## Search found 52 matches

Wed Mar 21, 2018 7:01 am
Forum: General Rate Laws
Topic: rate proportions
Replies: 2
Views: 461

### Re: rate proportions

If a reaction is first order then the rate will be doubled when the reactant is doubled. If the reaction is second order and only has one reactant, then doubling the reactant will cause the rate to be squared.
Wed Mar 21, 2018 6:59 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: k1 and k2
Replies: 2
Views: 1615

### Re: k1 and k2

K of reaction step 2 can equal k2/k'2. The equilibrium applies to all equations and is a ratio of forward rate reaction constant to reverse rate reaction constant.
Wed Mar 21, 2018 6:57 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius equation
Replies: 2
Views: 441

### Re: Arrhenius equation

No, just make sure to match T1 with k1 and T2 with k2
Sun Mar 11, 2018 11:25 pm
Forum: General Rate Laws
Topic: Units
Replies: 11
Views: 835

### Re: Units

While these are common units for these types of problems, it does not have to be these units specifically. Use whatever is consistent with the problem.
Sun Mar 11, 2018 11:24 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Finding n
Replies: 4
Views: 408

### Re: Finding n

My TA mentioned that for problems in this class, n will always be close to a whole number.
Sun Mar 11, 2018 11:22 pm
Forum: Second Order Reactions
Topic: the slope
Replies: 12
Views: 827

### Re: the slope

negative k for zero and first order reaction rates and positive k for second order reaction rates
Sun Mar 04, 2018 9:46 pm
Forum: General Rate Laws
Topic: Stoichiometry coefficients
Replies: 3
Views: 248

### Re: Stoichiometry coefficients

No the rate law is determined from experimental data.
Sun Mar 04, 2018 9:45 pm
Forum: Zero Order Reactions
Topic: K limiting rate
Replies: 3
Views: 251

### Re: K limiting rate

Each reaction has a unique rate. A higher k means a faster reaction and a lower k means a slower reaction. When you multiply k times the concentrations in the rate law, you get the unique reaction rate for the specific reaction.
Sun Mar 04, 2018 9:41 pm
Forum: First Order Reactions
Topic: k
Replies: 16
Views: 843

### Re: k

Most problems keep k in terms of seconds however it is ok to convert to other units if needed for the problem.
Sun Feb 25, 2018 11:51 pm
Forum: General Rate Laws
Topic: Rate of Reaction
Replies: 4
Views: 284

### Re: Rate of Reaction

Since the stoichiometric coefficients are 2 for NO2 and 1 for O2, the rate of O2 production will be half of that of NO2 depletion.
Sun Feb 25, 2018 11:47 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: activation energy
Replies: 4
Views: 263

### Re: activation energy

A higher activation energy means there is a higher energy barrier for the reaction. This means more energy is needed for the reaction to proceed which will require a longer amount of time in most cases.
Sun Feb 25, 2018 11:45 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Tangent line
Replies: 4
Views: 320

### Re: Tangent line

Yes the reaction rate will change as the reaction proceeds. We will always take the instantaneous rate closest to t=0 since this is the maximum rate.
Mon Feb 19, 2018 10:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cells vs Electrochemical Cells
Replies: 4
Views: 423

### Re: Galvanic Cells vs Electrochemical Cells

Electrochemical cells generate electrical energy from chemical reactions. Galvanic cells are a type of electrochemical cell that generate electricity through redox reactions.
Mon Feb 19, 2018 9:50 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Numbers
Replies: 6
Views: 465

### Re: Oxidation Numbers

Oxidation number of an atom in a neutral compound is zero when the substance contains only one element. So O2 and O3 would have an overall charge of zero.
Mon Feb 19, 2018 9:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: anode?
Replies: 5
Views: 373

### Re: anode?

The anode is where oxidation occurs. In this case the Zinc is being oxidized. The Zinc is also referred to as the reducing agent since it is being oxidized
Thu Feb 08, 2018 9:37 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Intensive Property of Standard Cell Potential
Replies: 3
Views: 262

### Re: Intensive Property of Standard Cell Potential

Specific heat capacity is an extensive value and depends on the amount of substance present. Standard cell potential is an intensive value and does not depend on the amount of substance present.
Thu Feb 08, 2018 9:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 7
Views: 412

### Re: Salt Bridge

Even if the diagram does not show a salt bridge, I think it is safe to assume that there is a salt bridge in all redox reactions. If there were no salt bridge there would be a buildup of elections in the cathode and after a certain point, electron flow would stop because of the charge buildup. By ha...
Thu Feb 08, 2018 9:31 pm
Forum: Balancing Redox Reactions
Topic: Standard Reduction Potentials Concept
Replies: 4
Views: 448

### Re: Standard Reduction Potentials Concept

Yes, when you flip a reduction equation, you are basically running the reverse reaction, which is oxidation. You will also need to take the negative of the standard reduction potential.
Sun Feb 04, 2018 9:14 pm
Forum: Phase Changes & Related Calculations
Topic: enthalpy and entropy when it comes to spontaneous reactions
Replies: 6
Views: 405

### Re: enthalpy and entropy when it comes to spontaneous reactions

Spontaneity is determined by multiplying temperature (in kelvin) and enthalpy and subtracting this from entropy. If this value is negative, the reaction is spontaneous.
Sun Feb 04, 2018 9:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: combustion
Replies: 4
Views: 296

### Re: combustion

Yes you can subtract the enthalpies of formation of reactants from the enthalpies of formation of reactants since enthalpy is a state function (path is independent from final and initial state).
Sun Feb 04, 2018 9:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Periodic Trends
Replies: 4
Views: 322

### Re: Periodic Trends

Heat capacity is an extensive property and does not necessarily have trends in the periodic table. It is the amount of heat required to raise 1 mole/gram of substance by 1 degree Celsius/Kelvin. Therefore, it depends on intermolecular forces
Mon Jan 29, 2018 12:56 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy vs. Degeneracy [ENDORSED]
Replies: 5
Views: 358

### Re: Entropy vs. Degeneracy[ENDORSED]

Degeneracy is the amount of states a particles can exist in. Entropy is a measure of disorder in a system. While they both may seem similar, degeneracy is describing the actual number of states and entropy is measured in J/K
Mon Jan 29, 2018 12:52 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy vs. Enthalpy [ENDORSED]
Replies: 2
Views: 162

### Re: Entropy vs. Enthalpy[ENDORSED]

Entropy is calculated by dividing the heat lost/gained in a reversible reaction divided by the temperature of the system. If this reaction occurs at constant pressure then you can substitute q for delta H, or enthalpy change.
Mon Jan 29, 2018 12:49 am
Forum: Phase Changes & Related Calculations
Topic: degeneracy [ENDORSED]
Replies: 7
Views: 424

### Re: degeneracy[ENDORSED]

Degeneracy is the number of ways of achieving a given energy state. An example given in class was that a quarter has a degeneracy of 2 since it can either land on heads or tails. The higher the entropy, the higher amount of possible energy states.
Sun Jan 21, 2018 11:36 pm
Forum: Phase Changes & Related Calculations
Topic: Heating Curve Calculation Confusion
Replies: 3
Views: 229

### Re: Heating Curve Calculation Confusion

This depends on the initial and final temperatures of the system. If the system goes from -10 degrees Celsius to 50 degrees Celsius, you need to calculate
mCdeltaT for -10 degrees to 0 degrees + phase change from ice to liquid + mCdeltaT for 0 degrees to 50 degrees
Sun Jan 21, 2018 11:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond enthalpies
Replies: 4
Views: 318

### Re: Bond enthalpies

We will be given bond enthalpies and we will have to determine reaction enthalpy depending on which bonds are broken and which bonds are formed.
Sun Jan 21, 2018 11:29 pm
Forum: Phase Changes & Related Calculations
Topic: ΔU vs. ΔH
Replies: 10
Views: 1292

### Re: ΔU vs. ΔH

Delta U is a summation of the work done in the system and the heat in the system. In other words, it is a measure of the internal energy of the system. When pressure is constant, there is no work being done. Therefore delta U is equal to delta H under these circumstances.
Sun Jan 14, 2018 9:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpy Definition
Replies: 7
Views: 332

### Re: Standard Reaction Enthalpy Definition

No it does not have to be at this temperature but most reactions happens at 25 degrees Celsius
Sun Jan 14, 2018 7:35 pm
Forum: Phase Changes & Related Calculations
Topic: Methods of Enthalpy
Replies: 8
Views: 473

### Re: Methods of Enthalpy

Yes we learned three methods. The first one involves Hess's Law, the second one uses bond enthalpies, and the third one uses standard enthalpies of formation. The method you use depends on the information given.
Sun Jan 14, 2018 7:28 pm
Forum: Phase Changes & Related Calculations
Topic: Constant temperature
Replies: 3
Views: 172

### Re: Constant temperature

Temperature stays constant during a phase change because the heat is being used to break/make bonds between the molecules.
Sat Dec 09, 2017 8:45 pm
Forum: Bronsted Acids & Bases
Topic: Strong vs. Weak
Replies: 5
Views: 322

### Re: Strong vs. Weak

Strong acids will have more electronegative/electron withdrawing atoms in their formulas. This will allow the proton to break away more easily and for the resulting anion to be stable.
Fri Dec 08, 2017 10:15 am
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: CH3COOH
Replies: 3
Views: 790

### Re: CH3COOH

Acetic acid only loses the hydrogen that is attached to the oxygen because of oxygen's electronegativity. The nonpolar bond between carbon and hydrogen prevents the hydrogens from being donated since electrons are equally shared.
Fri Dec 08, 2017 10:13 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ka and Concentration
Replies: 3
Views: 426

### Re: Ka and Concentration

Ka is the acidity constant, or the equilibrium constant of an acid dissociation equation. It is a ratio of the products concentration to the reactants concentration. On the other hand, [H3O+] is the concentration of hydronium ions and is measured by pH.
Fri Dec 08, 2017 10:10 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Electron Withdrawing Power
Replies: 3
Views: 283

### Re: Electron Withdrawing Power

In respect to oxacids, acids with a greater amount of oxygen will be stronger because the electrons of the resulting anion are more delocalized. This is due to the high electronegativity of oxygen.
Fri Dec 08, 2017 10:08 am
Forum: Bronsted Acids & Bases
Topic: % dissociation
Replies: 3
Views: 367

### Re: % dissociation

You can calculate %dissociation of an acid by dividing the conjugate base concentration by the initial acid concentration. This is a measurement of how much the acid dissociates.
Fri Dec 08, 2017 2:49 am
Forum: Amphoteric Compounds
Topic: Determining Amphoteric Compounds
Replies: 3
Views: 472

### Determining Amphoteric Compounds

How do you determine whether is amphoteric by looking at its formula? Are all compounds with metalloids considered amphoteric?
Fri Dec 08, 2017 2:46 am
Forum: Naming
Topic: Finding Coordination Number
Replies: 6
Views: 485

### Re: Finding Coordination Number

Coordination Number is simply the number of ligands attached to the transition metal. The transition metals contain s,p, and d orbitals and can therefore accommodate many ligands.
Fri Dec 08, 2017 2:44 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Equilibrium Composition
Replies: 4
Views: 432

### Re: Equilibrium Composition

When calculating the concentrations of products/reactants, we can approximate if the equilibrium constant is very small (<10^-5). This does not x is zero, but that x is very small and has a negligible effect.
Thu Dec 07, 2017 2:02 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Difference between pH and pKa?
Replies: 4
Views: 509

### Re: Difference between pH and pKa?

pKa and pH are different. Ka is the equilibrium constant for a reaction that involves an acid. pKa = -log(Ka). pH is a measure of how strong the acid is (how much it disassociates. pH = -log[H+]
Thu Dec 07, 2017 1:58 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.29C
Replies: 1
Views: 207

### Re: 12.29C

Since Ba(OH)2 is a strong base, we know it completely disassociates. For every one mole of Ba(OH)2 that is diasassociated, there will be one mole of Ba+ and two moles of OH-. Therefore we multiply the base's concentration by two to get the concentration of OH-. From here we can calculate pOH
Thu Dec 07, 2017 1:53 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Reason for not including water
Replies: 6
Views: 435

### Re: Reason for not including water

Since water is the solvent, it's concentration will barely be affected. Therefore it is not included in the equilibrium ratio.
Sun Nov 05, 2017 10:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Ionization Energy / Lewis Dot Structures
Replies: 2
Views: 315

### Re: Ionization Energy / Lewis Dot Structures

Since the atomic radius decreases across a period, the energy required to remove an electron becomes higher. Therefore, ionization energy increases from left to right across a periodic table. Chlorine is to the right of beryllium and so it has a higher ionization energy.
Sun Nov 05, 2017 10:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Which one do I draw?
Replies: 5
Views: 462

### Re: Which one do I draw?

I think we will mostly be asked to draw lewis structures to figure out the bonds and areas of high electron density. From VSEPR we will probably be asked to identify molecular structure and bond angles.
Sat Oct 28, 2017 5:41 pm
Forum: Hybridization
Topic: Filling electron shells [ENDORSED]
Replies: 3
Views: 378

### Re: Filling electron shells[ENDORSED]

The 4s orbital is filed first because it is lower in energy compared to the 3d orbital. The lowest energy state is always preferred. Another example of this is with the Chromium and copper examples. The electron in the 4s orbital will move to the 3d orbital in order to the evenly fill the orbitals, ...
Fri Oct 27, 2017 3:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Orbital Shape
Replies: 3
Views: 319

### Re: Orbital Shape

We don't need to know the shapes since we will not be asked to draw them, but it helps to be able to visualize them. For example, the p orbitals have nodes, where no electrons will be found (probability density is zero here). The s orbitals do not have any nodes and electron density is more evenly s...
Sat Oct 21, 2017 9:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electron Spin Quantum Number [ENDORSED]
Replies: 12
Views: 3045

### Re: Electron Spin Quantum Number[ENDORSED]

The electron spin number can be either +1/2 or -1/2. This just tell us whether the electron is spinning clockwise or counterclockwise.
Sat Oct 21, 2017 9:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Hund's Rule [ENDORSED]
Replies: 6
Views: 639

### Re: Hund's Rule[ENDORSED]

Hund's Rule states that due to electron repulsion, electrons in the same subshell occupy different orbitals with parallel spin. This allows for the lowest possible energy state. There are no more than two electrons per orbital. If 2 electrons are in the same orbital they are spin paired.
Fri Oct 13, 2017 3:40 pm
Forum: Properties of Electrons
Topic: Converting Between keV and Joules
Replies: 3
Views: 1105

### Re: Converting Between keV and Joules

1.6022 x 10^-19 J/eV is a ratio that is used to convert between the two units since most equations use Energy in Joules. Also I think k stands for kilo in this case. Therefore it would be 1.6022 x 10^-16J/ keV
Fri Oct 13, 2017 3:33 pm
Forum: Properties of Light
Topic: Exercise 1.9 Sig Fig
Replies: 3
Views: 290

### Re: Exercise 1.9 Sig Fig

I agree, technically the answer should be 6.0 x 10^-7 so that the the number of sig figs remains two. They wrote it as 600 nm so that we can see the wavelength is part of the visible light spectrum.
Fri Oct 06, 2017 7:10 pm
Forum: Significant Figures
Topic: 3 Sig Figs 1795.507? [ENDORSED]
Replies: 5
Views: 536

### Re: 3 Sig Figs 1795.507?[ENDORSED]

1800. only has 4 sig figs if there is a decimal. Without the decimal, there are only two sig figs. In this case, it would be 1.80 x 10^3 for 3 sig figs.
Fri Oct 06, 2017 7:06 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical Coefficients [ENDORSED]
Replies: 12
Views: 1583

### Re: Empirical Coefficients[ENDORSED]

If the answer is .1 away from a whole number, round accordingly. If it isn't then multiply all mole ratios so they are close enough to whole numbers. For example, if one ratio is 2.25, multiply all the ratios by 4 to get whole numbers.
Fri Oct 06, 2017 6:52 pm
Forum: Limiting Reactant Calculations
Topic: Reactant vs. Reagent [ENDORSED]
Replies: 23
Views: 18996

### Re: Reactant vs. Reagent[ENDORSED]

A reactant is a substance that is consumed in the creation of a product in a chemical reaction. A reagent is used to detect, measure, or produce other substances. In other words, a reagent is a more passive reactant (could be a catalyst?). But for the most part, I believe these words can be used int...

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