Search found 69 matches

Fri Mar 15, 2019 11:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt bridge
Replies: 1
Views: 121

Salt bridge

Can someone explain what ions would affect the salt bridge?
Wed Mar 13, 2019 12:39 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Units of k
Replies: 5
Views: 407

Units of k

Can someone show how to derive the units of k for zero, first, and second order reactions?
Wed Mar 13, 2019 12:37 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Catalyst vs. Intermediate
Replies: 8
Views: 260

Catalyst vs. Intermediate

Can someone explain how I would differentiate a catalyst from an intermediate in a reaction?
Wed Mar 13, 2019 12:34 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Does reaction rate mean average reaction rate?
Replies: 3
Views: 188

Re: Does reaction rate mean average reaction rate?

If it says average rate, then it is average. If it just says rate, then they are referring to the instantaneous rate.
Mon Mar 04, 2019 7:05 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Corrosion
Replies: 2
Views: 335

Corrosion

Can someone explain what happens to the electrons during corrosion?
Mon Mar 04, 2019 7:03 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Order of Reaction
Replies: 5
Views: 266

Order of Reaction

Can someone explain the concept of order of reactions? I understand how to find the order based on the rate law, but I don't understand it conceptually. Can someone help me?
Mon Mar 04, 2019 6:59 pm
Forum: Zero Order Reactions
Topic: Order distinction
Replies: 9
Views: 521

Re: Order distinction

When you look at the rate law, you add the exponents of all the concentrations of the reactants.
Mon Mar 04, 2019 6:58 pm
Forum: Zero Order Reactions
Topic: Order distinction
Replies: 9
Views: 521

Re: Order distinction

When you look at the rate law, you add the exponents of all the concentrations of the reactants.
Sun Feb 24, 2019 9:05 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 2
Views: 84

Cell Diagrams

When do we use commas in a cell diagram vs. a horizontal line?
Sun Feb 24, 2019 9:03 pm
Forum: Balancing Redox Reactions
Topic: Balancing redox reactions
Replies: 1
Views: 62

Balancing redox reactions

What role does water play if the original equation has water in the products? Does it just cancel out by adding hydrogens when balancing?
Sun Feb 24, 2019 8:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Graphite
Replies: 3
Views: 106

Graphite

What role does graphite have in a galvanic cell?
Sun Feb 24, 2019 8:58 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions
Replies: 1
Views: 70

Balancing Redox Reactions

Can someone go through the steps to balance a redox reaction? Which elements do I look at first, which part do I balance first?
Thank you!
Sun Feb 24, 2019 8:55 pm
Forum: Balancing Redox Reactions
Topic: Oxidation numbers
Replies: 1
Views: 58

Oxidation numbers

For the compound C2H5OH, what is the oxidation state of C? I thought it was 2+, but the solutions manual is saying it is 2-?
Thu Feb 21, 2019 12:20 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Stable vs Unstable
Replies: 2
Views: 89

Stable vs Unstable

Can someone explain the concept of stable and unstable in terms of the Gibbs free energy? Why does a negative free energy mean that its stable?
Wed Feb 13, 2019 12:44 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Heat and Entropy
Replies: 3
Views: 149

Heat and Entropy

Why would you need to use the heat equation before solving for entropy with a temperature change?
Wed Feb 13, 2019 12:39 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Calculating Delta S with a change in temperature
Replies: 5
Views: 220

Calculating Delta S with a change in temperature

If the problem does not specify, do you use C(@constant pressure) or C(@constant volume) when calculating delta S with a temperature change?
Sun Feb 10, 2019 6:25 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs Irreversible
Replies: 9
Views: 315

Re: Reversible vs Irreversible

Irreversible systems have a constant pressure. Reversible systems have a changing external pressure, and we use the integral to add up all the infinitely small work increments from each change in pressure
Sun Feb 10, 2019 6:25 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs Irreversible
Replies: 9
Views: 315

Re: Reversible vs Irreversible

Irreversible systems have a constant pressure. Reversible systems have a changing external pressure, and we use the integral to add up all the infinitely small work increments from each change in pressure
Sun Feb 10, 2019 4:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Ways to find q
Replies: 1
Views: 116

Ways to find q

What are the different ways to find q in a reaction if you don't have a change in temperature to put in the mCdeltaT/nCdeltaT equations?
Sun Feb 10, 2019 4:40 pm
Forum: Phase Changes & Related Calculations
Topic: Work equation
Replies: 4
Views: 193

Re: Work equation

You would multiply the amount of atm*L that you have by 101.325 J/atm*L to get your final answer in Joules.
Wed Feb 06, 2019 11:03 am
Forum: Phase Changes & Related Calculations
Topic: Negative work
Replies: 11
Views: 377

Re: Negative work

Negative work is represented by a system doing work on its surroundings. When work is done on system, it is positive work.
Wed Feb 06, 2019 10:57 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Irreversible/Reversible Processes
Replies: 3
Views: 133

Re: Irreversible/Reversible Processes

Reversible processes do more work because the work is the integral of many consecutive efforts of changing pressure. Irreversible processes has a constant pressure and only has one whole effort.
Sun Feb 03, 2019 2:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Specific Combustion Reaction
Replies: 2
Views: 100

Specific Combustion Reaction

When you are writing a combustion reaction for H2, how do you know not to put CO2 on the product side? I thought all combustion reaction occur in the presence of oxygen and yields carbon dioxide and water?
Mon Jan 28, 2019 12:44 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity
Replies: 8
Views: 245

Re: Heat Capacity

It’s important to note the difference between heat capacity and specific heat capacity. Heat capacity is not dependent on the amount of substance there is, and is an extensive property. Specific heat capacity does depend on the amount of substance there is, and is an intensive property.
Mon Jan 28, 2019 12:41 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Water specific heat capacity
Replies: 2
Views: 91

Water specific heat capacity

Why is the specific heat capacity of water so high?
Mon Jan 28, 2019 12:36 pm
Forum: Phase Changes & Related Calculations
Topic: Standard entalpy of formation
Replies: 6
Views: 209

Standard entalpy of formation

Which molecules have a standard enthalpy formation of 0? And why?
Mon Jan 28, 2019 12:33 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy signs
Replies: 13
Views: 449

Re: Enthalpy signs

Enthalpy is the amount of heat absorbed in a reaction. If the reaction is endothermic, it absorbs heat, so the sign of enthalpy is therefore postitive. It is negative if the reaction is exothermic, and so it is releasing heat, therefore is going to have a negative enthalpy.
Mon Jan 28, 2019 12:30 pm
Forum: Phase Changes & Related Calculations
Topic: State Properites
Replies: 7
Views: 219

Re: State Properites

State properties do not depend on the path taken. For example, for work, it depends on the distance traveled. A system that takes a shorter path will have performed less work than a system that a system that took a longer path. The final value is dependent on how the system was carried out.
Wed Jan 16, 2019 5:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ice table coefficients [ENDORSED]
Replies: 6
Views: 374

Ice table coefficients[ENDORSED]

Is the coefficient of the change row in the ICE table always match the stoichiometric coefficients of the reaction?
Thanks!
Wed Jan 16, 2019 5:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Using a Eq. table for questions
Replies: 1
Views: 58

Using a Eq. table for questions

How do you know which K value to use in an K eq. table when the equation you are looking at is comprised of two smaller equations with two different k values?
Wed Jan 16, 2019 5:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: using ICE when you have a product concentration
Replies: 1
Views: 90

using ICE when you have a product concentration

If the only reactant is a solid, and the problem gives you a concentration for one of the products, can someone explain why for the initial change it is still positive x for both of the products?
Thanks!
Wed Jan 09, 2019 8:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE chart
Replies: 1
Views: 71

ICE chart

Can someone explain what is the purpose of the ICE chart is? And, how to calculate the C portion of it?
Wed Jan 09, 2019 8:31 pm
Forum: Ideal Gases
Topic: Units
Replies: 19
Views: 408

Units

When we are calculating using the ideal gas law, should we put the temperature in Kelvins or in Celsius?
Wed Jan 09, 2019 8:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Concentrations
Replies: 4
Views: 131

Equilibrium Concentrations

Hi!
When we calculate K, are we using equilibrium concentrations or initial concentrations?
Thanks guys!
Thu Dec 06, 2018 10:27 am
Forum: Conjugate Acids & Bases
Topic: Inverse Proportional
Replies: 2
Views: 129

Inverse Proportional

So the strength of the conjugate acid/base is inversely proportional to the strength of the acid/base?
Thu Dec 06, 2018 10:26 am
Forum: Lewis Acids & Bases
Topic: Lewis and Bronsted
Replies: 8
Views: 312

Re: Lewis and Bronsted

Lewis acids/bases are a more general concept than the Bronsted acids/bases. Bronsted acids are proton donors and bronsted bases are proton acceptors. Lewis acids are electron acceptors and Lewis bases are electron donors.
Thu Dec 06, 2018 10:09 am
Forum: Lewis Acids & Bases
Topic: Resonance and acids
Replies: 2
Views: 202

Resonance and acids

If a molecule has resonance, does that mean they are a stronger or weaker acid?
Thu Dec 06, 2018 10:08 am
Forum: Lewis Acids & Bases
Topic: Metal oxides
Replies: 1
Views: 43

Metal oxides

Can someone explain in detail the properties of metal oxides? and which ones are acids and bases?
Thu Dec 06, 2018 10:06 am
Forum: Bronsted Acids & Bases
Topic: Donating H protons
Replies: 2
Views: 159

Donating H protons

So if a molecule contains 2 hydrogen atoms does that mean it can donate 2 H+ and be a strong bronsted acid?
Wed Nov 28, 2018 4:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: ClO2+
Replies: 7
Views: 554

Re: ClO2+

This molecule has a bent shape. There are three electron densities and one lone pair, making the molecular shape bent.
Wed Nov 28, 2018 4:32 pm
Forum: Hybridization
Topic: pi bonds
Replies: 3
Views: 160

Re: pi bonds

Sigma bonds are involved in hybridization, but pi bonds are not involved in hybridization.
Wed Nov 28, 2018 4:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Equatorial axis
Replies: 1
Views: 69

Equatorial axis

Can someone explain more in detail about the equatorial and axial axis?
Wed Nov 28, 2018 4:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Identifying intermolecular forces
Replies: 4
Views: 183

Re: Identifying intermolecular forces

Every interaction between two molecules have London Dispersion Forces. Hydrogen bondings occurs when an H comes into contact with either an F, O, or N atom. Dipole-dipole forces occur that two polar molecules come into contact.
Wed Nov 28, 2018 4:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar and Non-Polar
Replies: 2
Views: 106

Re: Polar and Non-Polar

You have to look at the electronegativities of the atoms. In a bond, one atom's electrons will be pulled towards the atom that has a greater electronegativity, resulting in a net partial charge. Do this for each atom. If all of the attached atoms are the same and their partial charges cancel out, th...
Sun Nov 25, 2018 12:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Naming
Replies: 5
Views: 175

Naming

If a molecule does not have lone pairs in the Lewis structure, then does that mean that both the electron arrangement and the molecular shape are going to be the same?
Sun Nov 25, 2018 12:55 pm
Forum: Hybridization
Topic: Equatorial lone pair
Replies: 2
Views: 96

Equatorial lone pair

Can someone explain in detail the importantance of an equatorial lone pair ?
Sun Nov 25, 2018 12:52 pm
Forum: Hybridization
Topic: Atomic orbitals
Replies: 1
Views: 82

Atomic orbitals

Can someone explain how to find out the number of atomic orbitals in a molecule?
Fri Nov 16, 2018 11:42 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion and Stability
Replies: 3
Views: 60

Re: Repulsion and Stability

If the repulsion is low, that means that the electrons won’t be close to each other to have repulsion. Therefore, the electrons are farthest from each other. The closer the electrons, the more repulsion.
Fri Nov 16, 2018 11:40 am
Forum: Ionic & Covalent Bonds
Topic: Polar/non polar molecules
Replies: 5
Views: 230

Re: Polar/non polar molecules

A main thing to look out for is if the pulls from the electronegative atoms cancels out. If they do, it’s non polar, if they don’t it’s polar. You need to look at the shape and see if there is an uneven distribution of electrons.
Tue Nov 13, 2018 10:22 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Determining the polarizability
Replies: 4
Views: 250

Determining the polarizability

Is charge relevant when looking at which anion is more polarizable? Or do we just look at the size of the atom?
Wed Nov 07, 2018 11:54 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 11
Views: 408

Re: Formal Charge

Formal charge is dependent on the molecule the atom is in! There is no predetermined formal charge for an atom or element, it will vary based on what it is reacting with and whether that molecule is stable or not.
Wed Nov 07, 2018 11:52 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Electron distortion
Replies: 3
Views: 228

Electron distortion

Can someone explain the concept of how bigger atoms have more electron distortion and how that leads to a higher polarization?
Wed Nov 07, 2018 11:49 pm
Forum: Lewis Structures
Topic: Double Bonds
Replies: 7
Views: 284

Re: Double Bonds

You need to check the formal charges of the atoms. The number of electrons drawn might be correct, but it will not be the most stable lewis structure until you make the formal charges as low as possible. A double bond can make the formal charges lower.
Wed Oct 31, 2018 6:14 pm
Forum: Electronegativity
Topic: Periodic Trends [ENDORSED]
Replies: 3
Views: 189

Re: Periodic Trends[ENDORSED]

Electronegativity increases as you go to the right on the periodic table because it is continuously getting more stable when you add more valence electrons to the outermost shell, and therefore the atom will have a higher tendency to want to keep those electrons. Therefore, the more the atom wants t...
Wed Oct 31, 2018 6:12 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 8
Views: 389

Re: Resonance

The bond length allows to have more insight on how strong the bond is as well!
Wed Oct 31, 2018 6:11 pm
Forum: Trends in The Periodic Table
Replies: 2
Views: 165

Use the periodic trends of atomic radii, and why this is what it is, to formulate your answer. As we go towards the right of the periodic table, the effective nuclear charge increases, and therefore, has a stronger pull on the electrons, making the radius of the atom smaller. As we go down the perio...
Tue Oct 23, 2018 5:30 pm
Forum: Properties of Electrons
Topic: Difference between electron's particle like and wave like characteristics
Replies: 5
Views: 260

Re: Difference between electron's particle like and wave like characteristics

The photoelectric effect demonstrates how electrons and light (little packets of energy called photons) have particle like properties. Their interaction is based on a one electron one photon interaction. According to De Broglie, anything that has rest mass has wave like properties, they can diffract...
Tue Oct 23, 2018 1:08 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect original purpose
Replies: 2
Views: 191

Re: Photoelectric Effect original purpose

Another purpose of the photoelectric effect is that it demonstrates how electrons and light have particle like properties, since there is a one electron one photon interaction in this experiment.
Mon Oct 22, 2018 10:07 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: When to double the parameter to get delta v
Replies: 3
Views: 347

When to double the parameter to get delta v

In the homework, there are questions that asked for the minimum uncertainty of the object's position, and when it said minimum, the solution's manual did not double the parameter of the velocity. Although, when it does not say minimum, they double the parameter? Does the word "minimum" pla...
Wed Oct 17, 2018 6:56 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes
Replies: 3
Views: 104

Re: Nodal Planes

In a nodal plane, there is 0 probability of finding an electron, therefore the electron density goes to 0 approaching a nodal plane.
Wed Oct 17, 2018 6:51 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg equation
Replies: 4
Views: 218

Rydberg equation

Can someone explain what the rydberg equation tells us conceptually?
Wed Oct 17, 2018 4:53 pm
Forum: Properties of Light
Topic: energy equation
Replies: 4
Views: 140

energy equation

How do I know when to use just the equation E=hv or when to use E=(hc)/v to find the energy of a photon?
Tue Oct 09, 2018 5:12 pm
Forum: Molarity, Solutions, Dilutions
Topic: Finding the volume of stock solution to dilute
Replies: 13
Views: 745

Re: Finding the volume of stock solution to dilute

I would suggest always converting to Liters because molarity is moles/liters and the units always have to be consistent!
Tue Oct 09, 2018 5:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 2 Homework
Replies: 4
Views: 168

Re: Week 2 Homework

The homework is due in the discussion sessions every week.
Tue Oct 09, 2018 5:08 pm
Forum: SI Units, Unit Conversions
Topic: Formula Units
Replies: 2
Views: 112

Re: Formula Units

It is the same method as finding the amount of atoms in an element, you use avogrado's constant. Formula units are applied to molecules and compounds!
Tue Oct 09, 2018 5:07 pm
Forum: Significant Figures
Topic: Sig Fig zero rules
Replies: 7
Views: 777

Re: Sig Fig zero rules

Pay attention to decimal points! Those indicate whether you count the zeros as significant figures in some cases.
For example 5000 has one significant figure, but 5000. has 4 significant figures!

I hope this helps!
Wed Oct 03, 2018 11:23 am
Forum: Molarity, Solutions, Dilutions
Topic: Concentration Calculations
Replies: 8
Views: 2824

Re: Concentration Calculations

How do we know when not to use the formula M(initial)V(initial) = M(final)V(Final)? That was my plan for this problem, but it does not work out.
Mon Oct 01, 2018 3:46 pm
Forum: SI Units, Unit Conversions
Topic: Naming Compounds
Replies: 8
Views: 337

Naming Compounds

Is there a trick in knowing how to write out Calcium sulfide in molecular terms?
Mon Oct 01, 2018 3:18 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Calculating the amount of atoms in a sample
Replies: 2
Views: 99

Calculating the amount of atoms in a sample

How do you find the amount of formula units for a compound that are present in a given sample (in grams)?