CHEMISTRY COMMUNITY

Renee Grange 1I

What is the difference between kinetically and thermodynamically controlled?

Renee Grange 1I

Part b of Q5 on the UA worksheet. I am unclear how to write an equation that takes into account the addition of NaOH to the buffer solution. As well as how to take into account 50 mL of NaOH vs. 100 mL of acetic acid/acetate buffer.

Renee Grange 1I

How do you show the rate of change of one species in a reaction is related to another species?

Renee Grange 1I

Vertical lines are used to separate species in different states. Commas are used to separate species in the same states.

Renee Grange 1I

When there is no solid given in the cell diagram or reaction, you can always use platinum as the metal.

Renee Grange 1I

Additionally, I believe reactions have the same intermediate species whether they are going in the reverse or forward direction.

Renee Grange 1I

What factors is K dependent on?

Renee Grange 1I

I believe we can always assume the cathode is on the right side.

Renee Grange 1I

You can write the total reaction to see what the products and reactions are. But, I believe the anode is usually the product and the cathode usually the reactant.

Renee Grange 1I

What order do you put compounds in the reaction in when drawing the cell diagram? Does the order of reactants and products have any affect when drawing the salt diagram?

Renee Grange 1I

How exactly does a salt bridge work?

Renee Grange 1I

n is the number of electrons transferred. In order to calculate n, you must write the half reactions for reduction and oxidation, balance them, and then see the number of electrons transferred.

Renee Grange 1I

We use this equation when calculating delta G in standard and nonstandard conditions.
In order to calculate n, you must write the reduction and oxidation half reactions, balance them, and then observe the number of electrons transferred.

Renee Grange 1I

Do galvanic cells always have to be spontaneous?

Renee Grange 1I

Entropy = 0 in an isothermal reversible system

Renee Grange 1I

When do we need to cancel H+ with OH- when balancing redox reactions?

Renee Grange 1I

How can we tell the difference between galvanic and electrolytic cells?

Renee Grange 1I

How is platinum used in redox reactions?

Renee Grange 1I

It is 0 degrees Celsius and atm.

Renee Grange 1I

Similar to entropy and enthalpy, G knot is G at standard conditions.

Renee Grange 1I

Yes, I think you could do that.

Renee Grange 1I

Why would removing some NO (g) from the system not increase the partial pressure of NO2 (g) at equilibrium?

Renee Grange 1I

In a reversible expansion change in entropy total = 0. Therefore - ΔS surroundings = ΔS system
In an irreversible free expansion ΔS surroundings = 0 and ΔS total = ΔS system

Renee Grange 1I

More complex molecules have larger standard molar entropies because there are more possible configurations and therefore more disorder, and therefore more entropy than smaller, less complex molecules.

Renee Grange 1I

Polyprotic acids dissociate more than once. K1 is the K value for the first dissociation and K2 is that for the second dissociation.

Renee Grange 1I

∆Gº is the delta G at standard conditions

Renee Grange 1I

In this question it states 22 KJ of expansion work is done on the system by compressing it into a smaller volume.
They set +22 kJ = -P delta V
Then state -22 kJ = P delta V
Why is this step necessary? How can work be negative is the system is being compressed?

Renee Grange 1I

When does q = 0, so delta U = w?

Renee Grange 1I

Is it possible for isothermal reactions to be irreversible, if so, how?

Renee Grange 1I

We know something is a strong acid or base if it fully dissociates in water.
Some common strong acids are:
HCl4, HCl, HBr, HI, HNO3, H2SO4
Some common strong bases are :
LiOH, NaOH, KOH, Ca(OH)2, Sr(OH)2, Br(OH)2

Renee Grange 1I

You would use Cv when the system is at constant volume and Cp when the pressure is constant. For example, for a bomb calorimeter question you would use Cv because the system is at constant volume.

Renee Grange 1I

An extensive property is one that is dependent on volume/size. A state function is a function such as specific heat capacity, where the path taken does not matter only the beginning and end points.

Renee Grange 1I

We can only tell if a reaction is spontaneous based on delta S alone is delta S total > 0. This is because spontaneous reactions follow the second law of thermodynamics, which is that entropy is always increasing. If delta S total is > 0, entropy is increasing and the reaction is spontaneous.

Renee Grange 1I

Why do irreversible free expansion do zero work? ( this is used in question 4I.9)

Renee Grange 1I

What is enthalpy?

Renee Grange 1I

When do we need to use the q = C delta T equation.

Renee Grange 1I

A state function is a value that doesn't depend on path taken to obtain that state and its value is determined by its current state.

Renee Grange 1I

What is the difference between specific heat capacity and molar heat capacity?

Renee Grange 1I

An extensive property is one that depends on the amount of material. An example of this is volume.

Renee Grange 1I

From what I have in my notes I think its %=[A-]/[HA] x 100% , but I'm also confused about this.

Renee Grange 1I

When the K value is < 10^-3, you can approximate. If you approximate, you must calculate the percent ionization in order to check. This value must be less than 5%.

Renee Grange 1I

Polyprotic acids are acids that dissociate more than once. K1 is the value of K for the first ionization. K2 is the K value for the second ionization.

Renee Grange 1I

You would need to use an ice box if you are given initial concentrations and/or asked to find concentrations at equilibrium. You can just solve if the concentrations you are given are equilibrium concentrations.

Renee Grange 1I

The Ka value should be
Ka = [C6H3Co2-] [H3O+] / [C6H5COOH]
Ka = (2.64x10^-3)^2/((.110- (2.64 x 10^-3))
Ka = 6.5 x 10^-3

Renee Grange 1I

in pH/pOH the you only count sig figs after the decimal point.

Renee Grange 1I

When do we need to take into account the autoprotolysis of water needs to be taken into account?

Renee Grange 1I

The divide by 100 in order to convert pKa to bar. 1 pKa = .01 bar.

Renee Grange 1I

We are given the partial pressure in pKa on the y axis. We can use the fact that 1 pKa = .01 bar when setting up the equilibrium constant.
Kp = (Pb)(Pc)^2/ (Pa)^2
Kp = (5/100)(10/100)^2/(18/100)^2
This gives up the equilibrium constant for the reaction.

Renee Grange 1I

In an ice table, the units must be in concentrations. mols/Liter

Renee Grange 1I

For right now, we only need to use delta H to determine is a reaction is endothermic or exothermic. If delta H is positive, the reaction is endothermic. If delta H is negative, the reaction is exothermic.

Renee Grange 1I

When writing the equilibrium constant K, the stoichiometric coefficients are the exponents to the concentrations of each part of the reaction.

Renee Grange 1I

C stands for change in concentration. In the C row, you put what is left after the reaction occurs of each component. ex (initial concentration -x) or (initial concentration + x)

Renee Grange 1I

This question asks to refer to table 5G.2 to find the K value. How do you know whether to use the value listed as "K" or the one listed as "Kc."

Renee Grange 1I

Changing the concentration does not change K because although the concentrations of reactants and products will be different, the overall ration of them in the equilibrium constant will remain the same. Higher concentration of reactant will produce a higher concentration of product.

Renee Grange 1I

I think the reason you are getting the wrong answer is because you are using 1.8 bar instead of 1.18 bar, but your steps are correct.

Renee Grange 1I

We can compare K and Q values to see if a reaction has reached equilibrium or not. If Q < K, the forward reaction is still favored, and we have to wait longer for the reaction to reach equilibrium; [R] > [P] . If Q > K, the reverse reaction is favored; [P] > [R].

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