Search found 97 matches
- Sun Mar 08, 2020 3:16 pm
- Forum: Second Order Reactions
- Topic: Termolecular
- Replies: 43
- Views: 2197
Re: Termolecular
termolecular would cause third order reactions, which is when three molecules collide a the exact same time in the exact very specific orientation to generate a reaction. the possibility of this is very low, so it is a rare occurrence
- Sun Mar 08, 2020 2:30 pm
- Forum: First Order Reactions
- Topic: rate constants
- Replies: 30
- Views: 1366
Re: rate constants
yes rate constants are always positive because even when reactions slow down or reverse, the rate from product to reactant is still moving forward, making the rate constant positive.
- Sun Mar 08, 2020 2:18 pm
- Forum: First Order Reactions
- Topic: order of reaction equations
- Replies: 6
- Views: 483
Re: order of reaction equations
Although Dr. Lavelle does a lot of derivations in class, I believe he does them so we can see the correlations. I doubt we would be asked to derive the integrated rate law since practical application seems to be more the theme of his exams
- Sun Mar 08, 2020 2:10 pm
- Forum: Zero Order Reactions
- Topic: third order
- Replies: 11
- Views: 1157
Re: third order
The third order is when three molecules collide at the same time and in a certain correct orientation that causes a reaction to take place.
- Sun Mar 08, 2020 2:07 pm
- Forum: Zero Order Reactions
- Topic: Not used Half life
- Replies: 8
- Views: 914
Re: Not used Half life
the half-life of a zero-order reaction actually depends on the initial concentration and the rate constant
- Sun Mar 01, 2020 6:25 pm
- Forum: General Rate Laws
- Topic: Reaction Rates
- Replies: 5
- Views: 358
Re: Reaction Rates
reaction rates are always positive because despite the possibility of reactions slowing down, it is nevertheless moving forward still.
- Sun Mar 01, 2020 5:37 pm
- Forum: First Order Reactions
- Topic: First Order Reaction Rate
- Replies: 4
- Views: 277
Re: First Order Reaction Rate
Adriana_4F wrote:Does anyone know if this will be on Test 2?
I believe that test 2 only goes up till electrochemistry, and rate laws are part of kinetics, so I don't think rate laws will be on test 2.
- Sun Mar 01, 2020 5:36 pm
- Forum: First Order Reactions
- Topic: Order of the Reaction
- Replies: 2
- Views: 222
Re: Order of the Reaction
the order of the reaction means that the rate is proportional to the concentration of types of molecules involved in the reaction. the reactants must collide simultaneously, with enough energy and the correct orientation to make a reaction happen.
- Sun Mar 01, 2020 4:11 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: how can you tell
- Replies: 11
- Views: 746
Re: how can you tell
reactions that quickly react usually mean that it is controlled more via kinetics, while reactions that are carried out more slowly suggest that they are being controlled more via thermodynamics. this is also the reason why the terms spontaneous and nonspontaneous might be misleading,
- Sun Mar 01, 2020 4:08 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: intermediate
- Replies: 26
- Views: 1941
Re: intermediate
Intermediates ultimately get canceled out when you write out chemical equations in the full, so they will not show up in the rate law because only the initial reactants and final products have an influence on the rate law.
- Sun Feb 23, 2020 7:10 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: F
- Replies: 7
- Views: 429
Re: F
Faraday's constant is the charge in coulombs of 1 mole of electrons
- Sun Feb 23, 2020 7:08 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: how to get n in equation
- Replies: 8
- Views: 492
Re: how to get n in equation
the n in the NERNST equation is the number of electrons from the half reactions
- Sun Feb 23, 2020 6:35 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Platinum
- Replies: 4
- Views: 249
Re: Platinum
to add on to the above responses, aside from platinum, another suitable solid inert substance is graphite.
- Sun Feb 23, 2020 6:34 pm
- Forum: Balancing Redox Reactions
- Topic: Flow of electrons
- Replies: 11
- Views: 750
Re: Flow of electrons
Yes; anodes are oxidized and cathodes are reduced. Thus the flow of electrons is from oxidized substances to reduced substances.
- Sun Feb 23, 2020 6:33 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox EQs
- Replies: 10
- Views: 625
Re: Balancing Redox EQs
the reaction depends on the molecules involved; if acidic, use H+ and if acidic, use OH-
- Mon Feb 17, 2020 3:24 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Signs for Gibbs Free Energy
- Replies: 11
- Views: 649
Re: Signs for Gibbs Free Energy
A negative deltaG means that the reaction is spontaneous, and usually exothermic. A positive delta G means that the reaction is nonspontaneous, and usually endothermic.
- Mon Feb 17, 2020 3:13 pm
- Forum: Balancing Redox Reactions
- Topic: Rules for oxidation numbers
- Replies: 6
- Views: 320
Re: Rules for oxidation numbers
ions have less or more electrons than the pure substance; thus their charge is never zero
- Mon Feb 17, 2020 2:35 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation number
- Replies: 10
- Views: 727
Re: oxidation number
you can also find oxidation numbers in the context of the reactions, like when you write out the oxidation and reduction half-reactions
- Mon Feb 17, 2020 2:32 pm
- Forum: Balancing Redox Reactions
- Topic: Why do we split equations?
- Replies: 12
- Views: 745
Re: Why do we split equations?
Splitting the reactions allows you to see the intermediate molecules that would not be seen in the net reaction. Also, it allows you to identify the electron transfer more easily.
- Mon Feb 17, 2020 2:28 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Delta G
- Replies: 6
- Views: 338
Re: Delta G
also, delta G naught usually refers to the reaction in a laboratory setting, while delta G refers to reactions in a biological setting, like within the body.
- Sun Feb 09, 2020 11:51 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: Degrees of Change in Entropy
- Replies: 5
- Views: 180
Re: Degrees of Change in Entropy
also, to add on to the answers above, the degree symbol next to the delta variables indicate that they occur under lab conditions. without the degree symbol, the delta variables are typically in regards to biological conditions.
- Sun Feb 09, 2020 11:27 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Temp vs Vol
- Replies: 3
- Views: 301
Re: Temp vs Vol
Adding on to the previous answer, volume and pressure changes are temporary, so it will affect Q, but the reaction will always adjust to return to equilibrium K.
- Sun Feb 09, 2020 11:25 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Gibbs Free Energy
- Replies: 2
- Views: 207
Re: Gibbs Free Energy
There are still some cases that might differ! For example, imagine that the enthalpy value and the entropy value were both positive. If the value this would mean the (-TdeltaS) would be negative. However, if the value of enthalpy is higher than the value of -TdeltaS, overall Gibbs free energy would ...
- Sun Feb 09, 2020 11:23 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Entropy V.S Enthalpy QUestion
- Replies: 3
- Views: 371
Re: Entropy V.S Enthalpy QUestion
Not necessarily, spontaneous and nonspontaneous would have to depend on how large the values of entropy and enthalpy are compared to each other. For example, if both entropy and enthalpy were negative, it is still possible for the overall reaction to be nonspontaneous if the value of entropy multipl...
- Sun Feb 09, 2020 11:20 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Study Advice
- Replies: 73
- Views: 6753
Re: Study Advice
I really like going to Lyndon's workshops on Mondays, but to study I also rewrite my notes the day of the lecture (mainly because I have bad handwriting haha but it really helps), and doing the problems from the textbook! Also! study buddies are super helpful, even if it's just to help you stay focu...
- Sun Feb 02, 2020 5:16 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy Changes Due to Temperature
- Replies: 2
- Views: 141
Entropy Changes Due to Temperature
For entropy changes due to temperature, does it vary depending on whether or not the reaction is exothermic or endothermic? I was thinking that increasing temperature for an endothermic reaction would actually decrease the entropy of the system...
- Sun Feb 02, 2020 5:06 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: entropy?
- Replies: 4
- Views: 199
Re: entropy?
entropy is the measure of disorder in a system. the more disorderly, the more (positive) the entropy and vice versa. disorder in a system also modifies energy, so it is important to include entropy when describing a system.
- Sun Feb 02, 2020 5:04 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Value of q
- Replies: 11
- Views: 534
Re: Value of q
in a perfect system, q(system)=-q(surroundings). if we apply this to the universe as a whole (surroundings), this would be true. besides that, there are no true perfect systems.
- Sun Feb 02, 2020 4:58 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard States
- Replies: 2
- Views: 62
Re: Standard States
standard states also mean that since the molecule/element is in its most stable form, it will not undergo a change that changes enthalpy. Therefore, enthalpy of standard state molecules/elements are zero.
- Sun Feb 02, 2020 4:51 pm
- Forum: Phase Changes & Related Calculations
- Topic: phase change from liquid to vapor
- Replies: 8
- Views: 304
Re: phase change from liquid to vapor
The more kJ/mol that the phase change takes, the more energy is released. A liquid burn does not have a phase change; it is merely the water that gets heated, but has not reached the point where enough energy changes the liquid into a gas. By contrast, a steam burn, upon contact with your skin, turn...
- Sun Jan 26, 2020 5:19 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Properties
- Replies: 3
- Views: 159
Re: State Properties
Some examples of state properties are temperature, pressure, and volume.
- Sun Jan 26, 2020 5:14 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Types of Delta H
- Replies: 3
- Views: 97
Re: Types of Delta H
the unit for delta Hf is kJ/mol, but for delta Hc I believe that the units are kJ/C, in which C represents a unit uniform throughout the problem
- Sun Jan 26, 2020 5:10 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard enthalpy of solids and liquids
- Replies: 2
- Views: 57
Re: Standard enthalpy of solids and liquids
unless specified otherwise, the conditions in which the substances are in should usually use the standard enthalpies of formation
- Sun Jan 26, 2020 4:46 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard enthalpy of element in most stable form
- Replies: 5
- Views: 341
Re: Standard enthalpy of element in most stable form
from what I understand, the standard enthalpy of an element is dependent on the standard state that the element is typically found in. For example, oxygen is not typically found as just O, but it is found as O 2 . Thus, like a previous comment said above, the standard enthalpy of the element in its ...
- Sun Jan 26, 2020 4:38 pm
- Forum: Phase Changes & Related Calculations
- Topic: What is a state function?
- Replies: 3
- Views: 153
Re: What is a state function?
A state function describes the type of system the observed materials are in, and quantitatively describe the equilibrium state of said system.
- Sun Jan 19, 2020 9:55 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: temperature
- Replies: 10
- Views: 409
Re: temperature
Depending on if the reaction is exothermic or endothermic, temperature will change the equilibrium constant (K) of the reaction. Usually, unless a problem says otherwise, we can treat the reaction like it is at room temperature.
- Sun Jan 19, 2020 9:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K vs Q
- Replies: 14
- Views: 315
Re: K vs Q
K is appropriate to use when the reaction is already at equilibrium. There is only one K value for each reaction and its circumstances (temperature, pressure, etc.) Q is appropriate to use at any point in time of the reaction, and is used to compare to K.
- Sun Jan 19, 2020 9:50 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: X was ignored
- Replies: 27
- Views: 989
Re: X was ignored
the -x was ignored because the value is so small that it makes no difference to include it or not. This is called a small approximation.
- Sun Jan 19, 2020 9:41 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE Tables
- Replies: 13
- Views: 432
Re: ICE Tables
H2O isn't usually included because it is provided in excess in experiments, and is usually in liquid form. Liquid and solids are not supposed to be included in ICE tables.
- Sun Jan 19, 2020 7:50 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Acidity and Basicity
- Replies: 4
- Views: 161
Re: Acidity and Basicity
A high pH and a low pOH means that the resulting solution is basic. A low pH and a high pOH means that the resulting solution is acidic. pH and pOH values should add up to be 14.
- Fri Jan 10, 2020 9:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Le Chatelier's Principle
- Replies: 7
- Views: 279
Re: Le Chatelier's Principle
An example of Le Chatelier's would be to decrease the volume, and if there are more moles of gas on the left, then the reaction would shift to the right to accommodate for the change and vice versa.
- Fri Jan 10, 2020 5:18 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q and speed of reaction
- Replies: 5
- Views: 287
Re: Q and speed of reaction
Q is only the constant calculated from the ratio between the products and reactants at some point in time during the reaction before it reaches equilibrium. It does not actually tell us the speed at which the reaction takes place.
- Fri Jan 10, 2020 5:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Catalysts
- Replies: 7
- Views: 150
Re: Catalysts
All of the above are correct, but also, as discussed in class, it's important to add that catalysts only speed up the reaction, but the ultimate yield of the concentration will be the same as letting the reaction proceed by itself. This means that catalysts only help the reaction reach its equilibri...
- Fri Jan 10, 2020 5:01 pm
- Forum: Ideal Gases
- Topic: Chatelier’s Principle
- Replies: 8
- Views: 194
Re: Chatelier’s Principle
Le Chatelier's Principle basically means that a reaction will adapt to any changes as a response to minimize the effect of the change. This means that if pressure is increased or decreased, Le Chatelier's principle tells us that the reaction will adjust to keep K, the equilibrium constant, stable.
- Fri Jan 10, 2020 4:59 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Response of Equilibria to Change
- Replies: 3
- Views: 211
Response of Equilibria to Change
Can someone re-explain the real reason behind why reactions, upon changing the pressure, respond to minimize the effect of increasing pressure? Dr. Lavelle said in class that many of us learned the shortcut version, wherein upon increasing pressure, the reaction would go opposite the direction of th...
- Sun Dec 08, 2019 11:33 pm
- Forum: Bronsted Acids & Bases
- Topic: amphoteric
- Replies: 7
- Views: 1704
Re: amphoteric
adding on to the above replies, an example of a common amphoteric molecule is water. Water can act as either an acid or base depending on the reactions.
- Sun Dec 08, 2019 11:30 pm
- Forum: Conjugate Acids & Bases
- Topic: single arrow vs double arrow
- Replies: 2
- Views: 1975
Re: single arrow vs double arrow
Yes, double arrows typically indicate that the reaction does not completely dissociate and is reversible. Single arrows indicate that the reaction dissociates completely.
- Sun Dec 08, 2019 10:30 pm
- Forum: Lewis Acids & Bases
- Topic: Strong/Weak Acids and Bases
- Replies: 4
- Views: 480
Re: Strong/Weak Acids and Bases
I’d like to add that strong bases include group 1 hydroxides, alkaline earth metal hydroxides, and group 1 and 2 oxides.
- Sun Dec 08, 2019 10:06 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis Acids.
- Replies: 4
- Views: 1397
Re: Lewis Acids.
Lewis acids are electron acceptors, meaning they usually receive lone pairs. The molecule that is more electron deficient is typically the Lewis acid. On the other hand, Lewis bases are electron donors, so they give away lone pairs.
- Sun Dec 08, 2019 9:56 pm
- Forum: Amphoteric Compounds
- Topic: examples
- Replies: 3
- Views: 313
Re: examples
One example of an amphoteric compound is water, H2O.
Water as a base:
HCl(aq) + H2O(l) —> H3O+(aq) + Cl-(aq)
Water as an acid:
H2O(l) + NH2-(aq) —> OH-(aq) + NH3(aq)
Water as a base:
HCl(aq) + H2O(l) —> H3O+(aq) + Cl-(aq)
Water as an acid:
H2O(l) + NH2-(aq) —> OH-(aq) + NH3(aq)
- Sat Nov 30, 2019 8:23 pm
- Forum: Amphoteric Compounds
- Topic: compounds
- Replies: 5
- Views: 337
Re: compounds
An amphoteric compound can donate and/or accept protons. Amphoteric compounds have both acid and base-like properties. Some examples of amphoteric compounds are water and amino acids (which make up proteins).
- Sat Nov 30, 2019 4:23 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Value of pH
- Replies: 8
- Views: 409
Re: Value of pH
It's possible to calculate a negative pH, but in practice in a lab, negative pH can't really be tested for.
- Sat Nov 30, 2019 4:18 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: [H3O+] and [OH-]
- Replies: 3
- Views: 251
Re: [H3O+] and [OH-]
to convert between [H3O+] and [OH-], use [H3O+]=10-pHmol . L-1. pH+pOH = 14 maximum, so we can use this equation to find and convert between [H3O+] and [OH-].
- Sat Nov 30, 2019 3:11 pm
- Forum: Amphoteric Compounds
- Topic: Textbook question 6A.17
- Replies: 1
- Views: 103
Re: Textbook question 6A.17
Elements that are in and close to the diagonal line of metalloids usually make amphoteric oxides. If you look at figure 6A.7 on page 450, Bi2O3 is classified as an amphoteric oxide.
- Sat Nov 30, 2019 1:25 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Do strong acids dissociate completely in water?
- Replies: 7
- Views: 575
Re: Do strong acids dissociate completely in water?
Strong acids have a higher concentration of hydrogen ions than weak acids. This means that for strong acids, all of the hydrogen ions dissociate immediately, while weak acids dissociate more slowly.
- Sun Nov 24, 2019 5:43 pm
- Forum: Biological Examples
- Topic: Drawing biological examples
- Replies: 1
- Views: 151
Re: Drawing biological examples
I believe we'll be expected to know how to draw some of the coordination compounds for the test, but they might give us the chemical formula, since that seems to be the pattern from previous tests.
- Sun Nov 24, 2019 5:37 pm
- Forum: Biological Examples
- Topic: TMs' biological functions
- Replies: 3
- Views: 231
Re: TMs' biological functions
Chromium as an element in general is a beneficial to one's health, but doing some research after Dr. Lavelle's lecture, the best chromium supplementation is said to be chromium picolinate, which is a coordination compound.
- Sun Nov 24, 2019 5:26 pm
- Forum: Biological Examples
- Topic: cisplatin
- Replies: 6
- Views: 375
Re: cisplatin
The pros of cisplatin are that they kill cancer cells very effectively. A minor con is that cisplatin also works on healthy cells, but Dr. Lavelle mentioned that the degree at which they kill healthy cells is relatively less than the amount of cancer cells killed.
- Sun Nov 24, 2019 3:33 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Cation outside coordination sphere
- Replies: 2
- Views: 122
Re: Cation outside coordination sphere
It is possible for cations to be outside the coordinate sphere if the net charge of the coordinate sphere is negative. This would allow for positive cations to be attracted to the outside of the coordinate sphere as a whole.
- Fri Nov 22, 2019 5:39 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: transition metals
- Replies: 3
- Views: 238
Re: transition metals
Transition metals having multiple oxidation states allows them to lose electrons fairly easily when compared to the metals in group 1 and group 2. This allows them to transfer electrons more easily as well, like the previous commentator stated.
- Fri Nov 15, 2019 8:31 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: clouds of electrons
- Replies: 3
- Views: 202
Re: clouds of electrons
Only the lone and bonded pairs pertaining to the central atom are important to determining the regions of electron density in molecule shape and structure.
- Fri Nov 15, 2019 8:23 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: bent v. straight shape
- Replies: 3
- Views: 262
Re: bent v. straight shape
Bent shapes occur when the molecule has lone pairs due to electron repulsion. For ths example, then, the model with lone pairs would be the one with a bent shape.
- Fri Nov 15, 2019 8:20 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bent shape and angles
- Replies: 6
- Views: 362
Re: Bent shape and angles
If the central atom has two bonded pairs and either one or two lone pairs, this would result in the bent shape. The bond angle would be smaller if the central atom has two lone pairs because of electron repulsion.
- Fri Nov 15, 2019 8:11 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: varying VSEPRs
- Replies: 7
- Views: 433
Re: varying VSEPRs
The shape will not vary, since, even though resonance structures exist, we count single, double, and triple bonds as one grouping.
- Fri Nov 15, 2019 8:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Notation used in VSEPR
- Replies: 8
- Views: 532
Re: Notation used in VSEPR
The formula is derived from A being the central atom, X being the atoms bonded to the central atom (with the subscript being the number of atoms bonded to the central atom), and E being the number of lone pairs the central atom has.
- Fri Nov 15, 2019 8:00 pm
- Forum: Electronegativity
- Topic: water solubility
- Replies: 4
- Views: 233
Re: water solubility
If compounds have a higher electronegativity, they are more polar. Since water itself is a polar molecule, it would dissolve polar compounds well, especially compounds with higher electronegativity.
- Sun Nov 10, 2019 12:50 pm
- Forum: Dipole Moments
- Topic: BOND STRENGTH
- Replies: 4
- Views: 215
Re: BOND STRENGTH
I believe this will depend on if the molecule has any lone pairs left and the structure of the molecule. It would be better if you had a specific example in mind, too!
- Sun Nov 10, 2019 12:46 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Can polar molecules be more polar than another?
- Replies: 5
- Views: 229
Re: Can polar molecules be more polar than another?
Yes, polar molecules can be more polar than another. You can tell when you look at the difference in electronegativity of the atoms in the molecules.
- Sun Nov 10, 2019 12:35 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Lone pairs on central atom
- Replies: 3
- Views: 149
Re: Lone pairs on central atom
Yes, lone pairs affect how polar a molecule is. Take H2O for example: oxygen has two lone pairs, which makes water a polar molecule. There is a higher negative partial charge on the oxygen end, and a higher positive partial charge on the hydrogen end.
- Sun Nov 10, 2019 12:32 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarisability and Size
- Replies: 3
- Views: 212
Re: Polarisability and Size
Polarizability increases as the volume of the atoms increase. This means that polarizability typically increases down a group and decreases left to right in a period. High polarizability makes molecules have larger dispersion forces that allow them to form temporary dipoles more easily. Bonds betwee...
- Sun Nov 10, 2019 12:22 pm
- Forum: Bond Lengths & Energies
- Topic: polarizability
- Replies: 9
- Views: 291
Re: polarizability
Polarizablility increases generally when volume occupied increases. This means, as a periodic trend, it increases down a group, but decreases across a period. Polarizability determines what kinds of bonds the atom will form, which then determines the state of the molecule.
- Sat Nov 02, 2019 3:58 pm
- Forum: Electronegativity
- Topic: Electronegativity and charge
- Replies: 2
- Views: 91
Re: Electronegativity and charge
A bigger difference in electronegativity does not mean a higher charge, but any difference larger than 1.7 or 1.8 mean that ionic bonds will form. Electronegativity increases as you move left to right on a period.
- Sat Nov 02, 2019 3:51 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: formal charge
- Replies: 5
- Views: 210
Re: formal charge
Arianna Perea 3H wrote:Does FC determine where we make double bonds?
Yes, it does! The FC equation needs to know the number of paired and unpaired electrons, and the most stable structures are those with a net charge of zero. FC can determine where double bonds will be when calculated.
- Sat Nov 02, 2019 3:33 pm
- Forum: Ionic & Covalent Bonds
- Topic: AgF,AgI,AgCl
- Replies: 2
- Views: 181
Re: AgF,AgI,AgCl
Exactly! As you move down a group, covalent characteristics of a bond increases, which causes a decrease in electronegativities of the bonded atoms and a decrease in polarity. Since water is a polar molecule, it becomes harder for it to dissolve silver halides as the covalent character increases.
- Sat Nov 02, 2019 3:28 pm
- Forum: Ionic & Covalent Bonds
- Topic: Covalent Bonds
- Replies: 1
- Views: 92
Re: Covalent Bonds
Water is typically more effective when breaking ionic compounds because the ions are attracted to the polar water molecules, which break the ionic compounds apart. Water is not as effective when breaking covalent bonds because many covalent compounds are nonpolar. Since water is polar, and many cova...
- Sat Nov 02, 2019 12:01 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic/Covalent
- Replies: 6
- Views: 178
Re: Ionic/Covalent
Ionic bonds have covalent properties that depend on the polarizability of the anion and the cation's polarizing power. Ionic bonds have more covalent character when the anion is more polarizable or when the cation has high polarizing power.
- Sun Oct 27, 2019 2:34 am
- Forum: Resonance Structures
- Topic: Resonance
- Replies: 4
- Views: 308
Re: Resonance
Adding on to the replies above, make sure to always calculate the formal charge of each atom to make sure that you have arranged the best possible structure. Not all molecules with double or triple bonds will have resonant structures, so it is important to make sure.
- Sun Oct 27, 2019 2:07 am
- Forum: Ionic & Covalent Bonds
- Topic: 2A.23
- Replies: 5
- Views: 164
Re: 2A.23
a) Mg3As2
b) In2S3
c) AlH3
d) H2Te
e) BiF3
b) In2S3
c) AlH3
d) H2Te
e) BiF3
- Sun Oct 27, 2019 2:03 am
- Forum: Ionic & Covalent Bonds
- Topic: Does the Octet Rule apply to Boron?
- Replies: 14
- Views: 793
Re: Does the Octet Rule apply to Boron?
The octet rule does not apply to boron because it only has 6 electrons. It also does not apply strictly when elements are in the third period or higher. This is because of the presence of d-orbital electrons allowing for exceptions when chemically bonded.
- Sun Oct 27, 2019 1:56 am
- Forum: Ionic & Covalent Bonds
- Topic: Double bond placement
- Replies: 15
- Views: 796
Re: Double bond placement
Adding on to the poster above, the location of double and triple bonds will depend on where the octet rule can be accommodated. They cannot be replaced wherever “because of resonance,” because we must also determine if the atom has resonance structures in the first place. If there is resonance, then...
- Sun Oct 27, 2019 1:49 am
- Forum: Trends in The Periodic Table
- Topic: atomic Radii
- Replies: 11
- Views: 400
Re: atomic Radii
In line with all above answers, yes, atomic radii increases the more electrons there are. However it is important to also note that atomic radii increases not per electron, but per subshell. Each subshell will hold a certain amount of electrons, and atomic radii increases with each new subshell.
- Sat Oct 19, 2019 11:20 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Principal Quantum Number
- Replies: 3
- Views: 134
Re: Principal Quantum Number
The principle quantum number is "calculated" depending on the energy level that the electron is on. We can find it by looking at the period the element is on. As for atom excitation, I'm not too sure about that either...
- Sat Oct 19, 2019 11:14 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: 1D.13
- Replies: 2
- Views: 123
Re: 1D.13
a) when n=7, there are 7 quantum numbers: 0,1,2,3,4,5,6
b) when an electron is in a 6d-subshell there are five values of ml: -2,-1,0,1,2
c) when an electron is in a 3p-subshell, there are three values for ml: -1,0,1
d) when n=4, there are four subshells: 4s, 4p,4d, 4f
b) when an electron is in a 6d-subshell there are five values of ml: -2,-1,0,1,2
c) when an electron is in a 3p-subshell, there are three values for ml: -1,0,1
d) when n=4, there are four subshells: 4s, 4p,4d, 4f
- Sat Oct 19, 2019 2:44 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Same spin
- Replies: 10
- Views: 479
Re: Same spin
Adding on to the above comment, two electrons with the "same spin" means that they are both either spinning upward or spinning downward. Take the element carbon: the atomic number is 6, so the electron configuration would be 1s 2 2s 2 2p 2 . The 1s and 2s shells are both at the maximum occ...
- Sat Oct 19, 2019 2:39 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Coulombs's Law
- Replies: 2
- Views: 126
Re: Coulombs's Law
r as distance between two charges is more accurate. r can describe the distance between two electrons, or the distance between and electron and a proton. At your high school, your class may have calculated using r as the distance between an electron and proton (which are in the nucleus) and just cal...
- Sat Oct 19, 2019 2:36 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 4s vs. 3d
- Replies: 6
- Views: 208
Re: 4s vs. 3d
The 4s orbital actually has higher energy than the 3d orbital if the 4s orbital is occupied by electrons. So, when we write out the electron configurations, the 3d orbital goes before 4s!
- Fri Oct 11, 2019 9:52 pm
- Forum: Properties of Electrons
- Topic: where does it travel
- Replies: 2
- Views: 135
Re: where does it travel
Electrons travel the different energy levels that an atom has. They don't necessarily follow a wavelength; rather, an electron acts as both a wave and a particle.
- Fri Oct 11, 2019 9:33 pm
- Forum: Properties of Electrons
- Topic: Electron Energy Levels
- Replies: 8
- Views: 313
Re: Electron Energy Levels
The number of energy levels that an electron can jump to depends on the number of energy levels an atom of the element has. The number of energy levels an atom has depends on its placement on the periodic table.
- Fri Oct 11, 2019 9:31 pm
- Forum: Properties of Light
- Topic: Image in lecture
- Replies: 2
- Views: 97
Re: Image in lecture
In the two images he showed during the lecture, the model with the connected oscillating wave meant that the electron circulating the nucleus was at an energy level like n=3, where the level is an integer, or whole number. The model that had the disconnected wave means that it does not "work;&q...
- Fri Oct 11, 2019 2:06 pm
- Forum: Properties of Light
- Topic: Application on Microwaves
- Replies: 1
- Views: 98
Re: Application on Microwaves
Microwave ovens are dangerous because they fit about 1 kilowatt of power inside a small box. Regular microwave radiation may have less energy than 1 photon of light, but imagine concentrating a kilowatt's worth of microwave radiation into a small box. This amount of power is how food gets reheated i...
- Fri Oct 11, 2019 2:00 pm
- Forum: *Black Body Radiation
- Topic: Black Body Radiation
- Replies: 6
- Views: 375
Re: Black Body Radiation
A "black body" is a concept that is created to imagine the complete absence of color or light or anything. Professor Lavelle said that a true black does not actually exist, so black bodies are the hypotheticals we would imagine.
- Thu Oct 03, 2019 4:20 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Fundamentals E1
- Replies: 4
- Views: 237
Re: Fundamentals E1
Start by visualizing the molecules side by side, strung together! The 144 pm they give you for radius should be calculated into the diameter of the atom (so 288 pm). First, like you said, convert 1 mole of Ag into number of atoms with Avogadro's number. Next, multiply your answer by 288 pm to find o...
- Thu Oct 03, 2019 4:15 pm
- Forum: Significant Figures
- Topic: Sig Figs and Rounding
- Replies: 4
- Views: 314
Re: Sig Figs and Rounding
Typically, it's best to save rounding for the end, just so your answer is as precise as possible! ;)))) If we round in the middle steps, the answer may turn out different than intended.
- Thu Oct 03, 2019 4:11 pm
- Forum: SI Units, Unit Conversions
- Topic: Discussion Credit
- Replies: 7
- Views: 387
Re: Discussion Credit
For discussion credit, we'll be turning in 5 homework problems and do 5 posts; questions and replies both count! :))
- Mon Sep 30, 2019 11:19 pm
- Forum: SI Units, Unit Conversions
- Topic: Calculator Question
- Replies: 13
- Views: 703
Re: Calculator Question
It sounds like a plain old scientific or four-function should serve you well. Personally, I use the Casio - fx115ES Plus Scientific calculator. I remember that AP Chem in high school didn't really need a graphing calculator, so I suppose that's why Chem 14A doesn't necessarily require one, either.
- Sun Sep 29, 2019 7:40 pm
- Forum: SI Units, Unit Conversions
- Topic: Memorizing Metric Conversions
- Replies: 8
- Views: 924
Re: Memorizing Metric Conversions
Hey there!
You did receive a reply already, but here's a similar mnemonic that I used in high school that might be of help to you:
Kings Have Died Under Dreadful Circumstances: Meteors
They don't always make sense, but if you create your own mnemonic, that might help you more! :))
You did receive a reply already, but here's a similar mnemonic that I used in high school that might be of help to you:
Kings Have Died Under Dreadful Circumstances: Meteors
They don't always make sense, but if you create your own mnemonic, that might help you more! :))
- Sun Sep 29, 2019 7:31 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Advice from a Medical Student - Part II [ENDORSED]
- Replies: 298
- Views: 244884
Re: Advice from a Medical Student - Part II [ENDORSED]
Your journey sounds like it has been amazing! As someone that also wants to go into the medical field, this is very inspiring. And you certainly made me more excited for Dr. Lavelle's class. Do you currently have other interests outside the medical field, and do you still have time to engage in them...