Search found 103 matches

by Aarja Pavade 1H
Wed Mar 11, 2020 1:50 pm
Forum: Experimental Details
Topic: Collision Theory
Replies: 8
Views: 346

Re: Collision Theory

Based off of what we went over in lecture, know that at higher temperatures, there are more collisions and that reactants must collide with enough energy to break bounds, thus overcoming the activation energy barrier. Furthermore, reactants must have the correct orientation when they collide (freque...
by Aarja Pavade 1H
Wed Mar 11, 2020 1:39 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Rate Laws
Replies: 3
Views: 26

Re: Rate Laws

Rate laws for a reaction are determined experimentally and cannot be inferred from sole inspection of a chemical equation. However, for elementary reactions, you can use the number of reactant molecules to determine the rate law. For instance, a unimolecular reaction would have a first-order rate la...
by Aarja Pavade 1H
Wed Mar 11, 2020 1:32 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Difference between catalyst and intermediate
Replies: 9
Views: 29

Re: Difference between catalyst and intermediate

A catalyst participates in a reaction but is never consumed. It will not be produced in one reaction and then used up. However, intermediates can be consumed. Both will cancel out in the overall reaction.
by Aarja Pavade 1H
Wed Mar 11, 2020 1:24 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7D.7
Replies: 3
Views: 24

Re: 7D.7

For a, you would use the equation K=kr/k'r. For b, you would compare the activation energies of the forwards and reverse reactions.If the reaction is endothermic, the activation energy will be higher for the forward reaction and lower for the reverse reaction and if the reaction is exothermic, the a...
by Aarja Pavade 1H
Wed Mar 11, 2020 1:09 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Reaction orders
Replies: 3
Views: 16

Re: Reaction orders

According to the book, the rate law (which can tell us the order of reaction) cannot in general be inferred from the chemical equation for the reaction. Thus, looking at stoichiometric coefficients are not a reliable way to determine the order of reactions.
by Aarja Pavade 1H
Sun Mar 08, 2020 2:33 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: activation energy/ energy barrier
Replies: 6
Views: 49

Re: activation energy/ energy barrier

According to the book, when you have a high activation energy, there is also high sensitivity of the rate constant to changes in temperature.
by Aarja Pavade 1H
Sun Mar 08, 2020 2:27 pm
Forum: First Order Reactions
Topic: how to know actual order
Replies: 4
Views: 70

Re: how to know actual order

If given a plot, you can use that to determine the order of the plot. For instance, a straight-line plot of ln[A] vs time would be a first-order reaction, 1/[A] vs time means its second-order, and [A] vs time means its zero-order.
by Aarja Pavade 1H
Sun Mar 08, 2020 2:15 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Elementary reactions
Replies: 5
Views: 44

Re: Elementary reactions

Each elementary step reaction describes a distinct event in the progress of a reaction such as a collision of particles. Thus, the sum of elementary steps will give us the overall reaction.
by Aarja Pavade 1H
Sun Mar 08, 2020 2:05 pm
Forum: General Rate Laws
Topic: integrated rate laws
Replies: 7
Views: 52

Re: integrated rate laws

In a rate law (differential rate law) rate is a function of concentration while in an integrated rate law the rate is a function of time.
by Aarja Pavade 1H
Sun Mar 08, 2020 1:59 pm
Forum: General Rate Laws
Topic: average rate vs instantaneous
Replies: 2
Views: 37

Re: average rate vs instantaneous

The instantaneous rate represents the rate of change of [R] or [P] at a specific time (using the slope of the tangent) whereas the average rate looks at the change in [R] or [P] over the change in time (delta[concentration]/delta(time)).
by Aarja Pavade 1H
Sun Mar 08, 2020 1:51 pm
Forum: General Rate Laws
Topic: Graphs of rate laws
Replies: 8
Views: 45

Re: Graphs of rate laws

All of the graphs will be linear, but the slopes will vary. For instance, the graph of a first-order and zero-order reaction will have a decreasing slope of -k while a second-order reaction will have an increasing slope of k.
by Aarja Pavade 1H
Sun Mar 01, 2020 1:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7 a Cell Diagram
Replies: 1
Views: 35

Re: 6L.7 a Cell Diagram

The order for a cell diagram is based off of the phases of the elements. It is s|g|aq||aq|g|s with the anode on the left of the salt bridge and cathode on the right. Thus, AgBr (s) would come before Br-(aq) in the cell diagram.
by Aarja Pavade 1H
Sun Mar 01, 2020 1:35 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.7
Replies: 1
Views: 25

Re: 6N.7

Based off of the problem, you already know the oxidation and reduction reactions. One way to figure out which elements are products/reactants is to combine the half-reactions to write out the whole reaction and determine it from there.
by Aarja Pavade 1H
Sun Mar 01, 2020 1:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Graphite VS. Platinum
Replies: 2
Views: 32

Re: Graphite VS. Platinum

An chemically inert metallic conductor could be any unreactive metal or graphite. Platinum is generally used more often, but graphite or other unreactive metals could be used instead.
by Aarja Pavade 1H
Sat Feb 29, 2020 4:57 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.5 a
Replies: 2
Views: 34

Re: 6N.5 a

To get rid of the power, remember that ln([H+]^2) is the same as 2(ln[H+]). Continue with your algebraic manipulation and then divide by 2 to get ln[H+]. Hopefully this helps!
by Aarja Pavade 1H
Sat Feb 29, 2020 4:53 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cells and Nernst Equation
Replies: 4
Views: 29

Re: Concentration Cells and Nernst Equation

The Nernst Equation is essentially the equation for the concentration dependence of the cell potential. This is why it is generally applied to a concentration cell or other cells where the concentrations are not at equilibrium.
by Aarja Pavade 1H
Sat Feb 22, 2020 9:28 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining if a cell reaction is spontaneuous
Replies: 5
Views: 36

Re: Determining if a cell reaction is spontaneuous

From thermodynamics, we learned that if deltaG is negative the reaction is spontaneous. When applying this to electrochemistry and looking at the equation deltaG=-nFE, we see that a negative deltaG is acquired when E is positive. This makes sense as it was discussed in lecture that a positive voltag...
by Aarja Pavade 1H
Sat Feb 22, 2020 4:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Example
Replies: 3
Views: 27

Re: Cell Diagram Example

The iron is in an aqueous phase, meaning that it is not a conducting solid. Thus, in the way that Cu (s) acts as an electrode, we use an inert conductor(Pt (s)) as an electrode to transfer electrons on the side with the iron.
by Aarja Pavade 1H
Sat Feb 22, 2020 4:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: max potential in Galvanic Cell
Replies: 4
Views: 21

Re: max potential in Galvanic Cell

The potential difference is concerned with electron flow between the electrodes, so I believe that the current flow is in reference to the electron flow. Thus, when there is "very little current flow" I think it means that there is little electron flow and the cell is at its maximum potent...
by Aarja Pavade 1H
Sat Feb 22, 2020 4:43 pm
Forum: Balancing Redox Reactions
Topic: Basic/Acidic solutions
Replies: 2
Views: 23

Re: Basic/Acidic solutions

In an acidic solution, you would balance H with H+ which makes sense because in an acidic solution more H+ are present. In an alkaline (basic) solution, however, there will be more OH- and less H+ so to balance the reaction, you would replace the H+ added with OH- as discussed above.
by Aarja Pavade 1H
Sat Feb 22, 2020 4:38 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: E° as state function?
Replies: 3
Views: 65

Re: E° as state function?

Consider E° is an intensive property, meaning that the voltage difference will remain the same and not depend on how many times the reaction occurs. It gives the voltage difference between 2 standard electrodes (cathode-anode) which is always the same.
by Aarja Pavade 1H
Thu Feb 13, 2020 9:09 pm
Forum: Phase Changes & Related Calculations
Topic: Relation to entropy?
Replies: 4
Views: 57

Re: Relation to entropy?

In order of decreasing entropy: S(gas)>S(liquid)>S(solid). Thus, for processes such a melting and vaporization we see an increase in entropy as there is now more disorder. However, when the system becomes more ordered (condensation/freezing), we see a decrease in entropy.
by Aarja Pavade 1H
Thu Feb 13, 2020 9:06 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: How do I do? [ENDORSED]
Replies: 2
Views: 45

Re: How do I do? [ENDORSED]

You can also use standard Gibbs free energy of formation (Gf) in the same way you use standard enthalpies of formation (Hf). You would just take the sum of Gf for the products and subtract the sum of Gf for the reactants to obtain Grxn.
by Aarja Pavade 1H
Thu Feb 13, 2020 8:58 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: Laws of thermodynamics
Replies: 3
Views: 60

Re: Laws of thermodynamics

The 2nd law says that systems spontaneously go towards states of maximum entropy, which is shown by the equation, delta s=q/T. This is also demonstrated by Gibbs free energy equation because systems that are exothermic and have high entropy are spontaneous. For the third law, it's saying that as th...
by Aarja Pavade 1H
Thu Feb 13, 2020 8:54 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Enthalpies
Replies: 3
Views: 55

Re: Enthalpies

For example, the book provides the reaction C(gr)-->C(gr) in which nothing changes, so the standard enthalpy of formation would be 0. The conversion of C(gr) into C(diamond), however, is endothermic and has a nonzero standard enthalpy of formation since the element is in a form different than its no...
by Aarja Pavade 1H
Thu Feb 13, 2020 8:48 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Units in Entropy Equation for Volume
Replies: 5
Views: 66

Re: Units in Entropy Equation for Volume

PV/T would give you units of L*atm/K. You can then use the conversion of 101.325 J/L*atm to cancel out units and end up with the units for entropy (J/K).
by Aarja Pavade 1H
Thu Feb 13, 2020 8:45 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Mean bond enthalpies
Replies: 3
Views: 39

Re: Mean bond enthalpies

Instead of thinking of them as being products and reactants, it is much easier if you think of it as bonds broken (reactants) - bonds formed (products). Since all bond enthalpies are positive because heat must be supplied to break a bond, you will need to taken into consideration that bond breaking ...
by Aarja Pavade 1H
Sat Feb 08, 2020 10:23 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Negative Heat Capacity
Replies: 4
Views: 33

Re: Negative Heat Capacity

Heat capacity is defined as the heat required to raise the temperature of an object by 1 degree C. Since we are trying to raise the temperature, heat must be added and thus should be a positive input.
by Aarja Pavade 1H
Sat Feb 08, 2020 10:20 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Spontaneous reactions
Replies: 3
Views: 25

Re: Spontaneous reactions

If delta S is larger than delta H, it would make delta G negative (spontaneous). However, we would need to know the exact values for this. Another situation in which the reaction is spontaneous is if delta H is negative and delta S is positive. Subtracting a positive from a negative gives us a negat...
by Aarja Pavade 1H
Sat Feb 08, 2020 10:16 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy as an extensive property
Replies: 2
Views: 17

Re: Entropy as an extensive property

An extensive property depends on the amount of material while an intensive property is inherent and doesn't change. Entropy depends on the number of particles, so we would consider it to be an extensive property
by Aarja Pavade 1H
Sat Feb 08, 2020 10:13 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: Perfect Crystal
Replies: 3
Views: 14

Re: Perfect Crystal

This relates to the third law of thermodynamics which states that for perfectly ordered material (no thermal or positional disorder) the entropy is 0.
by Aarja Pavade 1H
Sat Feb 08, 2020 10:07 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Units
Replies: 4
Views: 31

Re: Units

Entropy is generally calculated in units of J/K. When you take the ln of 2 volumes/temperatures, the units of both will cancel with each other (ln(373 K/323 K)=ln(373/323)). We will be left with units of n (moles) and R (JK^-1mol^-1) which will cancel out to give us J/K.
by Aarja Pavade 1H
Sat Feb 01, 2020 5:53 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed Systems
Replies: 8
Views: 42

Re: Closed Systems

If you think of an isolated system as being insulated, it would make sense that it would retain energy and not lose it to the surroundings (ex: thermos). Closed systems, on the other hand, are sealed but not insulated. This means that that energy exchange can happen between the system and its surrou...
by Aarja Pavade 1H
Sat Feb 01, 2020 5:48 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: isolated system
Replies: 13
Views: 55

Re: isolated system

An example of an isolated system is combustion go glucose in a bomb calorimeter. The calorimeter is sealed and insulated so that nothing exchanges with the surroundings. A real life example would be coffee/tea kept in a thermos. The thermos is sealed and insulated so it retains heat, keeping the cof...
by Aarja Pavade 1H
Sat Feb 01, 2020 3:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4C.3
Replies: 2
Views: 29

Re: 4C.3

In Focus 4C.3 of the textbook, it states that for a monatomic gas, such as Kr, Cp= 5/2R.
by Aarja Pavade 1H
Thu Jan 30, 2020 10:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: hess's law
Replies: 13
Views: 64

Re: hess's law

Yes, to cancel out they must be on opposite sides of a reaction. A product forms while a reactant is used up. If H2 is formed in one reaction (product) and is then used as a reactant (with the equivalent amount of moles) in another reaction, it will cancel out. Using this same rationale, if they wer...
by Aarja Pavade 1H
Thu Jan 30, 2020 10:21 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: qp=deltaH
Replies: 2
Views: 35

Re: qp=deltaH

We are looking at the heat required to heat a gas at constant pressure. In the book, it states that at constant pressure, and with no non-expansion work: deltaH=q. In other words, the change in enthalpy of a system (deltaH) is equal to the heat supplied to the system at constant pressure (qp).
by Aarja Pavade 1H
Sun Jan 26, 2020 1:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method One (Hess’s Law)
Replies: 4
Views: 33

Re: Method One (Hess’s Law)

Hess's Law states that enthalpy changes are additive. Thus, the enthalpy change at each step of a multi-step reaction can be added to give the total enthalpy change. ex: delta Hrxn1 + delta Hrxn2= delta Hnet (adding reactions to obtain net reaction).
by Aarja Pavade 1H
Sun Jan 26, 2020 1:27 pm
Forum: Phase Changes & Related Calculations
Topic: steam vs liquid burn
Replies: 2
Views: 19

Re: steam vs liquid burn

When we look at the heating curve for water, we see that there is more heat being supplied to turn the liquid into vapor. The enthalpy of vaporization is considerably large for water, which means that the enthalpy on condensation (when steam touches a cold surface/skin) will be a large, exothermic r...
by Aarja Pavade 1H
Fri Jan 24, 2020 10:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: O2 Delta Hf
Replies: 2
Views: 13

Re: O2 Delta Hf

By definition, the standard enthalpy of formation of an element in its most stable form is zero. Thus, this does not just apply to diatomic molecules, but to all elements in their most stable forms.
by Aarja Pavade 1H
Fri Jan 24, 2020 9:55 pm
Forum: Phase Changes & Related Calculations
Topic: Steam v. liquid
Replies: 7
Views: 55

Re: Steam v. liquid

Yes, since the enthalpy of vaporization (steam) is very large for water, the enthalpy of condensation is very large and exothermic, releasing more energy and causing more severe burns.
by Aarja Pavade 1H
Fri Jan 24, 2020 9:48 pm
Forum: Phase Changes & Related Calculations
Topic: Endothermic values
Replies: 5
Views: 32

Re: Endothermic values

The plus sign reinforces the fact the delta H is positive and that heat is needed ("added") for the reaction. It would not necessarily be wrong if you left it out, however, since the value would still be positive, but it is good to keep it to be explicit and clear.
by Aarja Pavade 1H
Sat Jan 18, 2020 11:25 pm
Forum: Ideal Gases
Topic: Ideal Gas meaning
Replies: 7
Views: 63

Re: Ideal Gas meaning

At low temperatures, most gases are going to act ideally. In this course, we'll probably only deal with ideal gases because this allows for us to apply PV=nRT and infer molecular kinetic energy based on temperature. How do we know when to apply the ideal gas equation in a problem? The ideal gas equ...
by Aarja Pavade 1H
Sat Jan 18, 2020 11:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatliers Principle In relation to pressure
Replies: 6
Views: 41

Re: Le Chatliers Principle In relation to pressure

More molecules would essentially mean less volume. The more particles you add into an empty flask, the less empty space there is. Since there is less volume, the pressure in the flask will increase. This is demonstrated through the inverse relationship between pressure and volume and the equation P=...
by Aarja Pavade 1H
Sat Jan 18, 2020 11:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Questions and Sig Figs
Replies: 6
Views: 58

Re: Equilibrium Questions and Sig Figs

I agree with the last user's post in that it is best to round to the number of given sig figs at the very end. When dealing with pH however, the sig figs are typically calculated differently (calculated in the way of a logarithm) which I believe is 3 sig figs usually. For pH, the sig figs in the gi...
by Aarja Pavade 1H
Sat Jan 18, 2020 5:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K and Kc
Replies: 3
Views: 34

Re: K and Kc

Since we have not done examples/homework problems relating to converting K to Kc as in example 5H.1, I do not believe we are expected to know this for Test 1. However, you should know how to convert from concentration to pressure in situations where you are given bars and are expected to calculate K...
by Aarja Pavade 1H
Sat Jan 18, 2020 2:48 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.1 a)
Replies: 5
Views: 37

Re: 5J.1 a)

Both H2 and CO2 will need to react together in order to make more reactants (the reverse reaction). Thus, the partial pressure of H2 will also have to decrease.
by Aarja Pavade 1H
Sun Jan 12, 2020 1:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Temperature and K
Replies: 6
Views: 54

Re: Temperature and K

If the reaction is endothermic (requires heat) while forming product, heating will favor product formation, increasing K. If the reaction is exothermic (gives off heat) while forming product, then heating it will favor reactant formation, lowering K.
by Aarja Pavade 1H
Sun Jan 12, 2020 1:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: appliction of principle
Replies: 5
Views: 34

Re: appliction of principle

LeChatlier's principle applies to changing concentration and physical parameters such as pressure and temperature. However, only a change in temperature will change the K value. Changing the concentration or pressure will not change K.
by Aarja Pavade 1H
Sun Jan 12, 2020 1:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Factors Affecting K
Replies: 5
Views: 48

Re: Factors Affecting K

Furthermore, the change in concentration does not change K as the chemical reaction at equilibrium represents a fixed product to reactant ratio. The chemical reactions adjust so as to minimize the effect of changes. This is LeChatlier's Principle. K, however, is dependent on the temperature which is...
by Aarja Pavade 1H
Sat Jan 11, 2020 5:19 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Alternative Forms [ENDORSED]
Replies: 2
Views: 34

Re: Alternative Forms [ENDORSED]

It also depends on the states of the molecules. For instance, if given gases and their partial pressure, Kp will be used. For aqueous substances and concentration, Kc will be used. However, you can convert between partial pressure and concentration for a gas by using the ideal gas law and deriving t...
by Aarja Pavade 1H
Sat Jan 11, 2020 5:13 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Adding inert gas [ENDORSED]
Replies: 9
Views: 66

Re: Adding inert gas [ENDORSED]

According to the book, the inert gas increases the total pressure within a reaction vessel. The reacting gases, however, will still occupy the same volume, meaning their concentrations and partial pressures remain the same despite the inert gas. Thus, the introduction of the inert gas has no effect ...
by Aarja Pavade 1H
Sat Dec 07, 2019 2:12 pm
Forum: Conjugate Acids & Bases
Topic: Acid/base reactions
Replies: 3
Views: 82

Re: Acid/base reactions

If you consider H+ as a proton, it should not make sense that Lewis acids will accept H+, as they are electron pair acceptors. If you think about the conjugate base of an acid, it will have a more negative charge than the acid since it has lost a proton/gained an electron pair. Hopefully this helps.
by Aarja Pavade 1H
Sat Dec 07, 2019 2:08 pm
Forum: Lewis Acids & Bases
Topic: strength of bases
Replies: 1
Views: 29

Re: strength of bases

Strong bases include Group 1 and 2 metal oxides and hydroxides. The oxide ion in metal oxide would react with water to form hydroxide ions, making it a strong base. Thus, Li2O is not an exception, but is in fact is strong base.
by Aarja Pavade 1H
Sat Dec 07, 2019 1:41 pm
Forum: Identifying Acidic & Basic Salts
Topic: Knowing strong acids and bases
Replies: 6
Views: 99

Re: Knowing strong acids and bases

Also, memorizing the strong acids and bases will help you recognize which acids and bases will be weak and not completely disassociate, as they will just be any acid/base that is not strong.
by Aarja Pavade 1H
Sat Dec 07, 2019 1:35 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligand Charges
Replies: 3
Views: 44

Re: Ligand Charges

To calculate the charge of the ligand, you would "give back" the lone pair that it donated to the cation and look at the ligand individually (not bonded to the cation).
by Aarja Pavade 1H
Sat Dec 07, 2019 1:31 pm
Forum: Biological Examples
Topic: Charge of Iron in Hemoglobin
Replies: 2
Views: 31

Re: Charge of Iron in Hemoglobin

To figure out the ligand's charge, give back the lone pair that it donated to the cation. This would mean that two of the nitrogens have a formal charge of 0 (1 lone pair, 1 double bond, and 1 single bond) while the other two nitrogens will have a formal charge of -1 (2 lone pairs and 2 single bonds...
by Aarja Pavade 1H
Sun Dec 01, 2019 10:09 pm
Forum: Lewis Acids & Bases
Topic: Arrhenius
Replies: 3
Views: 31

Re: Arrhenius

Just for your reference, Arrhenius acids disassociate into water to form H+ while Arrhenius bases disassociate in water to form OH-.
by Aarja Pavade 1H
Sun Dec 01, 2019 10:02 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Oxoacids
Replies: 2
Views: 26

Re: Oxoacids

Going off the previous post, oxoacids more readily lose H+ if the resulting anion is stabilized by the electron withdrawing atom which delocalize and stabilize the negative charge.
by Aarja Pavade 1H
Sun Dec 01, 2019 9:58 pm
Forum: Lewis Acids & Bases
Topic: Relative acidity
Replies: 4
Views: 30

Re: Relative acidity

Strong acids produce more protons than a weak acid. Strong acids are completely ionized in solution while weak acids are incompletely ionized.
by Aarja Pavade 1H
Sun Dec 01, 2019 9:56 pm
Forum: Lewis Acids & Bases
Topic: Strong versus weak
Replies: 5
Views: 40

Re: Strong versus weak

Strong acids produce more protons in solution than a weak acid, i.e they are completely disassociated. Weak acids are incompletely ionized in solution.Strong bases are completely ionized in water while weak bases are not completely ionized in water.
by Aarja Pavade 1H
Sun Dec 01, 2019 9:49 pm
Forum: Amphoteric Compounds
Topic: amphoteric oxides
Replies: 3
Views: 38

Re: amphoteric oxides

Yes, and between the metal oxides (bases) and nonmetal oxides (acids) there is a diagonal band of amphoteric oxides closely matching the diagonal band of metalloids.
by Aarja Pavade 1H
Sun Nov 24, 2019 3:34 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C. 9
Replies: 1
Views: 20

Re: 9C. 9

The ethylenediamine molecule, NH2CH2CH2NH2, is a polydentate ligand and in formulas is abbreviated to en. EDTA refers to ethylene-diamine-tetra-acetate.
by Aarja Pavade 1H
Sun Nov 24, 2019 3:27 pm
Forum: Biological Examples
Topic: Heme complex
Replies: 8
Views: 90

Re: Heme complex

How would something like this appear on a test? would we define it or say why it's needed or what? I believe that it could have to do with identifying that the Fe bound to the porphyrin ligand is the heme complex or that a heme complex and protein form myoglobin. Knowing the definition would help w...
by Aarja Pavade 1H
Sun Nov 24, 2019 3:20 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: chelating complexes
Replies: 2
Views: 23

Re: chelating complexes

Going off of the previous post, a chelate is a complex that contains a ligand that forms a ring of atoms that includes the central metal atom. The example given to us in class was ethylene-diamine-tetra-acetate.
by Aarja Pavade 1H
Sun Nov 24, 2019 3:12 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Tetrahedral and Square Planar
Replies: 3
Views: 53

Re: Tetrahedral and Square Planar

In lecture, we were given the example of a porphyrin ligand which was stated to be tetradentate square planar.
by Aarja Pavade 1H
Sun Nov 24, 2019 12:53 pm
Forum: Biological Examples
Topic: Biological Examples
Replies: 3
Views: 29

Re: Biological Examples

Additionally, I think it is good to review hemoglobin in addition to myoglobin. For instance, know that myoglobin relates to the transport of oxygen in muscle cells while hemoglobin relates to the transport of oxygen in the blood and has 4 myoglobin-like molecules.
by Aarja Pavade 1H
Sun Nov 24, 2019 12:47 pm
Forum: Naming
Topic: Polydentate Ligands
Replies: 2
Views: 24

Re: Polydentate Ligands

Polydentate essentially means "many-toothed". These ligands can occupy more than one binding site simultaneously. You would use the prefixes bis-, tris-, tetrakis-, pentakis- for polydentate ligands.
by Aarja Pavade 1H
Sun Nov 17, 2019 6:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs
Replies: 5
Views: 42

Re: Lone Pairs

The shapes with lone pairs are bent, trigonal pyramidal, seesaw, T-shape, linear, square pyramid, and square planar. Some of these names overlap for the basic geometry shapes (ex: both trigonal planar and tetrahedral have bent shapes, but for trigonal planar 1 lone pair creates a bent shape vc tetra...
by Aarja Pavade 1H
Sun Nov 17, 2019 6:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion
Replies: 2
Views: 29

Re: Repulsion

Repulsion influences the molecular shape as it can force bonding electrons closer together, reducing their bond angle. For instance, a molecule with a tetrahedral shape has bond angles of 109.5 but once lone pairs are introduced, there is greater repulsion and the bond angles decrease to <109.5 with...
by Aarja Pavade 1H
Sat Nov 16, 2019 11:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR notation
Replies: 8
Views: 71

Re: VSEPR notation

Single, double, and triple bonds are considered single regions of electron density in the VSEPR model, so even though there is a double bond between N and O, the VSEPR notation would still be AX3.
by Aarja Pavade 1H
Sat Nov 16, 2019 9:45 pm
Forum: Bond Lengths & Energies
Topic: Lone pairs
Replies: 7
Views: 106

Re: Lone pairs

The lone pairs can either be axial or equatorial. The axial lone pairs lie on the axis of the molecule and the equatorial lone pairs lie on the equator of the molecule, the plane perpendicular to the axis.
by Aarja Pavade 1H
Sat Nov 16, 2019 9:40 pm
Forum: Dipole Moments
Topic: Dipole Moment
Replies: 3
Views: 44

Re: Dipole Moment

Furthermore, the dipole moments help us figure out if a molecule is polar or non polar. This classification will allow us to figure out what type of bonds/intermolecular forces are present within a molecule. For example, if the dipole moments do not cancel, the molecule is polar. A non polar molecul...
by Aarja Pavade 1H
Sat Nov 09, 2019 10:30 pm
Forum: Electronegativity
Topic: Ionization Energy
Replies: 3
Views: 37

Re: Ionization Energy

I believe you're asking why nitrogen has a higher ionization energy than oxygen. This is because nitrogen is more stable. Looking at its electron configuration, nitrogen has 3 electrons in is p-orbital meaning that each orbital contains one electron. Oxygen, on the other hand has 4 electrons its p-o...
by Aarja Pavade 1H
Sat Nov 09, 2019 10:18 pm
Forum: Dipole Moments
Topic: Instantaneous dipoles
Replies: 2
Views: 24

Re: Instantaneous dipoles

According to the book, an instantaneous dipole moment is a momentary dipolar separation of charge. In an instant, a region of a molecule can have a partial negative charge while the other has a partial positive charge.
by Aarja Pavade 1H
Sat Nov 09, 2019 10:07 pm
Forum: Bond Lengths & Energies
Topic: Positive Dissociation Energy & Negative Interaction Potential Energy
Replies: 1
Views: 30

Re: Positive Dissociation Energy & Negative Interaction Potential Energy

In class, it was explained that since disassociation energy is the energy required to break a bond, it is always positive. The interaction potential energy is negative, however, because it is always an attractive force(the charges have opposite signs).
by Aarja Pavade 1H
Sat Nov 09, 2019 10:02 pm
Forum: Bond Lengths & Energies
Topic: Dissociation Energy
Replies: 5
Views: 40

Re: Dissociation Energy

Furthermore, since the disassociation energy is the energy required to break a bond, it measures the strength of the bond and is also always positive.
by Aarja Pavade 1H
Sat Nov 09, 2019 9:52 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarisability Trend
Replies: 3
Views: 25

Re: Polarisability Trend

Furthermore, small, highly charged cations such as Al3+ also have high polarizing power.
by Aarja Pavade 1H
Sat Nov 02, 2019 6:51 pm
Forum: Electronegativity
Topic: Definition
Replies: 2
Views: 30

Re: Definition

While the above definition is correct, electronegativity has the same trend as ionization energy, not atomic radius. It increases across a period and decreases down a group.
by Aarja Pavade 1H
Sat Nov 02, 2019 6:47 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Minimize formal charge of whole molecule?
Replies: 7
Views: 55

Re: Minimize formal charge of whole molecule?

Keep in mind that if the molecule has a specific charge you would want to keep that charge, not make it 0. For instance, in the sulfate ion (SO4 2-), two oxygens will have to have a -1 charge so that the total charge remains -2. We assign the negative charge to oxygen instead of sulfur, though, beca...
by Aarja Pavade 1H
Sat Nov 02, 2019 6:40 pm
Forum: Electronegativity
Topic: which bond
Replies: 4
Views: 64

Re: which bond

If the electronegativity difference is greater than 2, it is an ionic bond. If it is less than 1.5 it is a covalent bond.
by Aarja Pavade 1H
Sat Nov 02, 2019 6:36 pm
Forum: Lewis Structures
Topic: Expanded Valence Shells
Replies: 3
Views: 33

Re: Expanded Valence Shells

The octet guideline refers to 8 electrons. This gives us the configuration of s2p6. For atoms in Period 3 or higher, their n (principal quantum number) is 3. This gives us an l of 0,1,2, meaning that they have an s,p,and d orbital. The d-orbitals allow Period 3 and higher elements to accommodate the...
by Aarja Pavade 1H
Sat Nov 02, 2019 6:31 pm
Forum: Sigma & Pi Bonds
Topic: Double bond
Replies: 15
Views: 157

Re: Double bond

Two things to pay attention to are formal charge and octets. Most elements want to have a full shell of valence electrons, so try to make sure that they all have 8 electrons around them. Next is to pay attention to the formal charge. If by forming a double bond, the formal charge is closer to 0, th...
by Aarja Pavade 1H
Sat Oct 26, 2019 11:48 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Formal Charge
Replies: 3
Views: 39

Re: Formal Charge

Furthermore, keep in mind that the total charge still has to remain the same. For instance, in class we looked at the example of the sulfate ion (SO4^2-). Here, only two of the oxygen atoms had a formal charge of 0 while the other two each had a charge of -1. This is to ensure that the 2- charge of ...
by Aarja Pavade 1H
Sat Oct 26, 2019 11:39 am
Forum: Trends in The Periodic Table
Topic: Exceptions to Octet Rule
Replies: 2
Views: 26

Re: Exceptions to Octet Rule

Atoms in period 3 or higher (such as P,S and Cl) have d-orbitals in valence shells that can accommodate additional electrons. The octet rule goes up to the p-orbital as 8 valence electrons means an electron configuration of s^2p^6. Thus, atoms with d- or even f-orbitals can accommodate more than 8 v...
by Aarja Pavade 1H
Sat Oct 26, 2019 11:33 am
Forum: Trends in The Periodic Table
Topic: ionic radius
Replies: 3
Views: 29

Re: ionic radius

An ionic radius is simply half the distance between the centers of two ions that are joined by an ionic bond. I think that the value is usually given to us, but we might have to do calculations converting it from pm (what it is measured in) to meters or Angstroms. To do this you would just need to k...
by Aarja Pavade 1H
Sat Oct 26, 2019 11:23 am
Forum: Quantum Numbers and The H-Atom
Topic: ionization energy and electron affinty
Replies: 3
Views: 41

Re: ionization energy and electron affinty

Electron affinity is the energy released when electrons are added to a gas-phase atom while ionization energy is the energy ended to remove electrons from an atom (gas-phase). There is generally a high electron affinity for Group 17 atoms.
by Aarja Pavade 1H
Sat Oct 26, 2019 11:20 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Drawing Lewis Structures
Replies: 5
Views: 78

Re: Drawing Lewis Structures

Going off of the previous comment, atoms in period 3 or higher (such as P,S, and Cl) have d-orbitals in valence shells that accommodate more than 8 valence electrons, deviating from the octet guideline.
by Aarja Pavade 1H
Sat Oct 19, 2019 8:07 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configuration for Ag
Replies: 2
Views: 39

Re: Electron configuration for Ag

When we looked at the Scandium example, we saw that the right way to write the electron configuration was [Ar]3d14s2 because for multi-electron atoms after atomic number 20 the 4s state is higher in energy than 3d. Period 5 shows this same trend where after 2 electrons have occupied the 5s state the...
by Aarja Pavade 1H
Sat Oct 19, 2019 5:56 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 3d and 4s
Replies: 4
Views: 49

Re: 3d and 4s

After the 4s state/orbital is occupied and electrons enter the 3d state, the 3d state would be lower in energy than the 4s state. This occurs for multi electron atoms after the atomic number 20 (Calcium). For Scandium (z=21), you would put 3d1 before 4s2 because the 4s state is higher in energy than...
by Aarja Pavade 1H
Sat Oct 19, 2019 4:45 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: electrostatic (coulomb) potential energy [ENDORSED]
Replies: 3
Views: 50

Re: electrostatic (coulomb) potential energy [ENDORSED]

Furthermore, he wanted us to understand the relationship between the charges and the electrostatic potential energy as well as the relationship between the distance of the charges and the electrostatic potential energy. From the equation E=(q1)(q2)/r, we see that the energy is directly proportional ...
by Aarja Pavade 1H
Sat Oct 19, 2019 4:34 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Hund's rule and Pauli Exclusion Principle
Replies: 14
Views: 134

Re: Hund's rule and Pauli Exclusion Principle

We apply both Pauli Exclusion Principle and Hund's Rule to obtain the ground state electron configuration.
by Aarja Pavade 1H
Sat Oct 19, 2019 4:23 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Lobes
Replies: 2
Views: 35

Re: Lobes

Lobes also refer to areas of electron density located in xy-yz-zx planes.
by Aarja Pavade 1H
Sun Oct 13, 2019 4:10 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: atomic spectra
Replies: 5
Views: 81

Re: atomic spectra

In transitions of electrons between energy levels in an atom, as a high energy electron drops to a lower energy level, the difference in energy is given off as a photon. The atomic spectra refers to this spectrum of light emitted and shows the different groups of spectral lines. It is also unique fo...
by Aarja Pavade 1H
Sun Oct 13, 2019 2:56 pm
Forum: Photoelectric Effect
Topic: ejecting electons
Replies: 6
Views: 65

Re: ejecting electons

Only one photon interacts with one electron and each photon must have enough energy to eject one electron. If the energy per photon is greater than or equal to the energy needed to remove an electron, then increasing the light intensity (increasing the number of photons) would result in more ejected...
by Aarja Pavade 1H
Sun Oct 13, 2019 2:48 pm
Forum: Properties of Light
Topic: black body radiation
Replies: 2
Views: 46

Re: black body radiation

Electrons in atoms and molecules absorb or emit quanta of energy, which gives atom (and molecular) spectra. Atoms and molecules only absorb or emit unique frequencies that are allowed by their unique electronic structure. This is unlike "black bodies" that absorb or emit a broad range of w...
by Aarja Pavade 1H
Sat Oct 12, 2019 10:51 pm
Forum: Photoelectric Effect
Topic: Classic Wave in Photoelectric effect
Replies: 5
Views: 61

Re: Classic Wave in Photoelectric effect

Increasing the light intensity only increases the number of photons. To remove electrons, we need the energy of the photon to be greater than or equal to the energy needed to remove an electron. If you have this energy, then increasing the light intensity results in more ejected electrons. Light doe...
by Aarja Pavade 1H
Sat Oct 12, 2019 10:37 pm
Forum: Properties of Light
Topic: Photoelectric Effect
Replies: 3
Views: 71

Re: Photoelectric Effect

Furthermore, the photoelectric experiment that light sources with long wavelengths (low frequency) cannot eject electrons. This is because energy is inversely proportional to wavelength. However, light sources with short wavelengths (high frequency) will have higher energy so they will be able to ej...
by Aarja Pavade 1H
Sun Oct 06, 2019 2:08 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Mole help [ENDORSED]
Replies: 8
Views: 118

Re: Mole help [ENDORSED]

Also, keep in mind that in chemistry, atoms are not created or destroyed. As mentioned before, since moles refer to the number of atoms, moles of solute will always remain the somewhen diluting a solution.
by Aarja Pavade 1H
Sun Oct 06, 2019 1:57 pm
Forum: Balancing Chemical Reactions
Topic: Differentiating between elements are molecules or single
Replies: 4
Views: 88

Re: Differentiating between elements are molecules or single

Also, since oxygen gas does occur as a diatomic molecule, make sure that when you balance equations you take into account that it is double. For instant you might have O2 on on side of the equation and O on the other. If you have 4O2, the O must be doubled (8O) since it is a monatomic molecule.

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