the actual T, but the 2 lone pairs at the top that repel each other are what forms the 120 degree angle with the bottom atom of the T.
- Wed Nov 20, 2019 5:44 pm
- Forum: General Science Questions
- Topic: Test 2: IMF
- Replies: 4
- Views: 220
Re: Test 2: IMF
Just to give a general ballpark for the values, here's the list he gave us in lecture,
Ion-Ion = -250kJ/mol
Ion-dipole = -15kJ/mol
Dipole-dipole = -2kJ/mol
Dipole-induced dipole = -kJ/mol
Ion-Ion = -250kJ/mol
Ion-dipole = -15kJ/mol
Dipole-dipole = -2kJ/mol
Dipole-induced dipole = -kJ/mol
- Wed Nov 20, 2019 5:42 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: T-Shaped ??
- Replies: 9
- Views: 735
Re: T-Shaped ??
AX2E is bent v shaped and its bond angles are 120 each, separated symmetrically.
- Wed Nov 20, 2019 5:38 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate
- Replies: 2
- Views: 191
Re: Polydentate
I'd say yes draw it out to be sure the formal charges are correct and the number of lone pairs on the central atom are correct. I doubt there will be a test question where part a doesn't involve drawing the shape anyway.
- Wed Nov 20, 2019 5:32 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: XA2E2
- Replies: 9
- Views: 414
Re: XA2E2
The molecule is called bent (v shaped) and looks very similar to a tetrahedral except for one of the electron lone pairs takes the place of where the third bonded molecule would have gone, which is why the angles are slightly less than 109.5.
- Sat Nov 16, 2019 10:03 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Subscript on E
- Replies: 5
- Views: 287
Re: Subscript on E
It shouldn't matter, just like how when writing the charge of a molecule in a lewis structure, you can write "-" on the top right of the brackets or "1-"
- Sat Nov 16, 2019 9:59 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 8
- Views: 298
Re: Bond Angles
You don't need to memorize every possible exception, just know that in some cases like ammonia and water, the bond angles are slightly less than 109.5 because of the strength of the repulsion of the lone pairs.
- Sat Nov 16, 2019 9:56 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2E 11 b)
- Replies: 4
- Views: 187
Re: 2E 11 b)
Also, if we added double bonds, the Iodine atom would have a +2 charge since it would have 5 bonds around it, and we try to make the central atom have as close to a formal charge of 0 as possible.
- Sat Nov 16, 2019 9:53 pm
- Forum: Bond Lengths & Energies
- Topic: Lone pairs
- Replies: 7
- Views: 600
Re: Lone pairs
You determine whether a lone pair is axial or equatorial by looking at the bond angles and making sure the lone pair has enough room to evenly repel the other bonded electrons.
- Sat Nov 16, 2019 9:48 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR Model
- Replies: 2
- Views: 185
Re: VSEPR Model
To solve this,, just count the amount of electrons - 34 if you add the negative charge - then continue doing a lewis structure like normal, then go down the charge and find which example fits the model with the same number regions of electron densities.
- Sun Nov 10, 2019 11:20 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 and Melting Points
- Replies: 7
- Views: 487
Re: Boiling and Melting Points
The boiling point of H2S is -60 degrees C while the boiling point of H2O is 100 degrees C. These molecules are very similar in structure, but H2O is harder to break down because the bonds are stronger.
- Sun Nov 10, 2019 11:12 pm
- Forum: Dipole Moments
- Topic: Dipole moment units
- Replies: 4
- Views: 229
Re: Dipole moment units
Usually they are written in Debye which are 1 x 10^-18 C*m. It is just more applicable for working with small numbers.
- Sun Nov 10, 2019 11:10 pm
- Forum: Octet Exceptions
- Topic: Octet exception
- Replies: 14
- Views: 1205
Re: Octet exception
Some typical exceptions are S, P, and Cl.
- Sun Nov 10, 2019 11:08 pm
- Forum: Resonance Structures
- Topic: octet v. expanded octet
- Replies: 5
- Views: 313
Re: octet v. expanded octet
You don't physically draw the Lewis structure of an expanded octet bigger it just looks the same as a regular structure except for there are more bonds around the central atom.
- Sun Nov 10, 2019 11:05 pm
- Forum: Coordinate Covalent Bonds
- Topic: Coordinate Covalent Bond
- Replies: 3
- Views: 250
Re: Coordinate Covalent Bond
A coordinate covalent bond is a covalent bond where both of the electrons being shared come from one atom.
- Mon Nov 04, 2019 7:55 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: initial and final variables
- Replies: 4
- Views: 270
Re: initial and final variables
Honestly, I always just label each number with an M1 or M2 or V1 or V2 in between the print just so I don't get confused, but you can write it out and find the missing value.
- Mon Nov 04, 2019 5:52 pm
- Forum: Lewis Structures
- Topic: Electron Configuration & Formal Charge for Cu
- Replies: 4
- Views: 160
Re: Electron Configuration & Formal Charge for Cu
my TA said to just always write the electron configuration as if it had no charge, and depending on if the charge is positive or negative, add or subtract electrons from the end. So in this case, 3d10 is to the left of 4s1. We take off one electron in the 4s because it is the rightmost one and then ...
- Mon Nov 04, 2019 5:48 pm
- Forum: Lewis Structures
- Topic: How do I know when to use a double bond?
- Replies: 7
- Views: 960
Re: How do I know when to use a double bond?
Regarding double bonds in molecules with resonance, he said to compute the formal charges for each atom to find the lowest state possible in each of the possible resonance structures. So just use the equation, FC=V-(L+S/2).
- Mon Nov 04, 2019 5:45 pm
- Forum: *Shrodinger Equation
- Topic: Shrodinger equation
- Replies: 7
- Views: 510
Re: Shrodinger equation
It wasn't on the equation sheet for the first test on fundamentals even though other quantum equations were on it, so I doubt it'll be on the midterm unless he changed the equation sheet. However, just in case, spend like 5 minutes on it to get a general understanding.
- Mon Nov 04, 2019 5:41 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Atomic Orbitals in Terms of Probability
- Replies: 6
- Views: 396
Re: Atomic Orbitals in Terms of Probability
This just means that there is a probability that the electron will be following the path of the orbital described in its l value. However, we cannot be 100% accurate in predicting the exact location of an electron as they don't follow rigid paths, which is why we use probability.
- Wed Oct 30, 2019 5:26 pm
- Forum: Octet Exceptions
- Topic: Radicals
- Replies: 9
- Views: 321
Re: Radicals
An example of a radical would be CH3 which we did in class. C has 4 valence electrons and each of the 3 hydrogens have 1, giving the molecule a total of 7 valence electrons. This makes the molecule highly radioactive and it only exists for a short time because it will try to bond with another CH3 mo...
- Wed Oct 30, 2019 5:22 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity
- Replies: 8
- Views: 239
Re: Electron Affinity
Electron affinity is also known as the likelihood of an atom gaining an electron. Therefore, it increases as you move to the right because the valence she’ll becomes closer to being full as the atom becomes more desperate to gain that last electron that will fill its shell. It increases as you move ...
- Wed Oct 30, 2019 5:17 pm
- Forum: Ionic & Covalent Bonds
- Topic: ionic vs covalent bonds
- Replies: 6
- Views: 250
Re: ionic vs covalent bonds
Yes, and also you can look at how far the elements are from each other on the periodic table. If there is a cation in the far left that is bonded with an anion in the far left, this means there is a great electronegativity difference and it is an ionic bond.
- Wed Oct 30, 2019 5:14 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic Bonds
- Replies: 6
- Views: 322
Re: Ionic Bonds
Usually ionic bonds are between cations, which are to the left of the periodic table, and anions, which are toward the right. This creates a difference in electronegativity which is greater than 2, therefore their stronger bond due to the attraction between opposite charges.
- Wed Oct 30, 2019 5:10 pm
- Forum: Lewis Structures
- Topic: Valence Electrons from Periodic Table
- Replies: 10
- Views: 638
Re: Valence Electrons from Periodic Table
It does correspond to the group but make sure you skip over the transition metals in the middle when looking at elements toward the right. For example, Boron has 3 valence electrons, not 13.
- Mon Oct 21, 2019 8:44 pm
- Forum: Trends in The Periodic Table
- Topic: 2nd Ionization Energy
- Replies: 7
- Views: 349
Re: 2nd Ionization Energy
The first ionization energy is how much energy is needed to remove an electron from a neutral atom. The second ionization energy is how much energy is needed to remove an electron from a positively charged atom, meaning it has already lost an electron. It would take more energy to remove a second on...
- Mon Oct 21, 2019 8:41 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Cr and Cu Exceptions
- Replies: 2
- Views: 94
Re: Cr and Cu Exceptions
The elements Cr and Cu are exceptions because their configuration, if you write it out, has 4 and 9 electrons in the 3d orbital. However, since these are one electron away from forming half shells (5 electrons in the 3d orbital) and full shells (10 electrons in the 3d orbital), an electron is pulled...
- Mon Oct 21, 2019 8:34 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity Trends
- Replies: 5
- Views: 580
Re: Electron Affinity Trends
The electron affinity increases as you move left to right because the rightmost elements have an almost full valence electron shell, making them more desperate to gain another electron to fill the outer shell. Electron affinity decreases moving down because the electrons are in farther shells to the...
- Mon Oct 21, 2019 8:25 pm
- Forum: Trends in The Periodic Table
- Topic: Atomic Radius
- Replies: 3
- Views: 111
Re: Atomic Radius
The atomic radius is half the diameter of a neutral atom while the ionic radius pertains to the radius of the cation and anion in an ionic bond. They tend to be larger for anions and smaller for cations.
- Mon Oct 21, 2019 8:18 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: S-, P-, S-, and F- Orbitals
- Replies: 3
- Views: 183
Re: S-, P-, S-, and F- Orbitals
Think of orbitals as surrounding shells that the electrons move really fast through. For example, for the s orbital, the electrons MOST LIKELY can be found traveling around the nucleus following a spherical path. The same goes for p d and f orbitals. However, we can't know 100% where an electron wil...
- Thu Oct 03, 2019 11:44 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Determining Molar Mass
- Replies: 19
- Views: 586
Re: Determining Molar Mass
If there is a possibility to be more accurate, honestly just take the extra time to do it because sometimes rounding can lead to drastic differences in the answer because of the small amount of substances in some problems.
- Thu Oct 03, 2019 11:39 pm
- Forum: Balancing Chemical Reactions
- Topic: H.25 Question
- Replies: 3
- Views: 254
Re: H.25 Question
There are a couple of other diatomic molecules that would be useful later. Hydrogen, Nitrogen, Oxygen, Fluorine, Iodine, Chlorine, and Bromine all have a subscript of 2 when alone.
- Thu Oct 03, 2019 11:33 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Fundamentals G5
- Replies: 3
- Views: 141
Re: Fundamentals G5
You kind of have to work backwards for this problem. You know you need 0.00215 mol Na at the end, which you need 0.001075 mol Na2CO3 since there is a ratio of 1:2. Since you are looking for volume and already have the final moles, you know you are looking for the molarity because of n=MV. The molari...