delta G is more positive when the partial pressure of the product/s increases.
delta G is more negative when the partial pressure of the reactant/s increases.
Search found 27 matches
- Mon Mar 16, 2020 5:51 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: factors of Gibbs free energy
- Replies: 2
- Views: 276
- Mon Mar 16, 2020 5:43 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst K vs Q
- Replies: 14
- Views: 1032
Re: Nernst K vs Q
If you use K, that means you are using the ratio of products to reactants at equilibrium. This would give you E of 0, as a battery or cell is essentially dead at equilibrium. Voltage is generated by electron flow, and electrons flow until the system reaches equilibrium. Thus once equilibrium has be...
- Mon Mar 16, 2020 5:33 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Finding the concentration of cathodes/ anodes
- Replies: 2
- Views: 365
Re: Finding the concentration of cathodes/ anodes
Yes, you can use the Nernst equation, provided all the other info is given. If it's a concentration cell, the cathode is the half-cell with the higher concentration, so it'll be the reactant. If it's a normal galvanic cell, you would identify the reactant and product from the overall equation of th...
- Mon Mar 16, 2020 5:26 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: calculating standard cell potential
- Replies: 6
- Views: 570
Re: calculating standard cell potential
You have to determine which of the half rxns is the cathode (reduction) and anode (oxidation). Then you plug in the given E values for those reactions to the formula Ecell = Ecat - Ean.
- Mon Mar 16, 2020 5:18 pm
- Forum: General Rate Laws
- Topic: Rate Constants
- Replies: 3
- Views: 387
Re: Rate Constants
To be pseudo-first-order, the concentration of one of the reactants in the rate law must be increased to be much larger than the concentration of the other reactant. For example, look at #15 from ENDGAME. The concentration of A has been increased so much that even when A is used up by the reaction,...
- Mon Mar 16, 2020 5:01 pm
- Forum: First Order Reactions
- Topic: size
- Replies: 6
- Views: 528
Re: size
I read that if a particle (ie. solid reactant) is broken down into small bits, it leads to greater surface area and a faster reaction rate. But it doesn't affect the formed products in any way.
- Sun Mar 01, 2020 11:55 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Importance of pH?
- Replies: 2
- Views: 223
Re: Importance of pH?
Deepika Reddy 1A wrote:I believe that it is important because it determines how you balance the redox half-reactions. Depending on whether the solution is acidic or basic, the solution is balanced differently.
Can you pls tell me the different approach on balancing a rxn based on acidity/basicity?
- Sun Mar 01, 2020 11:48 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Voltage vs Gibbs
- Replies: 2
- Views: 234
Re: Voltage vs Gibbs
A negative Gibbs free energy means a spontaneous reaction. From the eq deltaG= -nFE, a positive E will still result to a negative value. If it's a negative E, then deltaG would be positive since the negative sign in front of n will be cancelled out and turn to a positive sign. That in turn will be a...
- Sun Mar 01, 2020 11:37 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Free energy
- Replies: 3
- Views: 362
Re: Free energy
If Ecell > 0, then the deltaG is more negative. That shows a spontaneous reaction.
- Sun Mar 01, 2020 11:33 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n value
- Replies: 9
- Views: 609
Re: n value
It's the number of electrons transferred from the balanced half reactions (reduction and oxidation).
- Sun Mar 01, 2020 11:30 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Reduced/Oxidized based on Ecell
- Replies: 6
- Views: 472
Reduced/Oxidized based on Ecell
I learned that the more positive Ecell refers to the reaction being reduced. If the given Ecell for two reactions have the same value, which will be considered oxidized/reduced?
- Mon Feb 17, 2020 12:13 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: entropy based on molecular name/structure
- Replies: 2
- Views: 312
entropy based on molecular name/structure
Are we supposed to know the structure of molecules according to their names to figure out their respective standard molar entropy? 4H.5 was discussed by my TA.
- Sun Feb 16, 2020 11:49 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Temperature Dependence
- Replies: 4
- Views: 411
Re: Van't Hoff Temperature Dependence
He mentioned in lecture that you apply this equation to calculate K at different temperatures if deltaH is given.
He broke down the equation to the ln(K2/K1) = -deltaH/R (1/T2 - 1/T1) with the assumption that deltaH is constant.
He broke down the equation to the ln(K2/K1) = -deltaH/R (1/T2 - 1/T1) with the assumption that deltaH is constant.
- Sun Feb 16, 2020 11:41 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: thermodynamically stable
- Replies: 6
- Views: 458
Re: thermodynamically stable
If deltaGf < 0, the reaction is said to be favorable and thermodynamically stable.
- Sun Feb 16, 2020 11:35 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: importance of -RTlnk
- Replies: 7
- Views: 484
Re: importance of -RTlnk
I believe it's simply showing the relation of K to free energy in a way that K replaces Q to show no work has been done for a reaction at equilibrium.
- Wed Feb 05, 2020 7:06 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature
- Replies: 6
- Views: 400
Re: Temperature
It's endothermic reaction since the ice cube needs to absorb heat for the melting process to occur. So is an ice cube melting an example of an exothermic or endothermic reaction? Because the temperature of the water final is greater than the initial temperature and the difference would therefore be ...
- Wed Feb 05, 2020 6:40 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: higher entropies
- Replies: 6
- Views: 828
Re: higher entropies
Entropy is a measure of disorder/randomness. A high entropy shows an increase in disorder (low energy), which is determined by the number of microstates of the given state of matter.
- Wed Feb 05, 2020 6:24 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: C = K?
- Replies: 5
- Views: 394
Re: C = K?
It's the idea of raising the temp. by 1 degree C or K. You can use those scales interchangeably if the problem concerns delta T. Otherwise, a regular T in question would have different measured values for each scale.
- Wed Feb 05, 2020 6:17 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: 6C.13
- Replies: 3
- Views: 173
Re: 6C.13
You rank increasing basicity by increasing pKa. I follow this pattern for figuring out this type of problem. Hope it helps!
Strong acids: High Ka, Low pKa (High pKb)
Strong bases: High Kb, Low pKb (High pKa)
Strong acids: High Ka, Low pKa (High pKb)
Strong bases: High Kb, Low pKb (High pKa)
- Wed Feb 05, 2020 6:12 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: approximation
- Replies: 4
- Views: 211
Re: approximation
Approximation of x is done if K < 10^-3. That means you can take out the x in the denominator (reactants) because it won't have a significant effect on the value you'll obtain at the end. If unsure, you can confirm the approximation when x < 5% of the initial concentration of the molecule asked to b...
- Mon Jan 20, 2020 1:01 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding Inert Gas
- Replies: 9
- Views: 594
Re: Adding Inert Gas
Diana A 2L wrote:What is considered an inert gas? Do we have to remember a list of them or is there a way to tell if a gas is inert?
My TA said that inert gas is another term for noble gases. The common ones we might see in reactions are He and Ar.
- Mon Jan 20, 2020 12:53 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Combining Reactions
- Replies: 3
- Views: 165
Re: Combining Reactions
Determining the K for the third reaction depends on the layout of its reactants/products. You might need to write the first or second reaction in reverse direction where the K becomes its inverse (1/K). But ultimately, K3=K1 x K2.
- Sun Jan 12, 2020 9:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K
- Replies: 10
- Views: 417
Re: K
Kc and Kp are both measures of equilibrium constants of a reaction based on the molar concentration and partial pressure of molecules respectively. Although they follow the same ratio of P/R, be mindful that Kc uses [] and Kp uses () while both have their coefficients in the reaction represented as ...
- Sun Jan 12, 2020 9:09 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Calculating Q
- Replies: 16
- Views: 804
Re: Calculating Q
Q is calculated the same way as K = [P]/[R], including only the aqueous/gas molecules. Though Q is determined for reactions that are not in equilibrium state.
- Sun Jan 12, 2020 9:06 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 5
- Views: 248
Re: Le Chatelier's Principle
It's a principle that explains how a reaction adjusts and minimizes the effect of change brought by circumstances that disrupts its equilibrium state. The affecting conditions can be change in molar concentration, pressure or temperature. For instance, an increase in the molar concentration of produ...
- Sun Jan 12, 2020 8:52 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5.61
- Replies: 3
- Views: 174
Re: 5.61
The molar concentration of aqueous and gas molecules is the primary significant factor that can change the direction of an equilibrium reaction. It does not deal with pure solids and liquids, thus increasing water concentration will not shift the reaction nor influence its K value.
- Sun Jan 12, 2020 8:42 pm
- Forum: Ideal Gases
- Topic: ICE tables
- Replies: 4
- Views: 327
Re: ICE tables
ICE table aims to determine the molar concentration of a species in various set points of a reaction. Each letter represents the following: initial, change and equilibrium molar concentration. It's the best approach to calculate K of the given reaction, or figure out the composition of an equilibriu...