Search found 39 matches
- Sun Mar 17, 2019 6:06 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Spontaneous reactions
- Replies: 11
- Views: 4545
Re: Spontaneous reactions
Gibbs free energy determines spontaneity, not enthalpy alone. However it does play a role. Using the equation ΔG= ΔH- TΔS and making a chart for positive and negative values of ΔS and ΔH should help you better determine what conditions are necessary for spontaneity of the forward reaction.
- Sun Mar 17, 2019 6:03 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: standard cell potential and free energy
- Replies: 3
- Views: 507
Re: standard cell potential and free energy
While cell potential is an intensive property, gibbs free energy is an extensive property as it is dependent on the moles of electrons transferred.
- Sun Mar 17, 2019 6:01 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Platinum Electrode
- Replies: 3
- Views: 501
Re: Platinum Electrode
If there is no conducting electrode in one of the two half reactions then you would use it as the anode/cathode.
- Sun Mar 17, 2019 5:58 pm
- Forum: Biological Examples (*DNA Structural Transitions, etc.)
- Topic: Hemoglobin and Equilibrium
- Replies: 4
- Views: 2799
Re: Hemoglobin and Equilibrium
What would be the catalyst/enzyme included in this reaction?
- Sun Mar 17, 2019 5:57 pm
- Forum: Biological Examples (*DNA Structural Transitions, etc.)
- Topic: DNA Structural Transition
- Replies: 4
- Views: 1484
Re: DNA Structural Transition
This is the mechanism by which the body begins the process of transcription/translation and is relevant in terms of its endergonic nature.
- Sun Mar 17, 2019 5:55 pm
- Forum: Biological Examples (*DNA Structural Transitions, etc.)
- Topic: Structures of the Human Body and Systems
- Replies: 5
- Views: 1327
Re: Structures of the Human Body and Systems
The human body is an indeed an open system as the heat produced by our body is given off continuously, as we take in resources.
- Sun Mar 17, 2019 5:54 pm
- Forum: Van't Hoff Equation
- Topic: Test #2
- Replies: 5
- Views: 727
Re: Test #2
The key here is to use the Van't Hoff Equation to find K2 at the temperature 30 celsius. I got 1.471^-14. Then take the square root of Kw to solve for your hydronium concentration and take the -log of the value. This will result in your new neutral pH. Comparing to see wether 7 is larger (meaning ba...
- Sun Mar 17, 2019 5:48 pm
- Forum: Van't Hoff Equation
- Topic: Temp Units
- Replies: 11
- Views: 1312
Re: Temp Units
^Kelvin would be the units used, however if you get confused just remember that the gas constant R in the Van't Hoff Eq has units of J/K *mol.
- Sun Mar 17, 2019 5:46 pm
- Forum: Van't Hoff Equation
- Topic: neutral pH not 7?
- Replies: 6
- Views: 997
Re: neutral pH not 7?
Kw is temperature dependent and therefore the concentration of [h30+] and [oh-], calculated by the square root of Kw, will be different.
- Sun Mar 17, 2019 5:45 pm
- Forum: Van't Hoff Equation
- Topic: Constants
- Replies: 3
- Views: 634
Re: Constants
As the Van't Hoff Equation is used when the temperature is different for a given reaction, the change in enthalpy and entropy for the reaction remains the same as they are independent of temp and therefore t is the only variable that is different in two situations (where t1 is raised or lowered to t...
- Sun Mar 17, 2019 5:42 pm
- Forum: Van't Hoff Equation
- Topic: pH and van’t hoff
- Replies: 6
- Views: 1392
Re: pH and van’t hoff
A neutral pH of 7 is only true for water at 25 degrees celsius. As the temperature changes, Kw changes and therefore as [h30+] is calculated by taking the square root of Kw, the neutral pH value will differ accordingly.
- Sun Mar 17, 2019 5:40 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: U=0
- Replies: 6
- Views: 3163
Re: U=0
Yes, for ideal gases; reversible expansion the total change in internal energy should be 0 while q and w are the ones that vary depending on the situation.
- Sun Mar 17, 2019 5:37 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: DeltaU = 3/2 nRT
- Replies: 3
- Views: 890
Re: DeltaU = 3/2 nRT
This correct for monoatomic molecules while the diatomic molecule formula U=5/2 nRT
- Sun Mar 17, 2019 5:35 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Q6 on the midterm
- Replies: 3
- Views: 547
Re: Q6 on the midterm
Being that the total number of moles of gas increased, the reaction is doing work.
- Sun Mar 17, 2019 5:33 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Heat and Entropy
- Replies: 2
- Views: 401
Re: Heat and Entropy
If we are considering Entropy for a phase change or heating up a substance, the same should apply assuming the same conditions.
- Sun Mar 17, 2019 5:31 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: free expansion
- Replies: 2
- Views: 498
Re: free expansion
For free expansion there is no acting external pressure as it is in a vacuum and therefore no work being done. The insulation accounts for a lack of transfer of heat.
- Sun Mar 17, 2019 5:30 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: w=-PdeltaW
- Replies: 5
- Views: 700
Re: w=-PdeltaW
When the system is under constant pressure, this equation gives you the work done by the expansion or compression of the gases. Think of a piston changing the volume of enclosed gases, as it can be derived using PV=nRT so change in moles of gas*n*R*T can also be used accordingly.
- Sun Mar 17, 2019 5:27 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Midterm Question 6
- Replies: 6
- Views: 928
Re: Midterm Question 6
I used delta n*r*t to solve for work with a change of moles of 6. Which resulted in 28.58 Kj of work. Subtracted from n*enthalpy= -11512 gave me -11540 Kj
- Sun Mar 17, 2019 5:20 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes
- Replies: 11
- Views: 1344
Re: Phase Changes
Yes, as well as understand how to incorporate the enthalpy of heating a substance as well as 3 step problems have been covered a lot.
- Sun Mar 17, 2019 5:18 pm
- Forum: Phase Changes & Related Calculations
- Topic: Isothermic vs. Adiabatic
- Replies: 3
- Views: 627
Re: Isothermic vs. Adiabatic
They pertain to solving for change in U, as in Isothermic conditions there is no change in temp. but work is done equivalent to -q which is the change in U. For adiabatic conditions there is no heat transferred. Basically under both conditions keep in mind that q=0.
- Sun Mar 17, 2019 5:13 pm
- Forum: Phase Changes & Related Calculations
- Topic: rotational v vibrational energy
- Replies: 5
- Views: 850
Re: rotational v vibrational energy
Vibrational energy is the energy that arises from atoms moving along a axis (ie: within a bond). Rotational energy is the energy that arises from a molecule rotating around an axis (can be thought of as a molecules ability to rotate about its position)
- Sun Mar 17, 2019 5:07 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Partial Pressure
- Replies: 4
- Views: 626
Re: Partial Pressure
Pure solids and liquids should be excluded from the partial pressure equilibrium constant calculations.
- Sun Mar 17, 2019 5:03 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Midterm Q3-C
- Replies: 4
- Views: 656
Re: Midterm Q3-C
Given that pKa=10 , and that it is a weak acid, an amount x is ionized so there is an x amount of hydronium. However being that HA is a weak acid the amount ionized is very small compared to [HA] therefore it cannot equal [H30+].
- Sun Mar 17, 2019 4:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Effect of increased concentration on equilibrium
- Replies: 9
- Views: 1430
Re: Effect of increased concentration on equilibrium
The reaction would compensate by forming more products and therefore shift to the right.
- Sun Mar 17, 2019 4:57 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Equation
- Replies: 9
- Views: 1250
Re: Equation
Correct, if we assume A=1, it should cancel out in the derivation for this condition.
- Sun Mar 17, 2019 4:54 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Plot of Arrhenius function
- Replies: 4
- Views: 767
Re: Plot of Arrhenius function
Using the information of given in Arrhenius function should we be able to get the plot of the rate law?
- Sun Mar 17, 2019 4:52 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pKa vs. pH
- Replies: 15
- Views: 2944
Re: pKa vs. pH
pH can be solved for by taking the -log of the concentration of hydronium ions, and therefore quantitatively describes the acidity or basicity of a solution. pKa is found taking the -log of the ionization constant of an acid, and can therefore be used to understand the strength of an acid.
- Sun Mar 17, 2019 4:49 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature and Le Chatlier's Principle
- Replies: 6
- Views: 823
Re: Temperature and Le Chatlier's Principle
If a reaction is exothermic, a rise in temperature will shift the system in favor of the products (i.e: to the left), if it is exothermic the system will shift in favor of the reactants (i.e: the right). This is due to the fact that higher temperatures will favor the direction with higher energy.
- Sun Mar 17, 2019 4:45 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Effects of Compression
- Replies: 5
- Views: 585
Re: Effects of Compression
Yes, using Le Chatelier's principles this can be concluded as compression would result in a shift to the side of the reaction with less moles whereas expansion would shift to the side with a larger amount of moles.
- Sun Mar 17, 2019 4:41 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding an Inert Gas
- Replies: 4
- Views: 570
Re: Adding an Inert Gas
Adding an Inert gas does not actually cause the system to shift to either side as it does not take part in the chemical reaction.
- Sun Nov 04, 2018 11:59 pm
- Forum: Trends in The Periodic Table
- Topic: Ranking of effects on Periodic trends
- Replies: 1
- Views: 212
Re: Ranking of effects on Periodic trends
I had the same question of overlapping trends, however I think if you take into account the strength of say the effective nuclear charge, as compared with the removal or addition of electrons it reveals itself.
- Sun Nov 04, 2018 11:56 pm
- Forum: Lewis Structures
- Topic: Steps for Lewis Structures
- Replies: 3
- Views: 322
Re: Steps for Lewis Structures
Is it necessary to write formal charges at all times? Or only when explicitly told to do so? Also, for resonance structures is a hybrid resonance structure always expected if there are in fact delocalized double or triple bonds?
- Sun Nov 04, 2018 11:52 pm
- Forum: Ionic & Covalent Bonds
- Topic: electronegativity difference
- Replies: 4
- Views: 553
Re: electronegativity difference
If the difference in electronegativity of a molecule falls between 2 and 1.5 would it be necessary to classify said bond as a covalent bond with ionic characteristics or would it simply be a covalent bond?
- Sun Oct 14, 2018 11:29 pm
- Forum: DeBroglie Equation
- Topic: detectability of waves
- Replies: 4
- Views: 411
Re: detectability of waves
I had understood it was at x10^-12 m as that was the wavelength of an electron in an atom, however I'm not entirely certain
- Sun Oct 14, 2018 11:26 pm
- Forum: Properties of Electrons
- Topic: 7th Edition HW 1E.9
- Replies: 2
- Views: 216
Re: 7th Edition HW 1E.9
I started by converting the units of mass of the baseball from ounces to grams, and then substituting the given values into the De Broglie equation.
- Fri Oct 12, 2018 12:39 am
- Forum: Significant Figures
- Topic: significant figures
- Replies: 5
- Views: 665
Re: significant figures
Lets say I'm multiplying a value like (225.099) times a constant such as the speed of light (3.00x10^8). Do I simply use three significant figures because of the constant?
- Fri Oct 05, 2018 9:47 am
- Forum: SI Units, Unit Conversions
- Topic: formula units [ENDORSED]
- Replies: 69
- Views: 32380
Re: formula units [ENDORSED]
The "formula units" phrasing throws me off a bit for a question where I am trying to find the "formula units of compound" in a certain amount of grams. Do I just set it up as conversion from grams to moles using molecular weight and solve for the moles of the compound as a whole?
- Fri Oct 05, 2018 9:40 am
- Forum: Significant Figures
- Topic: Scientific Notation
- Replies: 7
- Views: 379
Re: Scientific Notation
I had the same problem of not knowing when scientific notation is actually required. More specifically if its neccesary to do all our work in this form or can I use decimals up until reaching the final solution?
- Fri Oct 05, 2018 9:12 am
- Forum: General Science Questions
- Topic: Common ions
- Replies: 4
- Views: 545
Re: Common ions
Something that really helps me is having a piece of paper on which I have all the info regarding common ions, (name, symbols/formulas) to reference while studying and doing homework. Over time you'll become more familiarized the more you use them, but it helps to have that as a reiteration.