CHEMISTRY COMMUNITY

Ali Nosseir

q and delta H are equal to one another when the system is at constant pressure. q isn't a state function because q represents heat energy. If you think about water for example, water could be heated by 2 Joules by either putting it on a stove or stirring the water really fast. q=2J for the stove exa...

Ali Nosseir

Hello!
The equilibrium constant, K, doesn't actually have any assigned units.

Ali Nosseir

I think it's viable to just assume that for the reactants, the bonds are broken and for the products, the bonds are formed.

Ali Nosseir

In this situation, you'd use the Fe3+ half reaction that yields Fe(s) because the question is asking for which metal is the stronger reducing agent. The other Fe3+ half reaction yields Fe2+(aq) which isn't a solid.

Ali Nosseir

Hello! The k' comes from the relationship between the equilibrium constant K and the rate constants of the equation k. The equilibrium constant of a reaction K is equal to the k (forward reaction) over the k' (reverse reaction). In the reaction we studied in class, the K in 2K2K[NO]^2[O2] is replace...

Ali Nosseir

Delta E is the same for a catalyzed reaction and the regular reaction because catalysts don't affect the energy of a reaction but rather the activation energy of the reaction. The activation energy is the minimum amount of energy needed for the reaction to occur and a catalyst simply lowers the amou...

Ali Nosseir

Rate constant, k, is affected by both temperature and activation energy. Higher temperature causes k to increase and a higher activation energy would cause k to decrease.

Ali Nosseir

Hello! If you're given the initial rate of the reaction and the rate law, you know the order of each reactant, thus providing crucial insight on how a change of concentration will affect the reaction rate. Since A is first order, the factor the concentration is changed by will change the overall rat...

Ali Nosseir

I think Professor Lavelle said we'd never have to come up with an intermediate species on our own to determine what the rate law for a reaction is. He said most likely we'd be given a series of elementary steps for a reaction and we'd have to come up with the intermediate specie(s) from the given re...

Ali Nosseir

Hello! When including an inert metal in a cell diagram, there must be a single line separating the species reacting and the inert metal because they would be in different phases. The purpose of the inert metal is to help current flow from the anode to the cathode for a complete aqueous solution. If ...

Ali Nosseir

A redox couple as defined in the textbook is "the reduced and oxidized species in a half reaction jointly forma redox couple." The notation for a redox couple is typically denoted as (oxidized species/reduced species).

Ali Nosseir

Hello! It's necessary to put a negative sign in front of the reactant rate because we know that the concentration of the reactants must decrease for a reaction to happen, thus indicating a negative reaction rate. However, we want a positive rate, so if we place a negative in front of the reactant ra...

Ali Nosseir

Hello! The order of a reaction doesn't rely on stoichiometric coefficients. You can use the differential or integrated rate law to come up with the order of the reaction or if the question specifies a table with the changing concentrations and the respective change in the rate of the equation, you c...

Ali Nosseir

The activation energy of a chemical reaction is the minimum amount of energy a reaction needs to undergo a specific reaction whereas free energy is the amount of thermodynamic energy available for the system in the reaction to do work.

Ali Nosseir

You're exactly right! Some typical rules for finding the oxidation states of certain elements in a compound are: 1. Group 1 elements have a +1 oxidation number. 2. Group 2 elements have a +2 oxidation number. 3. O2 always has a (-2) charge (per each oxygen atom) except for when bound to peroxides wh...

Ali Nosseir

By using the equation delta G = -nFE(knot), we can see that if the E(knot) is positive, the delta G value has to be negative because the n value, moles of electrons has to be positive and F, Faraday's constant is always 96485 C. As we learned from thermodynamics, a negative delta G implies that the ...

Ali Nosseir

Since you're given the rate equation (k=[A][B]^2), we can plug in the given fractions. For example, the first part of the question asks to find the initial rate of the reaction if [A] is halved and [B] is tripled. We can interpret "halved" as "1/2" and tripled as "3" so...

Ali Nosseir

The 5% rule is applicable to the "x-is-small" approximation, indicating the absence of the minus X for the concentration of the reactants in the K equilibrium expression. In my opinion, an easier way to determine whether the (-x) is needed in the denominator of the equilibrium expression i...

Ali Nosseir

To balance the reaction, the first thing you need to do is identify the two separate half reactions, within the chemical reaction and balance the oxygen atoms on either side of the half reaction using water molecules. After balancing the oxygen atoms, since both reactions take place in basic solutio...

Ali Nosseir

Using the Nernst equation, E = E(knot) - ((RT)/(nF))ln(K), we can relate the equilibrium constant to the standard cell potential. In the equation
R = gas constant
T = temperature in Kelvin
n = number of moles of ELECTRONS.
F = Faradays constant

Ali Nosseir

It doesn't really matter at all if you're using q=mcdeltaT, you'll get the same final temperature regardless of where you put the negative sign.

Ali Nosseir

Isothermal doesn't indicate whether the system is in a closed, isolated, or open system, isothermal simply means that the temperature is constant throughout the reaction.

Ali Nosseir

Whatever species is being oxidized is the reducing agent and whichever species is being reduced is the oxidizing agent. It's the opposite because the reducing agent is the species that's bringing about reduction by donating an electron and being oxidized while the oxidizing agent is bringing about o...

Ali Nosseir

To balance the reaction, the first thing you need to do is identify the two separate half reactions, within the chemical reaction and balance the oxygen atoms on either side of the half reaction using water molecules. After balancing the oxygen atoms, since both reactions take place in basic solutio...

Ali Nosseir

Electrons flow from the anode to cathode, where the anode contains the oxidation half-reaction and the cathode contains the reduction half reaction. When delta phi is positive, electrons are flowing from the anode to the cathode.

Ali Nosseir

You can think of it in terms of the equations we use to solve for both. To solve for heat, we use q=mcdeltaT and we often set it equal to another q=-mcdeltaT to solve for a temperature difference in a system. However, for enthalpy, we can use the standard enthalpy tables or we can use bond enthalpie...

Ali Nosseir

Correct! Because of the equation delta G = -nFE, if the reaction potential is a positive number, since F and n are positive constants, delta G would have to be negative and vice versa.

Ali Nosseir

Yes, if the delta V or change in volume is 0, no work can be done.

Ali Nosseir

Both equations essentially equal the same thing it just depends whether you'd prefer using ln or log. Professor Lavelle taught today though that we can use E=E (naught) - (0.0592)/n (log Q) if the temperature of the system its at 25 degrees C.

Ali Nosseir

Qv means volume is constant, therefore, work is 0 so delta U is equal to Qv. Qp is equal to delta H because enthalpy is defined as the amount of heat released/absorbed at a constant pressure.

Ali Nosseir

Will we be given the different R value fractions for Cv and Cp during the exam or should we be expected to memorize them?

Ali Nosseir

Will we be given the different R value fractions for Cv and Cp during the exam or should we be expected to memorize them?

Ali Nosseir

The second entropy equation refers to the entropy of the surroundings as opposed to the entropy of the system for the first equation. That's why the temperature affecting each one is opposite. In general, an increase in temperature increases entropy.

Ali Nosseir

The solution manual really complicated this problem all you have to do us know that the (sum of the products enthalpy) - (sum of reactants enthalpy) is equal to the overall reaction enthalpy. It's important to note though, that you need to multiply the respective stoichiometric coefficient by the sp...

Ali Nosseir

To determine which has work done on by the system and which system is doing work, it's important to know that the change is happening at a constant temperature. Since there is no change in temperature, the change in the internal energy of the system isn't changed, therefore, since q is positive, w m...

Ali Nosseir

I've found it really useful to do all the assigned textbook problems and I'm assuming we get the same constants and equations print out sheet as we did on the first midterm and that also contains all the equations we should be expected to know for the second midterm so while doing the textbook probl...

Ali Nosseir

I feel the midterm was very content heavy, what is the best way to study this way? I noticed that by fulling understanding mathematical concepts, the conceptual questions become much easier to learn as opposed to memorizing. If you understand the reasoning behind something, there's no need to memor...

Ali Nosseir

By calculating the Gibbs free energy if an equation, we can determine the spontaneity if a reaction. If the change in Gibbs free energy is negative, the reaction is spontaneous and vice versa.

Ali Nosseir

If the temperature of a system is changing, you can use the equation S = (n)(C)(ln(T1/T2)) where C is the specific heat capacity to calculate entropy.

Ali Nosseir

By looking at the equation delta S (surroundings) = delta H (system)/ Temperature, we can see that the lower the temperature, since its in the denominator, the greater the affect the change in H would have on delta S of the surroundings.

Ali Nosseir

You can calculate the enthalpy of a reaction using three methods: 1. Hess's Law: since enthalpy is a state function, you can add up all the changes in enthalpy for each reaction within a total equilibrium reaction. 2. Bond Enthalpies: since reactions need heat to break bonds and release heat to crea...

Ali Nosseir

There can only be one equilibrium constant at a given temperature.

Ali Nosseir

In most cases, if the K1 value is greater than the K2 value, you only use the first reaction to calculate whatever is asked. This is because if the K2 value is smaller, the amount of H+ or OH- ions it creates from the reaction is so small that it barely affects the pH.

Ali Nosseir

Where are the few practice problems from the textbook that the professor posted and your TA said would be important?

Ali Nosseir

Water autoprotolysis is the ionization reaction of water denoted by:
H2O <-> H^+ + OH^-. Where Kw = 10^-14 at 25 degrees C.
The H+ and OH- concentrations are equal at 10^-7M because the pH of pure water is always 7.

Ali Nosseir

If you check under the "Welcome and Getting Started" module, the professor has linked "Chemical Principles, 7th Edition, Student Solutions Manual (Fundamentals, 1-7, 9)" which is holds the answers to all odd problems in the textbook.

Ali Nosseir

The equilibrium constant of the reaction would stay the same yet at the moment that the concentration of the reactant or product is changed, the reaction would shift one way or the other, resulting in the forward and reverse reaction rates being different for that specific time.

Ali Nosseir

Heat and temperature aren't necessarily the same thing. Something can be heated, in this case the water, without the temperature increasing. In order for an endothermic phase change to occur for any substance, the substance's bonds must be broken and to break a substance's bonds requires heat. When ...

Ali Nosseir

Heat isn't a state property because the different methods of heating something would yield different results when doing heat calculations. For example, a sample of water could be heated by either stirring it very very quickly or electrically heating it. By stirring the water, the kinetic energy is i...

Ali Nosseir

Many of the solutions to the textbook problems are also described somewhere within this website so if you can search a question within this website, you can most likely find a thoroughly explained answer to the question!

Ali Nosseir

K doesn't change when there is a change in pressure associated with volume because for example, when the volume (and pressure) of a reaction in a closed vessel is increased by adding more of another reactant, the concentration of the added reactant would obviously change, since more of it is being a...

Ali Nosseir

Whenever your K value is less than 10^4, it implies that the reaction is reactant dominated since the numerator is much smaller than the denominator. For these cases, you can ignore subtracting the x from the reactant and then just solve for the x value in the numerator using the K value given.

Ali Nosseir

The addition of an inert gas, an unreactive noble gas, wouldn't affect the concentrations of reactants and products since inert gases aren't reactive. When an inert gas is introduced to a system, it doesn't react with the reactants and products inside the vessel therefore, their concentrations aren'...

Ali Nosseir

If a reaction is endothermic, meaning it requires heat for the reaction to occur, and heat is added, the reaction would shift to favoring the products. If a reaction is exothermic, meaning it releases heat as the reaction occurs, and heat is added, the reaction would shift to favoring the reactants....

Ali Nosseir

I'm not sure if my homework on Achieve is different but for one, my concentrations for H2 and N2 and 0.8 rather than 0.7. Once you get the ICE table down and an expression for Kc, you just plug in 53.3 for Kc and your concentration values then solve for x. Your equation should look something along t...

Search found 55 matches