Search found 73 matches

Thu Mar 14, 2019 10:32 am
Forum: Zero Order Reactions
Topic: Zero order
Replies: 10
Views: 684

Re: Zero order

The order of the reaction just shows if the rate of the reaction is dependent on the concentrations. Thus, if one reactant is zero order, that means the concentration of that reactant does not affect the rate of reaction.
Thu Mar 14, 2019 10:29 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: rate of disappearance
Replies: 3
Views: 126

Re: rate of disappearance

We have to consider the rate of disappearance for the reactants so I think I would use the mol-to-mol ratio to calculate how much reactant disappeared.
Thu Mar 14, 2019 1:40 am
Forum: General Rate Laws
Topic: Rate Law
Replies: 1
Views: 80

Re: Rate Law

You would have to use the half life formula for a first order reaction. You could also use it for parts a and b but it may be easier to just calculate how many half-lives elapsed.
Wed Mar 06, 2019 11:26 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate-Controlling Step
Replies: 3
Views: 134

Re: Rate-Controlling Step

The slowest step is the rate-determining step.
Mon Mar 04, 2019 8:35 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Concentration cells
Replies: 6
Views: 368

Re: Concentration cells

A concentration cell is a type of galvanic cell in which the two half-cells are made up of the same type of solution, only different in concentration. Also, the standard cell potential is equal to zero.
Mon Mar 04, 2019 4:51 pm
Forum: General Rate Laws
Topic: K
Replies: 3
Views: 136

Re: K

A change in temperature or concentration would affect the rate constant.
Tue Feb 26, 2019 11:46 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: inert electrode?
Replies: 1
Views: 52

Re: inert electrode?

An inert electrode is not part of the redox reaction but is needed to conduct the electrons. Use an inert electrode when there are no other solid conducting metals.
Tue Feb 26, 2019 11:45 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Stoichiometric Coefficients in Cell Diagrams
Replies: 2
Views: 86

Re: Stoichiometric Coefficients in Cell Diagrams

Cell diagrams only have the cathode and anode substances. The anode are on the left and the cathode is on the right because the cell diagram is meant to follow the flow of electrons.
Tue Feb 26, 2019 11:44 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy Vs. Other energies
Replies: 1
Views: 63

Re: Gibbs Free Energy Vs. Other energies

Gib's free energy is the maximum amount of reversible work that can be done. All free energy in this course refers to Gibb's Free Energy.
Wed Feb 20, 2019 12:48 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: O2
Replies: 5
Views: 176

Re: O2

The energy of formation for elements is zero because that is the naturally occurring compound in standard conditions.
Wed Feb 20, 2019 12:47 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta Srxn
Replies: 4
Views: 560

Re: Delta Srxn

To find the change in entropy, subtract the molar entropy of the products from the reactants.
Wed Feb 20, 2019 12:47 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta H
Replies: 5
Views: 223

Re: Delta H

Change in enthalpy alone does not determine the spontaneity of the reaction. It also depends on the change in entropy and temperature.
Tue Feb 12, 2019 10:00 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: strong and weak acids
Replies: 5
Views: 412

Re: strong and weak acids

Solutions of weak acids have a higher pH value than solutions of strong acids because it has a lower concentration of hydronium ions, so it is less acidic.
Tue Feb 12, 2019 9:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: practice midterm question
Replies: 3
Views: 137

Re: practice midterm question

This question is a version of Hess' Law except that the question does not explicitly state each equation. Thus, you need to write out each of the equations and subsequently manipulate them and their respective enthalpy to calculate the overall enthalpy.
Tue Feb 12, 2019 9:56 pm
Forum: Calculating Work of Expansion
Topic: when do I use 3/2R??
Replies: 4
Views: 202

Re: when do I use 3/2R??

You would use (3/2)R to calculate the heat capacity, Cvm, of a monoatomic gas when it is at constant volume. You would use (5/2)R to calculate the heat capacity, Cpm, of a gas at constant pressure.
Wed Feb 06, 2019 1:10 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Ideal Gas
Replies: 3
Views: 166

Re: Ideal Gas

We assume gases to be ideal gases for the sake of calculations.
Ideal gases take up no volume and have interactions with other molecules that are insignificant.
Wed Feb 06, 2019 1:05 am
Forum: Phase Changes & Related Calculations
Topic: Heating Curve
Replies: 4
Views: 178

Re: Heating Curve

The heating curve would have a smaller slope because the substance's high heat capacity means that it would be able to absorb more energy for each increase of one degree in temperature.
Wed Feb 06, 2019 1:03 am
Forum: Administrative Questions and Class Announcements
Topic: negative and positive entropy
Replies: 3
Views: 198

Re: negative and positive entropy

Negative entropy means that the system has become more disordered. Positive entropy means that the system has become more ordered.
Sun Feb 03, 2019 2:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Why Bond Enthalpies are the least accurate
Replies: 3
Views: 292

Re: Why Bond Enthalpies are the least accurate

Bond enthalpies are the averages of many bonds and are calculated under standard conditions. Thus, it can be slightly less accurate than the other methods.
Sun Feb 03, 2019 2:11 pm
Forum: Phase Changes & Related Calculations
Topic: Steam resulting in burns?
Replies: 6
Views: 257

Re: Steam resulting in burns?

Steam at 100 degrees releases a lot more heat and energy than boiling water at 100 degrees so it would be much more painful and harmful
Sun Feb 03, 2019 2:10 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter
Replies: 6
Views: 183

Re: Calorimeter

I think we will need to know how to solve calculations involving calorimetry.
Tue Jan 29, 2019 2:51 pm
Forum: Calculating Work of Expansion
Topic: reversible process
Replies: 3
Views: 130

Re: reversible process

R is a constant so it is always the same. There are different units though so the constant can change based on that. Pay attention to the units given in the problems
Tue Jan 29, 2019 2:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sig Figs with Enthalpy
Replies: 4
Views: 177

Re: Sig Figs with Enthalpy

Apply sig figs to enthalpy as usual.
Tue Jan 29, 2019 2:49 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeters
Replies: 3
Views: 130

Re: Calorimeters

I think it is a good idea to know how to solve calorimetry problems
Tue Jan 29, 2019 2:47 pm
Forum: Phase Changes & Related Calculations
Topic: Test #1
Replies: 11
Views: 390

Re: Test #1

I think we should be getting the test back during discussion so we can study it for the midterm
Wed Jan 23, 2019 8:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5% Rule
Replies: 5
Views: 237

Re: 5% Rule

The 5% ionization approximation can be applied to any K calculation as long as K is less that 10^-3
Wed Jan 23, 2019 8:17 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Strength of acids based on Ka and pKa
Replies: 4
Views: 485

Re: Strength of acids based on Ka and pKa

I agree with all the previous responses. The smaller the pKa, the larger the Ka, which means the stronger the acid. The same is also true for bases. The smaller the pKb, the larger the Kb, which means the stronger the base.
Wed Jan 23, 2019 8:15 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Volume and Le Chatelier's Principle
Replies: 5
Views: 196

Re: Volume and Le Chatelier's Principle

If there are the same number of gas moles on both sides of the equation, then the reaction would not shift to favor either direction.
Wed Jan 23, 2019 8:13 pm
Forum: Phase Changes & Related Calculations
Topic: Water heating curve
Replies: 7
Views: 264

Re: Water heating curve

When water is undergoing a change from solid to liquid or liquid to gas, all of the heat supplied during that time is used to break the bonds. Thus, the temperature only increases as the solid, liquid, or vapor continues to heat.
Tue Jan 15, 2019 11:25 pm
Forum: General Science Questions
Topic: SIG FIGS
Replies: 5
Views: 496

Re: SIG FIGS

When considering sig figs for pH, begin counting the number of significant numbers after the decimal. This is because the pH of 1-14 is not based on error
Tue Jan 15, 2019 11:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Aqueous solution
Replies: 2
Views: 107

Re: Aqueous solution

Only aqueous solutions and gases are included in the calculation of the equilibrium constant.
Tue Jan 15, 2019 11:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Hydrofluoric Acid
Replies: 3
Views: 134

Re: Hydrofluoric Acid

Hydrofluoric acid is a weak acid because it does not completely dissociate in water.
Sat Jan 12, 2019 3:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: partial pressures vs concentrations
Replies: 4
Views: 102

Re: partial pressures vs concentrations

It usually depends on the units that are given. If the reactants and products are all gases, then Kp can be used. However, it still may be easier to first calculate Kc because the question may provide numbers in terms of moles and liters.
Sat Jan 12, 2019 3:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibria Changes
Replies: 3
Views: 105

Re: Equilibria Changes

Changing the concentration of reactants or products will not change the K value because the change will either result in more reactants or products being formed to bring the reaction back to equilibrium.
Sat Jan 12, 2019 3:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating K
Replies: 4
Views: 108

Re: Calculating K

Always use equilibrium concentrations to calculate K because K is the equilibrium constant.
Sat Jan 12, 2019 3:12 pm
Forum: Ideal Gases
Topic: Notation [ENDORSED]
Replies: 5
Views: 226

Re: Notation[ENDORSED]

Brackets would denote concentration. Therefore, it would be a better idea to use either parenthesis or nothing at all for partial pressure to minimize confusion.
Sat Dec 08, 2018 1:24 pm
Forum: Bronsted Acids & Bases
Topic: Stronger Acid
Replies: 1
Views: 95

Re: Stronger Acid

Compare it based on the resulting anion stability. Since Cl is more electronegativity, it will help share the -1 formal charge on the oxygen, resulting in a decreased formal charge and more stable anion. So HOCl is the stronger acid.
Sat Dec 08, 2018 1:22 pm
Forum: Naming
Topic: memorizing complexes?
Replies: 2
Views: 110

Re: memorizing complexes?

I think it is a good idea to know everything on his coordination compounds table.
Sat Dec 08, 2018 1:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 7
Views: 335

Re: Polarity

Polar bonds are when there is a difference in electronegativity between two atoms sharing a pair of electrons. The more electronegative atom pulls the electrons slightly closer, resulting in polarity.
Mon Dec 03, 2018 1:21 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Calculating pH
Replies: 3
Views: 124

Re: Calculating pH

I think we will mostly be calculating the pH from the hydronium ion concentration. The pOH can then be calculated by subtracted the pH from 14. With the pOH, we can solve backwards for the concentration of hydroxide ions.
Mon Dec 03, 2018 1:19 pm
Forum: Amphoteric Compounds
Topic: Amphoteric Oxides
Replies: 1
Views: 83

Re: Amphoteric Oxides

The band of amphoteric oxides is not strictly adhered to the band of metalloids. Water is also an important amphoteric oxide,
Mon Dec 03, 2018 1:17 pm
Forum: Lewis Acids & Bases
Topic: Lewis vs. Bronsted
Replies: 5
Views: 755

Re: Lewis vs. Bronsted

In the Bronsted definition, an acid is a proton donor and a base is a proton acceptor.

in the Lewis definition, the acid is an electron acceptor and the base is an electron donor.

Just remember that one has to do with protons and the other with electrons.
Mon Dec 03, 2018 1:16 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Conjugate
Replies: 2
Views: 125

Re: Conjugate

The conjugate seesaw explains the strength of acids and bases in relation to its conjugate acids or bases. A strong acid will translate to a weaker conjugate base. A weak acid will translate to a stronger conjugate base. A strong base will translate to a weaker conjugate acid. A weak base will trans...
Mon Dec 03, 2018 1:15 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Ka Calculations
Replies: 3
Views: 140

Re: Ka Calculations

I do not think we will be asked to calculate pKa because it is merely a way to represent the Ka. We will definitely be asked to calculate pH.
Mon Dec 03, 2018 1:14 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Comparing Weak vs. Strong Acids and Bases
Replies: 3
Views: 158

Re: Comparing Weak vs. Strong Acids and Bases

The main difference between strong and weak acids or bases is in the degree of dissociation. Strong acids completely ionize, releasing all the hydrogen ions. Weak bases, only partially ionize. It is a good idea to memorize the 7 strong acids and the 7 strong bases.
Sun Nov 25, 2018 12:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shapes Not covered in Lecture
Replies: 10
Views: 417

Re: Shapes Not covered in Lecture

It is probably a good idea to know all of the shapes and how each one comes to be based on the regions of electron density and number of lone pairs. Creating a chart might be helpful with this.
Sun Nov 25, 2018 12:20 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Distinguishing between the different intermolecular forces
Replies: 9
Views: 416

Re: Distinguishing between the different intermolecular forces

If a molecule has a hydrogen that is bonded to N, O, or F and N, O, or F has lone pairs, then that molecule likely has hydrogen bonding
Sun Nov 25, 2018 12:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 6
Views: 190

Re: Polarity

Just because a molecule has lone pairs does not mean that it is necessarily polar. It more depends on the where the lone pairs are and how the bonds are placed, if they cancel or not. Think of it as vectors pulling the molecule in opposite directions.
Fri Nov 16, 2018 12:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Distance from Central Atom
Replies: 8
Views: 208

Re: Distance from Central Atom

The shaded and hatched wedges are just there to help distinguish that the bonds are existing in three dimensions. A shaded wedge indicates that the bond is coming out of the plane while a hatched wedge indicates that the wedge is extending back into the plane.
Fri Nov 16, 2018 12:35 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability
Replies: 3
Views: 194

Re: Polarizability

Polarizability corresponds with the interaction between electrons and the nucleus. The less electrons, the stronger the interaction between those electrons and the nucleus. These electrons would be held tightly and have low polarizability because the interaction between those electrons and the nucle...
Fri Nov 16, 2018 12:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear for AX2E3
Replies: 2
Views: 114

Re: Linear for AX2E3

The three lone pairs are in the equatorial plane so the overall shape would be linear.
Sun Nov 11, 2018 5:54 pm
Forum: Coordinate Covalent Bonds
Topic: coordinate covalent bond
Replies: 5
Views: 504

Re: coordinate covalent bond

A coordinate bond is formed when one atom provides both electrons for the shared pair with another atom that is lacking such a pair. The two electrons derive from the same atom.
Sun Nov 11, 2018 5:52 pm
Forum: Sigma & Pi Bonds
Topic: Sigma vs. Pi Bonds
Replies: 3
Views: 152

Re: Sigma vs. Pi Bonds

A sigma bond is the first bond. Every bond after that is a pi bond. A sigma bond would let the molecule be rotated around the bond.
Sat Nov 10, 2018 8:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Drawing Lewis Structures with VSPER
Replies: 5
Views: 227

Re: Drawing Lewis Structures with VSPER

I think drawing it either way would be fine as long as you specify that the molecule is trigonal planar and the bond angle is 120 degrees. Drawing it in its actual position would be a good way to visualize the bond angle though!
Sat Nov 10, 2018 7:39 pm
Forum: Bond Lengths & Energies
Topic: Bond Lengths
Replies: 5
Views: 333

Re: Bond Lengths

Usually, we would be asked to find the bond length if there is some sort of resonance. There is no need to memorize any numbers. For example, the question will give the bond length for the single bond. We can determine that the double bond is shorter. If there is resonance and we are given the singl...
Sat Nov 10, 2018 7:38 pm
Forum: Dipole Moments
Topic: Hydrogen Bonds
Replies: 20
Views: 565

Re: Hydrogen Bonds

Hydrogen bonding is the strongest intermolecular force, but it is still weaker than a covalent or ionic bond. Hydrogen bonds are responsible for holding together DNA, proteins, and other macromolecules and the high melting and boiling point of water.
Sat Nov 03, 2018 7:10 pm
Forum: Trends in The Periodic Table
Topic: Effective Nuclear Charge
Replies: 5
Views: 218

Re: Effective Nuclear Charge

The effective nuclear charge increases across the period because of an increase in positive nuclear charge with no accompanying increase in number of electron shells. The effective nuclear charge decreases down a group because the greater size causes a weaker net attraction.
Sat Nov 03, 2018 7:07 pm
Forum: Lewis Structures
Topic: Memorizing chemical formulas from their names?
Replies: 3
Views: 151

Re: Memorizing chemical formulas from their names?

I think it is a good idea to know some of the more common polyatomic ions such as ammonia, hydroxide, and sulfate. If it is more complicated, it might be given.
Sat Nov 03, 2018 7:05 pm
Forum: Student Social/Study Group
Topic: Sig Figs on Midterm
Replies: 13
Views: 797

Re: Sig Figs on Midterm

I think significant figures will be more important on this test. Pay attention to the question and use the least number of significant figures. One point will probably be docked for each significant figure mistake
Sat Nov 03, 2018 5:57 pm
Forum: Lewis Structures
Topic: Lewis Acids and Bases
Replies: 5
Views: 153

Re: Lewis Acids and Bases

A Lewis acid accepts a pair of electrons while a Lewis base donates a pair of electrons
Sat Oct 27, 2018 8:47 pm
Forum: Lewis Structures
Topic: Polyatomic Ions
Replies: 3
Views: 78

Re: Polyatomic Ions

It may be a good idea to know a few of the basic ones, such as sulfate and ammonium. Otherwise, I think they will be provided or stick to the common ones.
Sat Oct 27, 2018 8:44 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 11
Views: 386

Re: Midterm

The midterm will cover the high school review of chemistry from the first test and the Quantum Chemistry that we are learning now and whatever we cover before the midterm.
Sat Oct 27, 2018 8:42 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Spin Number
Replies: 5
Views: 197

Re: Magnetic Spin Number

They can exist in different orbitals. Two electrons cannot have the same exact four quantum numbers. The fourth number dictates the spin of the electron.
Sat Oct 27, 2018 8:39 pm
Forum: Lewis Structures
Topic: Periodic Table Trends
Replies: 3
Views: 65

Re: Periodic Table Trends

Electron affinity is the energy that is released when an electron is added to an atom. Electronegativity is the atom's tendency to attract an electron in a shared bond. The two terms are similar, but different.
Thu Oct 18, 2018 2:58 pm
Forum: *Shrodinger Equation
Topic: dz orbital
Replies: 2
Views: 79

Re: dz orbital

The cone itself is a nodal plane because the probability of locating an electron in that plane is zero.
Thu Oct 18, 2018 2:44 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbital Interaction
Replies: 2
Views: 91

Re: Orbital Interaction

The different axes are referring to the nodal planes of the different electron orbitals. The nodal planes are where there is zero probability of finding an electron.
Thu Oct 18, 2018 2:42 pm
Forum: *Shrodinger Equation
Topic: Schrodinger Equation
Replies: 2
Views: 53

Re: Schrodinger Equation

Since we won't be doing actual calculations with Schrodinger's Wave Function Equation, I think we just need to understand how it describes quantum mechanical behavior.
Thu Oct 11, 2018 6:34 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 3
Views: 69

Re: Photoelectric Effect

The electrons will descend one energy level at a time since it is quantized. Thus, the energy levels are discrete and not continuous
Thu Oct 11, 2018 6:31 pm
Forum: Empirical & Molecular Formulas
Topic: Is it possible for the Empirical and Molecular formula to be the same? [ENDORSED]
Replies: 8
Views: 419

Re: Is it possible for the Empirical and Molecular formula to be the same?[ENDORSED]

The empirical formula and the molecular formula can be the same! It just means that the molecular formula is already in the simplest form. This can be verified if the mass of the empirical formula is the same as the molar mass of the compound.
Thu Oct 11, 2018 6:28 pm
Forum: Properties of Light
Topic: Threshold Energy
Replies: 11
Views: 292

Re: Threshold Energy

Basically, a metal's threshold energy is the minimum amount of energy that is needed an electron to be ejected from the metal. Each photon needs to have this energy in order for an electron to be ejected.
Thu Oct 04, 2018 12:34 am
Forum: Significant Figures
Topic: Sig Figs
Replies: 6
Views: 211

Re: Sig Figs

400.00 and 400.0 do not have the same number of sig figs because 400.00 if more accurate to a hundredth place than 400.0
Thu Oct 04, 2018 12:32 am
Forum: Significant Figures
Topic: Decimal point
Replies: 14
Views: 474

Re: Decimal point

125 and 125. have the same number of sig figs! Sometimes it may be confusing if the numbers end in 0. For example 120 and 120.0 have different sig figs because of the decimal in place.
Thu Oct 04, 2018 12:31 am
Forum: Molarity, Solutions, Dilutions
Topic: molarity conversion
Replies: 7
Views: 185

Re: molarity conversion

Yes, ml always has to be converted to liters because the units of molarity is moles/liter. If the units are not in L, the units will not cancel appropriately