Search found 52 matches

by skalvakota2H
Wed Mar 14, 2018 4:42 pm
Forum: First Order Reactions
Topic: Determining Reaction Order
Replies: 5
Views: 294

Re: Determining Reaction Order

The reaction order is determined experimentally. Thus, the pattern is as follows: If the reactant concentration is doubled and the rate is unchanged, then the reactant is zero order. If the reactant concentration is doubled and the rate is doubled, then the reactant is first order. If the reactant c...
by skalvakota2H
Wed Mar 14, 2018 4:34 pm
Forum: *Enzyme Kinetics
Topic: Enzymes in rate law
Replies: 4
Views: 281

Re: Enzymes in rate law

Catalysts can be included in the rate law. This occurs when the catalyst is involved in the rate-determining step, since the reactants of the rate-determining step is what decides the overall rate law. However, if the catalyst is involved in a different step, then it will not appear in the rate law.
by skalvakota2H
Wed Mar 14, 2018 4:28 pm
Forum: *Amines
Topic: amine
Replies: 2
Views: 337

Re: amine

The amine functional group is a nitrogen atom with three bonds, and one of which is the carbon atom. This means that nitrogen can form two other bonds and is not restricted to hydrogen for those bonds.
by skalvakota2H
Sat Mar 10, 2018 9:56 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: SN2 Organic Reaction
Replies: 3
Views: 130

Re: SN2 Organic Reaction

A nucleophile is a species that will donate an electron pair to form a chemical bond. These nucleophiles can take part in substitution reactions, in which the nucleophile is attracted to a full or partial positive charge, and it serves as a replacement for a leaving group.
by skalvakota2H
Fri Mar 09, 2018 12:21 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Negative Order
Replies: 7
Views: 1020

Re: Negative Order

A negative order means that the concentration of a species inversely affects the rate of a reaction.
by skalvakota2H
Fri Mar 09, 2018 12:14 pm
Forum: Zero Order Reactions
Topic: Half Lives? [ENDORSED]
Replies: 7
Views: 456

Re: Half Lives? [ENDORSED]

In general, at any stage of the reaction, we can find how much of a reactant is remaining after n half-lives by (1/2)^n [A]0. Thus, if 1/2 is a factor of the remaining amount, then it is allowed to use the half life method.
by skalvakota2H
Sun Mar 04, 2018 1:48 am
Forum: General Rate Laws
Topic: 15.13 part a?
Replies: 3
Views: 148

Re: 15.13 part a?

Note that the equation for the formation of HI is given by: H2 + I2 → 2 HI Since the question gives that each reactant is to the first order, this means that the total order, given by the sum of individual orders for each reactant, is 1+1, or 2. A reaction need not be dependent on only one reactant ...
by skalvakota2H
Sun Mar 04, 2018 1:38 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Importance of n and k
Replies: 2
Views: 129

Re: Importance of n and k

The order of a reactant, n, explains more about the reaction mechanism because it directly describes how the concentration of a reactant affects the rate of the reaction. From this, the rate law can be used to calculate the reaction rate using known concentrations of reactants.
by skalvakota2H
Sun Mar 04, 2018 1:26 am
Forum: First Order Reactions
Topic: Pseudo-1st-Order
Replies: 6
Views: 257

Re: Pseudo-1st-Order

Pseudo rate laws are useful in finding the overall rate law when a reaction has multiple reactants with changing concentrations. What this allows is to assume that the concentrations of the other reactants do not change, so the reaction appears as a first order.
by skalvakota2H
Tue Feb 20, 2018 11:16 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Electromotive Force
Replies: 1
Views: 106

Re: Electromotive Force

Electromotive force is the cell potential of a system. A higher potential implies that the chemical reaction provides an electric current that is sufficient enough to electrons to transfer. As a result, this means that there is no need for outside input, and the reaction is spontaneous. From this, w...
by skalvakota2H
Tue Feb 20, 2018 9:24 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Example 14.7
Replies: 1
Views: 97

Re: Example 14.7

A way to determine which species is reduced and/or oxidized is by comparing the values of standard potentials for the species. Whichever one has the more positive potential, this species is the one with greater electron-pulling power as a reduction half reaction, meaning this species is more likely ...
by skalvakota2H
Tue Feb 20, 2018 9:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: E standard
Replies: 1
Views: 82

Re: E standard

Typically, when we flip the reduction half reaction so that the electrons are on the left hand side, we are required to change the sign of E°. However, when we are using the E°cell=E°cathode-E°anode, the subtraction operation already accounts for the sign switch, hence we can use the standard reduct...
by skalvakota2H
Tue Feb 13, 2018 9:28 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: W
Replies: 3
Views: 297

Re: W

W is the number of microstates that a particular atom or molecule can take. A good way to find the value for W is to consider the form:
(number of states)^(number of particles).
This means that the base refers to the orientation of the particular atom/molecule.
by skalvakota2H
Tue Feb 13, 2018 9:20 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.65
Replies: 1
Views: 120

Re: 9.65

The thermodynamic stability of a molecule means that the formation is favored, so the reaction is spontaneous. The way by which we can determine spontaneity from Gibbs Free Energy is by using the equation deltaG = deltaH - TdeltaS. This allows us to compare how altering the values of the variables w...
by skalvakota2H
Tue Feb 13, 2018 9:12 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Heat and Enthalpy
Replies: 1
Views: 138

Re: Heat and Enthalpy

Heat is the transfer of energy due to a difference in temperature. On the other hand, enthalpy is the change in amount of heat in a system at constant pressure. This means that heat is a path dependent function, while enthalpy is a state function.
by skalvakota2H
Fri Feb 09, 2018 12:33 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cell
Replies: 3
Views: 118

Re: Galvanic Cell

A galvanic cell is simply the electrochemical cell that uses the transfer of energy in redox reactions, which supplies an electric current. It comprises of two half cells connected by a salt bridge, and the transfer of electrons is spontaneous. As a result, there will always be a positive voltage
by skalvakota2H
Thu Feb 08, 2018 9:34 pm
Forum: Balancing Redox Reactions
Topic: 14.5
Replies: 4
Views: 185

Re: 14.5

The half reaction would need to be balanced first, so the equation would look like H2O (l) + O3 (g) + 2e- --> O2 (g) + 2OH- (aq). As mentioned, both O3 and O2 have no charge, but since the products contains two hydroxide ions, the overall charge needs to be balanced by adding two electrons to the le...
by skalvakota2H
Thu Feb 08, 2018 9:29 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.81
Replies: 2
Views: 116

Re: 11.81

I believe a description of the changes in the reaction due to increase in temperature is acceptable. As mentioned, by observing that the equilibrium constant decreases, this implies increased reactant formation. As a result, this deems that there will be less ammonia formed upon heating.
by skalvakota2H
Thu Feb 01, 2018 9:40 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.7
Replies: 7
Views: 230

Re: 9.7

We can substitute the expressions for the heat capacities at both constant volume and pressure if we are aware of the molecular complexity. This means classifying the substance as monatomic, linear molecule, or nonlinear molecule.
by skalvakota2H
Thu Feb 01, 2018 9:37 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.13
Replies: 5
Views: 216

Re: 9.13

This question was simply poorly worded, because ideal conditions for a gas does not imply the number of moles. If it were standard conditions, then typically the amount of gas would ideally be 1 mol. However, ideal conditions simply pertain to abiding the ideal gas law.
by skalvakota2H
Thu Feb 01, 2018 9:25 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.7
Replies: 3
Views: 122

Re: 9.7

The change in molar internal energy of a monatomic ideal gas at a temperature T is (3/2)*deltaT. So, when calculating the molar heat capacity at constant volume, which is deltaU/deltaT, the quotient is (3/2)*T. Since Cv is (3/2)*T, and Cp=Cv+R, Cp=(5/2)*T. We substitute this equation in for C in the...
by skalvakota2H
Wed Jan 31, 2018 8:26 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.9
Replies: 3
Views: 153

Re: 9.9

Internal energy is simply the total store of energy in a system, which is associated with the random and disordered motion of molecules. On the other hand, temperature measures how much the molecules of a substance are moving. Thus, internal energy is a state function that is dependent on temperatur...
by skalvakota2H
Sat Jan 27, 2018 2:09 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy Units
Replies: 2
Views: 91

Re: Entropy Units

Entropy is simply energy divided by temperature, which yields the unit of Joules per Kelvin (J)*(K^-1).

Note that another property is the entropy of a pure substance, which is given by entropy per unit amount of substance. The unit for this is given by J*(K^-1)*(mol^-1).
by skalvakota2H
Sat Jan 27, 2018 2:02 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: 9
Views: 316

Re: Perfect Crystal

A perfect crystal is a substance in which all the molecules are lined up perfectly, so there are no planar imperfections. Nothing within the crystal is moving, so the arrangement cannot be altered. This implies that at ground state, a perfect crystal would have a degeneracy of 1, or W=1; subsequentl...
by skalvakota2H
Sat Jan 27, 2018 1:55 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneous Reactions [ENDORSED]
Replies: 2
Views: 59

Re: Spontaneous Reactions [ENDORSED]

One way to determine this would be to observe if the entropy of the system increases. This is because all processes naturally seek to increase in entropy. In the case that the entropy decreases, this means that the process could not have occurred in the real world without intervention. Thus, spontan...
by skalvakota2H
Wed Jan 17, 2018 11:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Extensive vs. Intensive
Replies: 3
Views: 123

Re: Extensive vs. Intensive

An extensive property is a property that does depend on the size/extent of the sample. On the other hand, an intensive property is independent of the size of the sample. For example, volume is an extensive property and temperature is intensive. It may prove useful to know that these two are physical...
by skalvakota2H
Wed Jan 17, 2018 11:30 pm
Forum: Calculating Work of Expansion
Topic: 8.3 Homework
Replies: 4
Views: 223

Re: 8.3 Homework

Consider how work is equal to -P∆V. The change in volume of the pump is negative since the pump is being depressed. So algebraically, when substituting a negative value for deltaV, the sign for work will be positive, hence implying that work is being done. Conceptually, the work is positive because ...
by skalvakota2H
Wed Jan 17, 2018 11:20 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: U and H
Replies: 3
Views: 210

Re: U and H

Delta U is the change in the internal energy of the system. In the piston model, when there is expansion energy, the system is doing work on the surroundings which causes a positive increase in volume, thus yielding w= -PΔV since the system lost energy when expanding. As a result, delta U = q-PΔV. H...
by skalvakota2H
Sun Jan 14, 2018 11:50 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: reaction enthalpies
Replies: 3
Views: 118

Re: reaction enthalpies

The sign does change in a reverse reaction. The reasoning is that since enthalpy is a state function, the energy required to push a forward reaction to its products would be directly reversed to push it back to its reactants.
by skalvakota2H
Wed Jan 10, 2018 10:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question about today's lecture problem?
Replies: 3
Views: 135

Re: Question about today's lecture problem?

Given that nitrogen dioxide formation is a multi-step reaction, this means that in order to achieve the overall reaction there will be intermediate steps. In this case, NO (g) is a product of the first reaction but a reactant of the second reaction; thus, NO acts as an intermediate, and since the am...
by skalvakota2H
Wed Jan 10, 2018 9:54 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 2
Views: 154

Re: Phase Changes

Yes, given that the enthalpies are organized into a table, this means that these values must be given at a specific temperature. Hence, we can assume that the reactions will be paired with enthalpies at 25 degrees Celsius.
by skalvakota2H
Thu Dec 07, 2017 12:00 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Relative Acidity Concept Question
Replies: 4
Views: 237

Re: Relative Acidity Concept Question

Atoms with higher electronegativity will be less inclined to share its electrons with a proton. Thus, increasing electronegativity of an atom will decrease basicity, and weaker bases have stronger conjugate acids. Another way to think about this is that with increasing electronegativity, the H-A bon...
by skalvakota2H
Wed Dec 06, 2017 11:46 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: pKa and pH in strong and weak acids [ENDORSED]
Replies: 1
Views: 160

Re: pKa and pH in strong and weak acids [ENDORSED]

The higher the Ka value is, the more protons are donated by the acid, which means the acid is stronger and then pKa value will be lower. Consequently, since the acid is stronger, it will also have a lower pH value. Thus, we can draw a direct relationship.
by skalvakota2H
Tue Nov 28, 2017 9:49 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE Box
Replies: 1
Views: 243

Re: ICE Box

The first equation has 2 molecules of PCl3 as product, while the second equation has 1 molecule of PCl3 as reactant. However, we notice that the third and final equation is the overall reaction, and PCl3 is neither a reactant nor product. Hence, this implies that PCl3 is an intermediate and must be ...
by skalvakota2H
Tue Nov 28, 2017 9:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Box Question
Replies: 1
Views: 124

Re: ICE Box Question

You are only allowed to assume that the initial concentration/pressure of the products is equal to zero. Since the reaction proceeds only when there exists a reactant, the reactant will never have an initial concentration/pressure of zero. However, if the initial concentration/pressure of the reacta...
by skalvakota2H
Tue Nov 21, 2017 9:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K and Q
Replies: 2
Views: 163

Re: K and Q

Think of K as the equilibrium constant, and equilibrium is the final stage of the reaction. Thus, K describes the final concentrations of products and reactants. On the other hand, Q is simply a reaction quotient, which means the expression is a relative ratio of products and reactants at a given in...
by skalvakota2H
Tue Nov 21, 2017 9:17 pm
Forum: *Crystal Field Theory
Topic: Coordination Complex
Replies: 2
Views: 579

Coordination Complex

How does the CFT help predict the color of a coordination complex? It seems the color is drastically impacted by the ligands.
by skalvakota2H
Thu Nov 16, 2017 10:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle answers
Replies: 2
Views: 133

Re: Bond Angle answers

I believe we will not need to know specific bond angles when there are lone pairs. The interaction between a lone pair and bond pair, which is a repulsion, changes the bond angle to a lower value, but we cannot be certain to what degree this change will be. As a result, all we can state is that the ...
by skalvakota2H
Thu Nov 16, 2017 10:44 pm
Forum: Hybridization
Topic: Lone pairs effect hybridization
Replies: 3
Views: 143

Re: Lone pairs effect hybridization

Yes, the lone pairs do count as an electron group towards the hybridization of the central atom since hybridization is based on electron density, which consists of the bonds and lone pairs. As for atoms with four regions of electron density, the central atom would be sp3 hybridized. Once the number ...
by skalvakota2H
Sun Nov 12, 2017 10:28 am
Forum: Coordinate Covalent Bonds
Topic: Ionic and Covalent Bonds
Replies: 2
Views: 313

Re: Ionic and Covalent Bonds

An ionic bond is formed between a metal and nonmetal, and since the nonmetal is more electronegative, the nonmetal will take the electrons from the metal. This produces an electrostatic attraction between oppositely charged ions in a compound. A covalent bond is formed between two nonmetals, which i...
by skalvakota2H
Sun Nov 12, 2017 10:12 am
Forum: Dipole Moments
Topic: Dipole Moments
Replies: 2
Views: 162

Re: Dipole Moments

Dipole moments arise from a difference in electronegativity, and the atoms in a molecule share the electrons unequally. As a result, the atoms involved in a covalent bond will gain either a partially positive or partially negative charge. This establishes a dipole that separates the charges. Dipoles...
by skalvakota2H
Sun Nov 05, 2017 11:09 am
Forum: Resonance Structures
Topic: HW Problem 3.95
Replies: 1
Views: 149

Re: HW Problem 3.95

"H2C" is merely the same as "CH2", except the first is a way to show placement of the hydrogens. Since the bonds are not on hydrogen, it becomes easier to write it as H2C-C to show that the bonds are in fact between carbon. It may be preferable to keep your answer when writing ou...
by skalvakota2H
Sun Nov 05, 2017 10:59 am
Forum: Resonance Structures
Topic: Homework Question 3.45
Replies: 1
Views: 139

Re: Homework Question 3.45

Given that the Cl atom already has 7 valence electrons, and 6 of those are lone pairs, the Cl atom has only one available valence electron for bonding. This means that chlorine is only able to form one bond, which means there can only be a single bond and not a double bond between N and Cl atoms. Th...
by skalvakota2H
Sat Oct 28, 2017 10:35 pm
Forum: Resonance Structures
Topic: Resonance vs. Isomers [ENDORSED]
Replies: 3
Views: 358

Re: Resonance vs. Isomers [ENDORSED]

An isomer refers to a molecule with the same molecular formula but different chemical structure, whereas a resonance structure is when more than one Lewis structure can be drawn for the molecule. The key difference between these two is that different chemical structures is a result of rearranging th...
by skalvakota2H
Sat Oct 28, 2017 10:31 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2.85
Replies: 5
Views: 220

Re: 2.85

Typically, as the occupied energy levels increase in principle quantum number, the energies move closer together, which implies that the energy is dependent on the number of electrons in the level. However, with transition metals, this does not happen when the electrons occupy high energy levels. He...
by skalvakota2H
Sat Oct 28, 2017 3:00 pm
Forum: Significant Figures
Topic: 300 vs 300. [ENDORSED]
Replies: 8
Views: 551

Re: 300 vs 300. [ENDORSED]

Yes, the zeros in 300 are not considered for significant figures but merely space holders, which gives 300 only 1 significant figure. By adding the decimal at the end, the zeros serve as additional measurement decisions which makes the zeros significant, which gives 300. 3 significant figures; note ...
by skalvakota2H
Sun Oct 22, 2017 10:56 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: s-electrons and p-electrons [ENDORSED]
Replies: 2
Views: 181

Re: s-electrons and p-electrons [ENDORSED]

The idea is that since s-electrons do not have a node at the nucleus as opposed to p-electrons with nodes. This difference in shape allows for more electron penetration by the s-electrons. As a result, this decreases the shielding of the s-electrons, and getting closer to the nucleus adds more nucle...
by skalvakota2H
Sun Oct 22, 2017 10:39 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: expected electron configuration of chromium [ENDORSED]
Replies: 3
Views: 253

Re: expected electron configuration of chromium [ENDORSED]

Chromium acts like an exception in the sense that 3d5 is a more stable configuration than 3d4, the reason being that an exactly half filled sub-shell is partially full is more stable than a partially sub-shell. As a result, an electron from the 4s orbital is excited and rises to the 3d orbital.
by skalvakota2H
Sat Oct 14, 2017 10:16 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: H Equation [ENDORSED]
Replies: 6
Views: 370

Re: H Equation [ENDORSED]

With multi-electron atoms, they are characterized by equations used to describe wavelengths that are unique from hydrogen, so using the Rydberg formula for these atoms will yield an incorrect value. As far as I believe this class is concerned, we will only be working with the hydrogen atom as it onl...
by skalvakota2H
Sat Oct 14, 2017 10:08 pm
Forum: Properties of Light
Topic: How to use the Rydberg Formula? [ENDORSED]
Replies: 6
Views: 401

Re: How to use the Rydberg Formula? [ENDORSED]

Since the Rydberg formula is essentially a change equation describing the change in energy from one energy level to another, one will always calculate the difference as final minus initial. This is one way to remember that in the parenthesis, n2 is the final energy level for the electron.
by skalvakota2H
Tue Oct 03, 2017 9:48 pm
Forum: SI Units, Unit Conversions
Topic: Do we need to memorize unit conversions? [ENDORSED]
Replies: 9
Views: 1509

Re: Do we need to memorize unit conversions? [ENDORSED]

Other conversions that may prove useful include:
1000mL = 1L, for volume analysis
1000 g = 1kg for mass analysis

Knowing the difference will make converting units easier when doing dimensional analysis.
by skalvakota2H
Tue Oct 03, 2017 9:29 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7581
Views: 1013775

Re: Post All Chemistry Jokes Here

Really, all the periodic table jokes argon?
I don't zinc so.

Go to advanced search