Search found 58 matches

by Aili Ye 4L
Mon Mar 18, 2019 9:37 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: A in the arrhenius equation
Replies: 2
Views: 326

Re: A in the arrhenius equation

A is the pre-exponential factor, a constant for each chemical equation which shows the frequency of collisions in the correct orientation.
by Aili Ye 4L
Mon Mar 18, 2019 9:35 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: intermediate
Replies: 4
Views: 232

Re: intermediate

Intermediates are form and then used up so they are not part of the overall reaction and therefor rate law as well
by Aili Ye 4L
Mon Mar 18, 2019 9:32 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: zero order reaction
Replies: 2
Views: 163

Re: zero order reaction

The integrated rate for a first order reaction is A= -kt + Ao which is in the form of a linear equation where -k is the slope.
by Aili Ye 4L
Sun Mar 10, 2019 10:32 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: how is kinetics different?
Replies: 17
Views: 278

Re: how is kinetics different?

Thermodynamics deals with the spontaneity of a reaction whereas kinetics deals with the speed of a reaction.
by Aili Ye 4L
Sun Mar 10, 2019 10:21 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: kinetics vs thermodynamics
Replies: 3
Views: 85

Re: kinetics vs thermodynamics

Thermodynamics deals with the spontaneity of a reaction, whereas kinetics deal with the speed of one.
by Aili Ye 4L
Sun Mar 10, 2019 10:06 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Activation Energy
Replies: 7
Views: 245

Re: Activation Energy

Activation energy is the energy needed to turn reactants into products. It is the energy difference between the energy of the reactants and the highest peak of the energy graph.
by Aili Ye 4L
Sun Mar 03, 2019 10:12 pm
Forum: Balancing Redox Reactions
Topic: oxidizing agent and reducing agent
Replies: 15
Views: 211

Re: oxidizing agent and reducing agent

The compound that oxidizes (oxidizing agent) is the one that itself gets reduced, and vice versa.
by Aili Ye 4L
Sun Mar 03, 2019 10:05 pm
Forum: Balancing Redox Reactions
Topic: Writing half reactions
Replies: 7
Views: 140

Re: Writing half reactions

The H+ would be with the Cr2O7 since the oxygen atoms in it are balanced with H20, and the H20 are balanced with H+
by Aili Ye 4L
Sun Mar 03, 2019 10:02 pm
Forum: Balancing Redox Reactions
Topic: Acidic vs basic solutions
Replies: 10
Views: 161

Re: Acidic vs basic solutions

You can balance both initially using H+, but if you are balancing in a basic solution you must add OH- to neutralize the H+
by Aili Ye 4L
Sun Feb 24, 2019 10:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Graphite
Replies: 3
Views: 55

Re: Graphite

It is an inert electrode.
by Aili Ye 4L
Sun Feb 24, 2019 10:36 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating cell potential using cathode and anode values
Replies: 2
Views: 45

Re: Calculating cell potential using cathode and anode values

The standard cell potentials is for reduction. That reduction occurs at the anode so we do not flip the sign.
by Aili Ye 4L
Sun Feb 24, 2019 10:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: inert conductor besides Pt
Replies: 3
Views: 74

Re: inert conductor besides Pt

The other inert conductor is graphite (carbon).
by Aili Ye 4L
Sat Feb 16, 2019 10:22 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: 9.35
Replies: 2
Views: 221

Re: 9.35

Here's a more detailed explanation taken from Lavelle's Chem 14B Solution Manual Errors 6th Edition pdf: "Students are asked to rank the delta S for a series of gases during a temperature change. ∆S = nCv ln(T2/T1) for an isochoric process Gas A (1.00 mol monatomic ideal): ∆S = nCv ln(T2/T1) = ...
by Aili Ye 4L
Sat Feb 16, 2019 10:17 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: n in degeneracy
Replies: 8
Views: 547

Re: n in degeneracy

n is the number of molecules, not atoms, so in this case n would be 1.
by Aili Ye 4L
Sat Feb 16, 2019 10:16 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: How to calculate W
Replies: 9
Views: 326

Re: How to calculate W

W (degeneracy) is calculated by the number of microstates/equal energy conformantions to the power of the number of molecules. S (entropy) is thus equal to the Boltzmann's constant multiplied by lnW.
by Aili Ye 4L
Wed Feb 06, 2019 3:33 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Isochoric
Replies: 4
Views: 83

Re: Isochoric

An isochoric process is a thermodynamic process in which volume is constant.
by Aili Ye 4L
Wed Feb 06, 2019 3:27 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: enthalpy of combustion vs formation
Replies: 3
Views: 78

Re: enthalpy of combustion vs formation

The enthalpy of combustion is the energy released when one mole of a compound is burned in oxygen, whereas the enthalpy of formation is the change in enthalpy when one mole of a substance is formed from its constituent elements in their standard state.
by Aili Ye 4L
Wed Feb 06, 2019 3:21 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ΔH and ΔU
Replies: 6
Views: 130

Re: ΔH and ΔU

The degree symbol means that the reaction is taking place under STP (standard temperature and pressure) conditions.
by Aili Ye 4L
Sat Feb 02, 2019 4:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 6th Edition 8.73
Replies: 2
Views: 68

Re: 6th Edition 8.73

As the other person mentioned, standard enthalpy of formation and bond enthalpy is different. Bond enthalpy cannot be zero since all bonds require energy to break.
by Aili Ye 4L
Sat Feb 02, 2019 4:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: breaking double bonds?
Replies: 6
Views: 88

Re: breaking double bonds?

Double and triple bonds don't have the bond enthalpy equal to double or triple that of a single bond, so you must calculate single and double bond breaks differently.
by Aili Ye 4L
Sat Feb 02, 2019 4:35 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpies
Replies: 5
Views: 74

Re: Enthalpies

Enthalpy is a thermodynamic measure of the total heat of a system. Change in enthalpy is thus changes in internal heat of the system.
by Aili Ye 4L
Fri Jan 25, 2019 3:14 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strength and Weakness
Replies: 4
Views: 248

Re: Strength and Weakness

Look at the Ka, the larger the Ka the more favored the dissociation into H3O+ and the stronger the acid. Or look at pKa- the smaller the pKa the stronger the acid.
by Aili Ye 4L
Fri Jan 25, 2019 3:12 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Number 71 Chapter 12 Homework
Replies: 2
Views: 212

Re: Number 71 Chapter 12 Homework

Na is simply a spectator ion in the reaction and thus isn't necessarily included.
by Aili Ye 4L
Fri Jan 25, 2019 11:33 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test 1
Replies: 9
Views: 173

Re: Test 1

pKw at 25 degrees IS 14.
by Aili Ye 4L
Sat Jan 19, 2019 11:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Arrow
Replies: 7
Views: 133

Re: Equilibrium Arrow

Yes, only weak acids and bases use the equilibrium arrow. Strong acids and bases are considered 100% ionization in water thus only use one arrow
by Aili Ye 4L
Sat Jan 19, 2019 11:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium constant in different temperatures
Replies: 3
Views: 32

Re: Equilibrium constant in different temperatures

This takes into consideration the Chatelier’s principle which states that whenever a system in equilibrium is disturbed the system will adjust itself in such a way that the effect of the change will be reduced or moderated. Increasing or decreasing the temperature will make the system favor either t...
by Aili Ye 4L
Sat Jan 19, 2019 11:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Molar Concentration
Replies: 3
Views: 66

Re: Molar Concentration

No, there isn’t such a thing as “concentration of a single molecule”. You should find the concentration overall of the molecule and take into consideration the stoichiometric coefficients is different reactants and products when calculating unknown concentrations though.
by Aili Ye 4L
Fri Jan 11, 2019 3:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th Edition 5H.3
Replies: 3
Views: 79

Re: 7th Edition 5H.3

Since that equation is the addition of two previous equations whose K eqs are given, the K eq value of the total equation is the product of the two previous Keqs.
by Aili Ye 4L
Fri Jan 11, 2019 3:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: liquids in equilibrium
Replies: 2
Views: 58

Re: liquids in equilibrium

We do not include liquids and solids because by convention the values in the calculation of the K expression change over time. The concentrations of solids and liquids do not change.
by Aili Ye 4L
Fri Jan 11, 2019 3:05 pm
Forum: Ideal Gases
Topic: Reaction Quotient
Replies: 6
Views: 107

Re: Reaction Quotient

We don't include liquids and solids because by convention the values in the K expression change over time, and the concentration of liquids and solids do not change.
by Aili Ye 4L
Sun Dec 09, 2018 12:06 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Final Exam
Replies: 7
Views: 162

Re: Final Exam

I believe we do.
by Aili Ye 4L
Sun Dec 09, 2018 12:03 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Why is trichloroacetic acid stronger than acetic acid?
Replies: 2
Views: 76

Re: Why is trichloroacetic acid stronger than acetic acid?

The three chlorine atoms are more electronegative and thus pull electrons towards it. This weakens the bonds between the O and H and thus this acid would lose an H more easily, making it a stronger acid.
by Aili Ye 4L
Sat Dec 08, 2018 11:44 pm
Forum: Amphoteric Compounds
Topic: water
Replies: 4
Views: 210

Re: water

Double arrows show that the reaction can proceed both forwards or backwards depending on the equilibrium constant.
by Aili Ye 4L
Sun Dec 02, 2018 4:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Square Planar
Replies: 12
Views: 232

Re: Square Planar

The angles are just 90 degrees on the equatorial plane since repulsion from the lone pairs cancel out.
by Aili Ye 4L
Sun Dec 02, 2018 4:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar Molecules
Replies: 12
Views: 184

Re: Polar Molecules

The way I look at it is to envision the shape and look at its symmetry. Usually non-symmetric shapes with lone pairs are polar, and symmetric shapes without lone pairs or have lone pairs that cancel each other out (as in the example of a square planar molecule) are non-polar.
by Aili Ye 4L
Sun Dec 02, 2018 4:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Model
Replies: 5
Views: 121

Re: VSEPR Model

Just refer to the model when answering the question. VSEPR model is just the formula and shape and angles. We should not need to know how to draw it out.
by Aili Ye 4L
Sun Nov 25, 2018 3:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 6
Views: 98

Re: Polarity

Polarity depends on symmetry of the molecule. Sometimes lone pairs can cancel out, such as in the case of AX4E2, which is square planar. Since the lone pairs are directly opposite each other, the repulsion caused by them cancel out, and thus the atoms remain in a symmetrical position.
by Aili Ye 4L
Sun Nov 25, 2018 3:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Trigonal Planar or Trigonal Pyramidal?
Replies: 4
Views: 93

Re: Trigonal Planar or Trigonal Pyramidal?

The structure would be trigonal planar if the lone pair did not exist. But the existence of the lone pair creates repulsion and takes up more space than an atom would and thus this would push the other molecules into a pyramidal shape.
by Aili Ye 4L
Sun Nov 25, 2018 3:34 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar molecules
Replies: 3
Views: 72

Re: Polar molecules

Often, the lone pair can distort the symmetry and will create a polar molecule, but it is not always the case.
by Aili Ye 4L
Sat Nov 17, 2018 4:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Chart
Replies: 3
Views: 73

Re: VSEPR Chart

Thank you!
by Aili Ye 4L
Sat Nov 17, 2018 4:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Square Planar Angles
Replies: 3
Views: 74

Re: Square Planar Angles

The angle remains 90 degrees. The repulsion does not change it.
by Aili Ye 4L
Sat Nov 17, 2018 4:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles
Replies: 5
Views: 80

Re: Bond angles

I may be wrong, but we do not need to know any formulas. The angles we give should be approximate.
by Aili Ye 4L
Wed Nov 07, 2018 2:56 pm
Forum: Bond Lengths & Energies
Topic: Bond length energies
Replies: 3
Views: 73

Re: Bond length energies

The positive charge on the nucleus attracts the extra electrons in the double and triple bonds thus causing a stronger bond.
by Aili Ye 4L
Wed Nov 07, 2018 2:50 pm
Forum: Bond Lengths & Energies
Topic: Triple Bonds Shorter than Double Bonds
Replies: 4
Views: 190

Re: Triple Bonds Shorter than Double Bonds

The positive nucleus exerts a force on the electrons involved in the triple bond, causing the bond to be stronger and the electrons to be closer to the nucleus, meaning a shorter bond.
by Aili Ye 4L
Wed Nov 07, 2018 2:41 pm
Forum: Dipole Moments
Topic: HCl
Replies: 6
Views: 111

Re: HCl

There is an electronegativity difference between the H and Cl atoms. Cl is more electronegative and thus attracts electrons more, causing the dipole.
by Aili Ye 4L
Sun Nov 04, 2018 2:21 pm
Forum: Ionic & Covalent Bonds
Topic: Chemical Bonds
Replies: 5
Views: 145

Re: Chemical Bonds

Chemical bonds form when valence electrons of atoms interact. The type of bond that forms depends on electronegativity.
by Aili Ye 4L
Mon Oct 29, 2018 10:16 am
Forum: Trends in The Periodic Table
Topic: Smallest ionic radius [ENDORSED]
Replies: 6
Views: 183

Re: Smallest ionic radius [ENDORSED]

The more positive charge for the same negative charge on isoelectronic atoms, the stronger the attraction and thus the smaller the radius.
by Aili Ye 4L
Mon Oct 29, 2018 10:13 am
Forum: Trends in The Periodic Table
Topic: Periodic table
Replies: 4
Views: 145

Re: Periodic table

Ionization energy is the amount of energy required to remove the most loosely bound electron from a neutral atom in the gaseous state, whereas electronegativity is the measure of the tendency of an atom to attract a bonding pair of electrons. Ionization energy increases across a period (more protons...
by Aili Ye 4L
Mon Oct 29, 2018 10:06 am
Forum: Trends in The Periodic Table
Topic: Electron affinity
Replies: 3
Views: 108

Re: Electron affinity

Electron affinity is the energy released when an electron is added to a neutral atom in the gaseous state. Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.
by Aili Ye 4L
Fri Oct 26, 2018 4:34 pm
Forum: Ionic & Covalent Bonds
Topic: periodic table
Replies: 4
Views: 90

Re: periodic table

Metals on the left tend to lose electrons, non-metals on the right tend to gain electrons, both try to reach the number of electrons of their closest noble gas.
by Aili Ye 4L
Fri Oct 26, 2018 4:33 pm
Forum: Ionic & Covalent Bonds
Topic: Ground State Electron Configurations
Replies: 7
Views: 101

Re: Ground State Electron Configurations

Argon is the noble gas that comes before Copper, and using its electron configuration we can avoid writing out copper's entire electron configuration. It helps us avoid writing lengthy and often distracting long configurations.
by Aili Ye 4L
Wed Oct 24, 2018 11:12 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg constant in Test 2
Replies: 1
Views: 86

Rydberg constant in Test 2

Do we need to memorize Rydberg's constant for test 2 or will the value be given?
by Aili Ye 4L
Sun Oct 21, 2018 8:09 pm
Forum: Photoelectric Effect
Topic: Kinetic energy
Replies: 4
Views: 86

Re: Kinetic energy

You might have to find the work function, but then the other variables should either be given or can be found, and then work function should be easy to find with the equation.
by Aili Ye 4L
Sun Oct 21, 2018 8:07 pm
Forum: Properties of Electrons
Topic: Electrons - Wave Properties
Replies: 4
Views: 80

Re: Electrons - Wave Properties

All objects have particle and wave properties. Electrons have measurable wavelengths because they have a small mass and the De Broglie wavelength is measured by Plank's constant divided by the mass times velocity. Larger objects have larger masses and thus their wavelengths are very difficult to mea...
by Aili Ye 4L
Sun Oct 21, 2018 8:01 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: h with a line through it?
Replies: 8
Views: 170

Re: h with a line through it?

As the person stated above, h-bar is the same thing as h/2, there is no difference.
by Aili Ye 4L
Sat Oct 13, 2018 8:33 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: diatomic elements
Replies: 12
Views: 769

Re: diatomic elements

Some elements exist as diatomic elements since in their original state, their valence shells are not filled, thus they share electrons between each other and thus fill their shells and achieve a state of lower energy.
by Aili Ye 4L
Sat Oct 13, 2018 8:29 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: MOLARITY
Replies: 17
Views: 621

Re: MOLARITY

Molarity's importance lies in how it defines the concentration of the solution and acting as a measurement of moles of solute per liter of solution. It is a big part of dilution calculations since moles of solute stay the same, so it is easy to calculate the molarity when knowing how much solution w...
by Aili Ye 4L
Sat Oct 13, 2018 8:21 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Avogadro's Constant Definition
Replies: 7
Views: 429

Re: Avogadro's Constant Definition

A mole of H2 would include 6.02x1023 molecules of H2. But that would mean twice that for number of atoms.

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