Chapter 9 Test Flashcards by Robyn Pate

What does Gibbs Free Energy determine?

If the system has enough energy to undergo a process and thereby determine if a reaction will take place

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Electrolytic Cells

Cells that are thermodynamically unfavorable and have negative voltages

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How do you write a net ionic equation for a dissolution?

Write the main thing as a solid then write it as the two ions as aqueous

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What happens in an electrochemical cell as it runs?

The cathode will gain mass and decrease in concentration of its cation because the anode is creating a solid for the cathode. Then, the anode loses mass and increases in its cation because it is using up its solid.

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What temperatures does a positive H and a positive S occur at?

High Temperatures

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Will the higher or lower K value dissociate more?

The higher K value will dissociate more and also increase entropy

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Solvent

Dissolves other substances

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What temperatures does a negative H and a positive S occur at?

All temperatures

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What does all Gibb’s Free Energy stuff need to be to be determined thermodynamically favorable?

Gibbs- Negative
Enthalpy- Negative
Entropy- Positive

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What processes occur when a solution is formed?

The IMFS between solvent particles are overcome
The IMFs between solute particles are overcome
The IMFs between solvent and solute particles must reform.

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How can we decide if a thermodynamic reaction will occur?

If it is under kinetic control. Also, if there is a high activation energy, unfavorable orientation, or high numbers of particles trying to collide simultaneously

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Provide an explanation for the fact that a reaction DOES NOT occur at room temperature but DOES occur as the temperature is increased.

Check its K value. If it is large that means it has a high activation energy but as the temperature increases more particles have enough energy to overcome the activation energy.

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Use Coulombs law to explain the
difference in the solubility of two
substances

Whichever radius is smaller will have a greater Coulombic attractive force meaning that it will have a lower solubility because it will stick together and not separate.

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Oxidation

When an element loses electrons
Oil- Oxidation is loss

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What temperatures does a negative H and a negative S occur at?

Low Temperatures

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Solute

Gets dissolved

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When writing the overall reaction in 9.8 what do you need to make sure you do?

Make sure the electrons will cancel out

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How do you know enthalpy change from a phase change?

If you are breaking bonds(the system is getting more spread out), it requires energy so the enthalpy change is positive. If you are putting together bonds(the system is getting smaller), it releases energy so the enthalpy change is negative.

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What does a K value smaller than 1 represent?

That reactants are favored at equilibrium

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Entropy

Measure of disorder or randomness in a mixture

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What do you always need to do for this unit?

Check units and make sure everything is converted to the same unit

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Explain why the addition of a catalyst can make a reaction occur that doesn’t normally occur at room
temperature even when ΔG<0.

A catalyst lowers the activation energy making the reaction go faster

Anode

The electrode where oxidation occurs and it attracts anions from the salt bridge and the solution in the beaker.
Anode-oxidation- Anions all start with vowels

How are pressure and volume related?

The higher the pressure, the lower the volume

They are indirectly related

How do you determine the Q value?

You do pressure or concentration of the products over the reactants and if there is a constant in front of it make that constant an exponent. Q is when your system is not at equilibrium yet, so K before K exists

What is the enthalpy sign if heat is a product?

Exothermic(negative)

Which way do electrons flow in an electrochemical cell?

From the anode to the cathode FAT CAT - From Anode To CAThode

What does SNAP represent?

Sodium Nitrates Ammonium Potassium - They are all always soluble

When solving for cell potential and free energy what do you need to make sure you do that is not on the equation sheet?

Divide the answer by 1000

What does a K value greater than 1 represent?

That products are favored at equilibrium and that the reaction is thermodynamically favorable

How do you find delta G for coupled reactions?

First make sure the reactions have an intermediate, if not do whatever you need to do. Then add the G value for both together to get the new G value.

What temperatures does a positive H and a negative S occur at?

No Temperatures

Galvanic/Voltaic Cells

Cells that are thermodynamically favorable and have positive voltages

Reduction

When an element gains electrons or oxidation number is reduced Rig- Reduction is gain

What is the enthalpy sign if heat is a reactant?

Endothermic(positive)

What are ways to get a thermodynamically unfavorable reaction to occur?

- Couple it with another chemical reaction - Lower activation energy

What is the relationship to convert between G and K that is not on the equation sheet?

K= e^-deltaG/ RT R= 8.314

Why does something with greater temperature have greater entropy?

It is because the system with a higher temperature will have particles that have greater average kinetic energies and the energies distributed into the particles is greater

What is standard state?

When there is a little circle in the superscript next to a change in G, H, or S. It means temp is 298 K, pressure is 1 atm, solutions are at 1 M

If a reaction says it occured what does that mean?

That it is thermodynamically favorable

Cathode

The electrode where reduction occurs and it attracts cations from the salt bridge and the solution in the beaker because its cations are being used up and it needs more Cathode-reduction- Cation all start with consonants

If you have a negative G value for a forward reaction, what is the sign for its reverse reaction?

Positive

Electrode

Metal placed in each beaker of a electrochemical cell

What things have more entropy?

- Things that are more spread out and have more disorder - The side of a reaction with more moles of gas - The system with greater temperature - The larger atom(more electrons and is more polarizable)

Based off reduction potential how are we supposed to know which reaction is getting reduced?

The highest reduction potential is the reduction reaction and the other one will be the oxidation reaction and it will be flipped(the equation and the voltage)

How do you answer, "What is this reaction driven by..(enthalpy or entropy or both)?"

Whichever one is thermodynamically favorable that is what it is driven by

Purpose of salt bridge

To separate the solutions using cations and anions and the ions in the salt bridge are there to neutralize the charge. Without the salt bridge the reaction wouldn't occur

What does spontaneous mean?

It is thermodynamically favorable. It was random and not forced to happen, however it can go at any pace.

What is more favorable in solution formation and why? - Weak or Strong solvent IMFs - Weak or Strong solute IMFS

Weak for both because you want them to separate easily and create a solution

Review Gibbs Free Energy AP quiz #1

What is a way to separate a solid from the other products?

If that is the only solid you could evaporate the water or whatever else is surrounding it and if there are gases in the products those will evaporate anyways

At 25 degrees the equilbrium constant for the reaction has a value of 1.3. At 50 degrees, the equilibrium constant is less than 1.3. Based on this information what must be correct?

At 25 degreees, the H value is negative

What will happen to a solution with a thermodynamically favorable reaction?

The salt will be soluble