Instantaneous rate is the rate of the reaction at a particular time.
Average rate is the rate of the reaction over the time taken to the reaction's completion
Search found 66 matches
- Sat Mar 09, 2019 7:15 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Instantaneous vs Average
- Replies: 11
- Views: 974
- Sat Mar 09, 2019 7:10 pm
- Forum: General Rate Laws
- Topic: Unique Reaction Rates [ENDORSED]
- Replies: 45
- Views: 162371
Re: Unique Reaction Rates [ENDORSED]
The unique reaction rate is defined as the rate of the increase in product concentration or the rate in decrease of product concentration divided by the stoichiometric coefficient.
- Sat Mar 09, 2019 7:08 pm
- Forum: Zero Order Reactions
- Topic: Half Life and k
- Replies: 11
- Views: 1730
Re: Half Life and k
This is because k is associated with how fast a reaction runs. If the reaction runs faster then the amount of time needed for the substance to fall to half its original decreases. Hence, K is inversely proportional to Half life.
- Mon Mar 04, 2019 12:02 am
- Forum: Balancing Redox Reactions
- Topic: oxidizing agent and reducing agent
- Replies: 15
- Views: 1308
Re: oxidizing agent and reducing agent
The oxidizing agent always oxidizes the other substance and gets reduced.
The reducing agent always reduces the other substance and gets oxidized.
The reducing agent always reduces the other substance and gets oxidized.
- Sun Mar 03, 2019 11:59 pm
- Forum: Balancing Redox Reactions
- Topic: Ecell
- Replies: 4
- Views: 456
Re: Ecell
You always flip the anode reaction. You can usually determine the anode reaction by choosing the reaction which has the lowest reduction potential (more negative and less positive)
- Sun Mar 03, 2019 11:58 pm
- Forum: Balancing Redox Reactions
- Topic: Order in Cell diagrams
- Replies: 3
- Views: 503
Re: Order in Cell diagrams
it is always anode then cathode. According to Dr Lavelle, we have to also put states in the following manner- solids on the outside and aqueous in the middle.
- Fri Feb 15, 2019 2:19 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs free energy idea
- Replies: 2
- Views: 279
Gibbs free energy idea
What exactly is Gibbs free energy? (conceptually speaking)
- Fri Feb 15, 2019 2:18 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: using gas constant R
- Replies: 4
- Views: 488
Re: using gas constant R
5/2 R= C when the pressure is constant
3/2 R= C when the volume is constant
3/2 R= C when the volume is constant
- Fri Feb 15, 2019 2:17 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: ΔS=q/t
- Replies: 8
- Views: 903
Re: ΔS=q/t
This can only be said when pressure is constant since q(at constant pressure)= delta H
- Fri Feb 15, 2019 2:17 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs free energy
- Replies: 5
- Views: 479
Re: Gibbs free energy
It tells us about spontaneity of a reaction, work and can be used to calculate the equilibrium constant.
- Fri Feb 08, 2019 2:17 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G units
- Replies: 3
- Views: 2929
Re: Delta G units
G is always in terms of Joules. But the equation G=nFE is molarly dependent. Thus, the units are slightly different. But essentially, the conceptual idea is the same.
- Fri Feb 08, 2019 2:15 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Predicting Spontaneity
- Replies: 4
- Views: 1415
Re: Predicting Spontaneity
Yes. We will have to know how to predict spontaneity based on the values. Sign of the enthalpy change Sign of the entropy change Spontaneity positive (+) positive (+) The reaction is spontaneous at high temperature positive (+) negative (-) The reaction is never spontaneous negative (-) negative (-)...
- Fri Feb 08, 2019 2:11 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneity of Exo and Endo reactions
- Replies: 4
- Views: 877
Re: Spontaneity of Exo and Endo reactions
Yes. But spontaneity is largely dependent on the 3 factors: enthalpy change, entropy change and temperature. Based on the values of each, the gibbs free energy is either positive or negative. Usually, however, exothermic reactions are more likely to be spontaneous because is H is less than 0, and si...
- Sat Feb 02, 2019 10:46 pm
- Forum: Phase Changes & Related Calculations
- Topic: PΔV for solids and liquids
- Replies: 5
- Views: 468
Re: PΔV for solids and liquids
This equation does apply to every system. However, when we consider solids and liquids, change in volume is essentially 0 (Dr. Lavelle described this in lecture). Hence P(V final- V initial) is 0 and does not affect systems with solid and liquids.
- Sat Feb 02, 2019 10:43 pm
- Forum: Phase Changes & Related Calculations
- Topic: Steam vs Boiling Water
- Replies: 10
- Views: 10102
Re: Steam vs Boiling Water
Essentially, boiling water at 100 degrees celcius, becomes steam at 100 degrees celcius when it overcomes the latent heat of vaporization. Hence, when skin is exposed to steam, it absorbs more heat from steam as it fist needs to lose the heat of vaporization and convert back to water at 100 degrees....
- Sat Feb 02, 2019 10:40 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Angles
- Replies: 5
- Views: 511
Re: Bond Angles
Bond formation is exothermic while bond breaking is exothermic. Hence, when bonds are formed, since they release energy, we put a negative sign before the values.
- Sun Jan 27, 2019 3:22 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy Units
- Replies: 7
- Views: 718
Re: Enthalpy Units
It depends on the situation. When considering a free reaction, we consider kJ since that is the exact amount of energy being released or absorbed. But, when we consider the situation where in we are considering a standard reaction (ex: Haber's process for 1 mol of ammonia), then we write kJ mol-1 to...
- Wed Jan 23, 2019 1:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Polyprotic acids
- Replies: 1
- Views: 270
Polyprotic acids
How do we calculate the pH of polyprotic acids with very small second or third Ka values? And how small should they be?
- Wed Jan 23, 2019 1:10 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Strong acids and bases
- Replies: 6
- Views: 558
Re: Strong acids and bases
Yes. Dr. Lavelle gave us a couple in 7a. We should remember those.
- Wed Jan 23, 2019 1:09 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Acidity & Basicity Constants
- Replies: 3
- Views: 254
Re: Acidity & Basicity Constants
No. The values will be given on the test.
- Wed Jan 23, 2019 1:08 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: autoprotolysis
- Replies: 5
- Views: 626
Re: autoprotolysis
No, because 10^-4= Kw at 298K is an experimentally determined value.
- Wed Jan 16, 2019 1:09 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Negative pH
- Replies: 12
- Views: 1475
Re: Negative pH
True. Professor Lavelle referred to these acids as super acids.
- Wed Jan 16, 2019 1:08 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 7
- Views: 453
Re: Le Chatelier's Principle
Le Chatelier's principle states that a system will respond to change in a means to minimize the effect of the change. That means that the system tries to reverse the effect to return to what it was (essentially). For example, increases the concentration of products causes the Q value to increase. To...
- Wed Jan 16, 2019 1:03 pm
- Forum: Ideal Gases
- Topic: K value
- Replies: 8
- Views: 779
Re: K value
Because that would indicate that the products and reactants are in the same ratio. Essentially, in the real world, that would be rare.
- Wed Jan 16, 2019 1:02 pm
- Forum: Ideal Gases
- Topic: Pressure and Temperature [ENDORSED]
- Replies: 2
- Views: 418
Re: Pressure and Temperature [ENDORSED]
As temperature increases, the molecules of gas have more energy and begin striking the walls of a container with higher frequency. Essentially, the molecules exhibit a higher pressure on the container since they attempt to further themselves from each other.
- Wed Jan 16, 2019 1:00 pm
- Forum: Ideal Gases
- Topic: R in PV=nRT
- Replies: 34
- Views: 5847
Re: R in PV=nRT
R is the ideal gas constant 8.314 J/(K mol)
- Wed Jan 16, 2019 12:59 pm
- Forum: Ideal Gases
- Topic: bar or atm
- Replies: 8
- Views: 590
Re: bar or atm
Bar and atm are the same. They can be interchanged.
- Wed Jan 16, 2019 12:58 pm
- Forum: Ideal Gases
- Topic: Using Kc or Kp
- Replies: 13
- Views: 931
Re: Using Kc or Kp
Kp is used when the substances are gaseous. But Kc can be used when the substances are gaseous or aqueous.
- Wed Jan 09, 2019 1:00 pm
- Forum: Ideal Gases
- Topic: Q and K [ENDORSED]
- Replies: 35
- Views: 3010
Re: Q and K [ENDORSED]
No difference. It's the same but K is when equilibrium is achieved. Q is at any point of the reaction.
- Fri Nov 30, 2018 11:12 pm
- Forum: Lewis Acids & Bases
- Topic: solution of weak acids with higher pH
- Replies: 4
- Views: 1418
Re: solution of weak acids with higher pH
Weak acids do not completely dissociate and thus the proton yield is lower. Consequently, the pH is higher than for a strong acid which almost always dissociate completely and yields higher proton concentration.
- Fri Nov 30, 2018 11:10 pm
- Forum: Lewis Acids & Bases
- Topic: Strong Acid
- Replies: 8
- Views: 1124
Re: Strong Acid
Strong acids almost always dissociate completely to yield hydronium ions.
- Fri Nov 30, 2018 11:09 pm
- Forum: Lewis Acids & Bases
- Topic: Determine Lewis Acid
- Replies: 13
- Views: 1600
Re: Determine Lewis Acid
Lewis acids are electron pair acceptors.
- Fri Nov 30, 2018 3:01 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate
- Replies: 3
- Views: 395
Re: Polydentate
It refers to one ligand that can form multiple coordinate bonds with the central metal ion. Ex: EDTA
- Wed Nov 21, 2018 5:07 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Test 3
- Replies: 10
- Views: 959
Re: Test 3
Test 3 covers: End of Bonding from 3.12 (6 Ed.) and from 2D (7 Ed.); and all of Molecular Shape and Structure
- Wed Nov 21, 2018 5:06 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Ethylene bond angle
- Replies: 2
- Views: 233
Re: Ethylene bond angle
Ethylene is formed from a sp2 hybridization of carbon and the arrangement on the orbitals are in the triangular planar. The angles are thus all 120 degrees.
- Wed Nov 21, 2018 5:02 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sigma/Pi bonds
- Replies: 7
- Views: 748
Re: Sigma/Pi bonds
Sigma bonds are formed when orbitals overlap head on, along the bond axis. Pi bonds are formed when the ortibals overlap above and below the bond axis.
- Wed Nov 14, 2018 10:57 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Strengths
- Replies: 5
- Views: 414
Re: Bond Strengths
Ionic bonds are stronger since they are the electrostatic force of attraction between positively and negatively charged ions. Hydrogen bonds are weaker since they are between dipoles (partially charged regions of a molecule).
- Wed Nov 14, 2018 10:55 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Angular Shape
- Replies: 4
- Views: 612
Re: Angular Shape
Angular shape can exist in two forms: 1) 3 regions of electron density (1 lone pair and 2 bonded pairs- Sulfur dioxide)- it has a bond angle of less than 120 (around 117) 2) 4 regions of electron density (2 lone pairs and 2 bonded pairs- dihydrogen monoxide)- it has a bond angle of less than 109.5 (...
- Wed Nov 14, 2018 10:52 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Shape
- Replies: 4
- Views: 394
Re: Molecular Shape
Molecular shape is dependent on the areas of electron density around the central atom. It can be divided into two categories: 1. Bonded pairs (single, double and triple) 2. Lone pairs The repulsion affects the shape further: lone-lone> lone-bonded> bonded-bonded These are the main features that affe...
- Wed Nov 14, 2018 10:50 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 3
- Views: 274
Re: Bond Angles
Bond angles are dependent on the number of lone pairs and bonding pairs around the central atom. Bonding pairs are less repelled by one another than from lone pairs. When we take Methane for example, there are 4 bonding pairs around the carbon and to space themselves out maximally, they form a tetra...
- Sat Nov 10, 2018 8:18 pm
- Forum: Bond Lengths & Energies
- Topic: bond lengths and strengths
- Replies: 9
- Views: 900
Re: bond lengths and strengths
Single bonds are the weakest since only one electron pair is being shared. Thus, the force of attraction between the nucleus and the shared pair is low. However, with double bonds, the area of electron density is much more dense/strong since more number of electrons are being shared and thus the for...
- Sat Nov 10, 2018 8:16 pm
- Forum: Dipole Moments
- Topic: Melting points
- Replies: 5
- Views: 649
Re: Melting points
Hydrogen bonds by definition only form when hydrogen is directly bonded to N, F and O. The electronegativity difference in sulphur and hydrogen is much lower than that of hydrogen and oxygen. Hydrogen sulphide, thus, is less polar and the dipole formed are weaker than in water. Thus, a hydrogen bond...
- Sat Nov 10, 2018 8:13 pm
- Forum: Bond Lengths & Energies
- Topic: Bond Lengths
- Replies: 6
- Views: 551
Re: Bond Lengths
They can only be determined experimentally. However, the relative bond lengths can be determined by the electronegativity differences between the elements participating in the bond (carbon-fluorine bonds have a shorter bond length than carbon-bromine bonds)
- Sat Nov 10, 2018 8:11 pm
- Forum: Electronegativity
- Topic: Electronegativity relationship with Polarizability
- Replies: 3
- Views: 751
Re: Electronegativity relationship with Polarizability
Electronegativity is the tendency of an atom of an element to attract electrons towards itself when bonded. Polarizability is the tendency to be polarized (electrons can be 'distorted' by other atoms) Generally substances with high electronegativity has a tendency to be less polarized (since the ele...
- Sun Nov 04, 2018 7:31 pm
- Forum: Dipole Moments
- Topic: london forces
- Replies: 7
- Views: 821
Re: london forces
Yes, every atom can exhibit london dispersion forces because it is due to the essentially random movement of electrons in an atom resulting in the formation of a temporary dipole.
- Sun Nov 04, 2018 7:30 pm
- Forum: Electronegativity
- Topic: electronegativity vs electron affinity
- Replies: 4
- Views: 435
Re: electronegativity vs electron affinity
Electron affinity is calculated for gaseous atoms (the energy change when an electron is added to the gaseous atom) and its unit is kJ/mol. This is experimentally derived. Electronegativity is the tendency of an atom to attract electrons towards in a bonded state and is for bonded atoms only. It is ...
- Sun Nov 04, 2018 7:28 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Why does PCl5 break the Octet Rule?
- Replies: 8
- Views: 6948
Re: Why does PCl5 break the Octet Rule?
This is because phosphorous can utilize the d orbitals and, thus, has an expanded octet.
- Sun Nov 04, 2018 7:27 pm
- Forum: Ionic & Covalent Bonds
- Topic: Naming Ionic Compounds
- Replies: 5
- Views: 460
Re: Naming Ionic Compounds
Naming works pretty easily. The name of the cation always comes before the name of the anion. Most cations would be the name of the metal (sodium, lithium, calcium, etc.) The name of the anion is variable: Halogens would end in "ide" (fluoride, chloride, bromide, etc) The same applies for ...
- Tue Oct 30, 2018 12:16 pm
- Forum: Significant Figures
- Topic: Exam
- Replies: 6
- Views: 1149
Exam
How do we determine the number of significant figures to use in the exam?
- Tue Oct 30, 2018 12:16 pm
- Forum: Octet Exceptions
- Topic: Structure of HClO3
- Replies: 1
- Views: 2808
Structure of HClO3
How do we draw the lewis structure of HClO3?
- Tue Oct 30, 2018 12:15 pm
- Forum: Octet Exceptions
- Topic: Octet exception chlorine and xenon
- Replies: 1
- Views: 242
Octet exception chlorine and xenon
Why can xenon extend to more number of electrons through expanded octet than chlorine?
- Tue Oct 30, 2018 12:14 pm
- Forum: Sigma & Pi Bonds
- Topic: Strength of bonds
- Replies: 1
- Views: 516
Strength of bonds
Why are sigma bonds stronger than pi bonds?
- Tue Oct 30, 2018 11:06 am
- Forum: Ionic & Covalent Bonds
- Topic: ionization energy
- Replies: 7
- Views: 783
Re: ionization energy
Because the second ionization energy is the removal of the electron from a cation which has a stronger pull on the electron than the neutral atom.
- Sun Oct 21, 2018 11:44 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: h with a line through it?
- Replies: 8
- Views: 1872
Re: h with a line through it?
h bar is h/2pi
- Sun Oct 21, 2018 11:44 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Shielding
- Replies: 5
- Views: 1125
Re: Shielding
Shielding is when electrons in lower energy levels "shielding" or preventing the nuclear charge from reaching electrons in outer shells. Thus, when there are more number of orbitals, there is more shielding on the outer electrons.
- Sun Oct 21, 2018 11:39 pm
- Forum: Properties of Electrons
- Topic: Electron Spin
- Replies: 7
- Views: 849
Re: Electron Spin
There is not much to be known for this course. In each orbital, 2 electrons can exist and they take up opposite spins. They take the values 1/2 and -1/2 since there's 50% chance of up spin and 50% chance of down spin.
- Sun Oct 21, 2018 11:37 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Wave functions
- Replies: 4
- Views: 419
Wave functions
Do we have to know how to solve the wave functions for the orbitals?
- Sun Oct 14, 2018 11:24 pm
- Forum: *Black Body Radiation
- Topic: What exactly is Black Body Radiation?
- Replies: 1
- Views: 508
Re: What exactly is Black Body Radiation?
The black body radiation refers to the idea that a body which absorbs all frequencies of light of the electromagnetic spectrum. It also happens to not only be the ideal absorber of light but the ideal emitter (ex: a star) - emitting light of all frequencies.
- Sun Oct 14, 2018 11:20 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Uncertainty Principle
- Replies: 5
- Views: 405
Re: Uncertainty Principle
The uncertainty principle works on the idea that both the momentum and the location of an electron cannot be known at once. When one is known, the other can be calculated but not known in that point of time. Thus, when we calculate anything regarding the uncertainty, its a range of possibilities (he...
- Sun Oct 14, 2018 11:18 pm
- Forum: Photoelectric Effect
- Topic: SI Unit for Work Function
- Replies: 4
- Views: 1756
Re: SI Unit for Work Function
It would be preferred to stick to Joules since the entire equation focuses on generating the amount of energy needed to for the photoelectric effect.
- Thu Oct 11, 2018 9:36 am
- Forum: Properties of Light
- Topic: Light acts as a wave or not?
- Replies: 10
- Views: 591
Re: Light acts as a wave or not?
Light acts like both a wave and a particle. Depending on the situation, for questions in class, we tend to adopt the wave or particle model which fits a particular explanation.
- Thu Oct 11, 2018 9:34 am
- Forum: Properties of Light
- Topic: Do I need to memorize the Light Spectrum? [ENDORSED]
- Replies: 13
- Views: 900
Re: Do I need to memorize the Light Spectrum? [ENDORSED]
I think it would be advisable to have a general idea, like Dr. Lavelle said, about where a particular wavelength falls.
100-400 nm: UV light
400-700 nm: Visible light
700 nm- 1 mm: Infrared radiation
100-400 nm: UV light
400-700 nm: Visible light
700 nm- 1 mm: Infrared radiation
- Thu Oct 11, 2018 9:31 am
- Forum: Properties of Light
- Topic: Photoelectric effect
- Replies: 4
- Views: 203
Re: Photoelectric effect
Yes. The photon of the incident light must have sufficient energy such that it exceeds or equals the work function. Only then, will the electron have sufficient energy to be ionized and get released to be detected and produce the photoelectric effect.
- Thu Oct 04, 2018 8:54 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Isotopes [ENDORSED]
- Replies: 12
- Views: 1420
Re: Isotopes [ENDORSED]
Isotopes are atoms of the same elements but have different mass numbers or different number of protons!
- Thu Oct 04, 2018 8:52 pm
- Forum: Empirical & Molecular Formulas
- Topic: How many atoms, how many moles are in epsom salts?
- Replies: 2
- Views: 3004
Re: How many atoms, how many moles are in epsom salts?
Epsom salts consist of magnesium sulfate heptahydrate. Write its formula. a) How many atoms of oxygen are in 5.15g of Epsom salts? b) How many formula units of the compound are present in 5.15g? c) How many moles of water molecules are in 5.15 g of Epsom salts? Answers: a) no. of moles of magnesium ...
- Sun Sep 30, 2018 12:45 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Accuracy vs Precision
- Replies: 23
- Views: 2591
Re: Accuracy vs Precision
From an experimental chemistry standpoint, an example of accuracy vs. precision would be: If we conducted an experiment to test the volumes of carbon dioxide released when different concentrations of acid were added to metal carbonates, the study would have- 1. Low accuracy and Low precision if the ...