CHEMISTRY COMMUNITY

Diana Avalos

The overall order of a reaction is found by summing up all the of the orders of each reactant.

Diana Avalos

For this one, you would just have to multiply the rate by the stoichiometric coefficients, and change to negative for the rate of the reactants. Hope this helps!

Diana Avalos

Yes, the units of k can be used to easily determine the order of the reaction.
for 0-order, is M/s
for 1^st-order its 1/s
for 2^nd-order its 1/M*s
and finally, for 3^rd-order its 1/M²*s

Diana Avalos

This is due to the fact that reactants are being used up, hence why the rate of change of reactants is negative. Therefore, the rate of change of products is positive because products are being formed.

Diana Avalos

For this problem, you will need to use the rate law you identified which was rate= k[A]^a[B]^b[C]^c. Anything to the power of 0 is 1, so you can ignore any reactant that is zero order.
Plug in the concentrations given along with k(the rate constant)

Then you will obtain your initial rate!

Diana Avalos

The half-life equation of a first-order reaction would be t_1/2=0.693/k

Diana Avalos

0.693 comes from ln(2)!

Diana Avalos

Hello,
So in this case, the graph should have a negative linear slope (slope=-k)

Diana Avalos

It has been quite difficult in my opinion, but enjoyable!

Diana Avalos

Hello, the difference between the two are:
The average reaction rate: the reaction rate over a period of time
The instantaneous reaction rate: the reaction rate a specific point in time

Diana Avalos

You use the first one when temp ≠ 298K(25°C) or when you are trying to solve for pH, the second one is much simpler and can only be used when temp=298K(25°C)

Diana Avalos

Once you balance half of your redox reactions, you then have to ensure that the number of reduced and gained electrons are equal to each other. If not, you add a stoichiometric coefficient to obtain this. You will then know n, the number of mols of electrons transferred.

Diana Avalos

A negative ΔG and positive E_cell indicate a spontaneous reaction.

Diana Avalos

Balance your half reactions then multiply them by a stoichiometric coefficient to ensure that the same number of electrons are reduced and gained.

Diana Avalos

Hello, F is Faraday’s constant 96485!

Diana Avalos

ΔU=0 can occur in an isolated system, as w=0 and q=0 because there is no heat transfer or work being done by or on the system.

Diana Avalos

Hello,
Yes looking at ΔG can determine spontaneity.
When ΔG is negative, this means the reaction is spontaneous!

Diana Avalos

ln is log_e, and while log is usually log₁₀

Diana Avalos

It's e^{to the power of the other side}!

Diana Avalos

I recommend you to use Kelvin only. If the question asks for celsius, then convert it!

Diana Avalos

-w = work done by the system
+w = work done on the system

Diana Avalos

Sig Figs should not be as important given that our tests are multiple-choice.

Diana Avalos

Yes, a reaction is spontaneous when G is negative. This can be due to a large entropy and or a negative _deltaH(exothermic).

Diana Avalos

OIL RIG, ---> oxidation is loss of electron and reduction is gain of an electron. A reducing agent losses an electron to give to the other compound/ molecule, while the oxidizing agent gains an electron from a compound/ molecule.

Diana Avalos

The problem should specify whether the reaction occurs in an acidic or basic solution. This can be given by stating the pH or pKa.

Diana Avalos

In open systems, the reaction is not covered, for example an open beaker. Here the system can exchange matter and energy with its surroundings.

Diana Avalos

When it says work is being done by the system, the internal energy of the system would decrease and w would be negative. When its says work is being done on the system, it means the system's internal energy is raised due to the work done on it, and w here would be positive.

Diana Avalos

It's definitely endothermic as the cake batter absorbs heat (endothermic) inorder to become a solid.

Diana Avalos

Q and K have the same formula, it's just the concentration of products divided by the concentration of reactants. However, you use Q when the system is not at equilibrium as Q is not a constant. K on the other hand is a constant and is equal among all reactions regardless of the amount of moles as l...

Diana Avalos

if you remember, K_c or Q_c= [products]/[reactants]. If Q<K, this means there are more reactants and the formation of products would be favored in order to reach equilibrium. Hope this helps!

Diana Avalos

Hi, So here we say that the heat gained by the cold water = to the heat lost by the hot water q cold water = -q hot water so mC sp ΔT= -(mC sp ΔT) mC sp (T final - T initial )= -(mC sp (T final - T initial )) note that the specific heat (C sp ) of water is 4.184J/g°C Now you have to plug all you kno...

Diana Avalos

R is a constant meaning its true value doesn't change, however, it could change if you are using different units

Diana Avalos

Work is positive when work is done on the system and negative when work is done by the system

Diana Avalos

You first have to look for the chemical reactions that have the products and reactants from your reaction of interest. You would probably start by choosing from reaction 1 or 4, though 1 would be the best as 4 has MCl 3 on both sides. As you probably noticed, in 1 you are missing Cl 2 on the reactan...

Diana Avalos

Determining whether heat is added(endothermic) or removed(exothermic) from a system is a much simpler way to tell if its endothermic or exothermic.

Diana Avalos

The equation you should use here is ΔH_RXN=ΔH_f(products)- ΔH_f(reactants)

Diana Avalos

I believe it has not been assigned.

Diana Avalos

Melting(also known as fusion) is an endothermic phase change as energy(heat) is required for a solid to become a liquid!

Diana Avalos

Freezing is an exothermic phase change as it liquid releases energy to become a solid!

Diana Avalos

Sublimation is an endothermic phase change as it requires heat(energy) to go from a solid to gas. Deposition (gas to solid) would be an example of an exothermic phase change.

Diana Avalos

Condensation is an exothermic phase change as it releases energy to go from a gas to a liquid!

Diana Avalos

Freezing, deposition, and condensation are examples of exothermic phase changes!

Diana Avalos

The temperature of interest refers to the temperature at which the reaction is occurring. I lectures, Professor Lavelle has stated that if temperature is not sated, you can assume temp = 25°C

Diana Avalos

Work is the transfer of energy from one system to another!

Diana Avalos · Re: Week Start/End Monday -Sunday 11:59pm

Monday -Sunday 11:59pm

Diana Avalos

They are all equilibrium constants,
ka is for acids, kb is for bases, and kc is for concentrations

Diana Avalos

Since enthalpy(H) is a negative value, this means it's exothermic, meaning the reverse reaction would be favored so reactants are favored.

Diana Avalos

Ka is the equilibrium canstant, its Kb for the base, and pKa is the -log of pKa, and pKb is the negative log of Kb

Diana Avalos

Q is the ratio of products/reactants when it's not in equilibrium, if its in equilibrium we use K

Diana Avalos

Both are used to describe the same thing, lies/shifts/sits to the right means the products are favored, and lies/shifts/sits to the left means the reactants are favored

Diana Avalos

You can know the sign of x given the information provided. Say if it says there were more products added, then it would be -x on the products side as the reverse reaction is favored in reaching equilibrium. This means there will be a +x on the reactants for this case.

Diana Avalos

You can use it to convert molar concentration (n/v) to partial pressure or convert partial pressure to molar concentration.

Diana Avalos

You can use it to convert molar concentration (n/v) to partial pressure or convert partial pressure to molar concentration.

Diana Avalos

R is a gas constant, Dr. Lavelle used it in the Audio-Visual Focus modules.

Diana Avalos

Like everyone said it depends on the information given. For molar concentrations it's Kc and for partial pressure, it's Kp.

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