CHEMISTRY COMMUNITY

Tiffany Cao 1D

When there are two of the same products being produced, will the rate law always have a coefficient of 2?

Tiffany Cao 1D

When a system expands reversibly, does that only mean that change in entropy of the total system and surroundings is 0?

Tiffany Cao 1D

If we use the equation, Ecell=Ecellnaut - (RT/nF)(lnQ), for this problem, how do we solve for what n is?

Tiffany Cao 1D

When calculating pseudo equilibrium constants, why do we use delta G (dagger) rather then just the usual delta G?

Tiffany Cao 1D

For practice example 8.5 on page 274, why did we assume that delta U was 0 in the second step of part B?

Tiffany Cao 1D

In what cases will delta U be 0?

Tiffany Cao 1D

At 0 Kelvin, why does NO have a higher residual entropy then BF3?

Tiffany Cao 1D

Can catalysts appear in an overall rate law?

Tiffany Cao 1D

Can we assume the rate law for individual elementary reactions? For an example, if a slow elementary reaction is 2I+H2==>2HI, is the rate law=k[I]^2[H2}?

Tiffany Cao 1D

For #89, how do we know which step is the slow step when none of the rates match the experimental rate given?

Tiffany Cao 1D

In practice example 15.7, on page 636, I used the pre equilibrium concept and got a similar answer to the book, which used the steady state concept. However, I don't really understand how the 2 appeared in the overall rate of decomposition of O3. In the previous example in the book, they used the un...

Tiffany Cao 1D

How do we draw the proposed structure for an activated complex, as asked in problem 15.85?

Tiffany Cao 1D

For this problem, why can we assume that rate constant is directly proportional to rate?

Tiffany Cao 1D

For problem 15.67, is it correct to just plug in the actual rates into the equation rather than using the the relationship between Ea,cat and Ea,uncat. I just used Ae^(-75/RT)/ Ae^(-125/RT) and got the same answer.

Tiffany Cao 1D

Does expansion against a external pressure imply constant pressure?

Tiffany Cao 1D

The rate of a reaction can never be negative. Basically, since its a rate of consumption, the overall is negative to make the final minus initial part positive.

Tiffany Cao 1D

Why are we allowed to assume that fast reaction mechanisms will not have an effect on the overall rate law?

Tiffany Cao 1D

When finding the rate constant, should we convert all time units to seconds?

Tiffany Cao 1D

Does the order of the cathode and anode matter in our cell diagrams? Especially when there is an H+ present.

Tiffany Cao 1D

When do we include H+ when writing cell diagrams? In 14.23, part a,in what order should we write the reactants in the cathode side?

Tiffany Cao 1D

For problem 14.21, a solid electrode is not given on the electrode side. How do we go about answering this problem?

Tiffany Cao 1D

In problem 13, part d, how do we know which side is the cathode and which side is the anode?

Tiffany Cao 1D

Given a cell reaction, like in example 14.13, how do we know which is the cathode and which is the anode?

Tiffany Cao 1D

When there is no salt bridge, how do we know which element gets reduced and oxidized. In practice example 14.4 on page 576(not the actual homework problems), I don't understand how they assumed the reduction or oxidation of the half reactions.

Tiffany Cao 1D

What does it mean to say that something is an oxidizing or reducing agent. I noticed that in the first couple questions, that when electrons were added in half reactions, the solution would call that an oxidizing agents. But in later sessions, when electrons were lost, it was through an oxidation pr...

Tiffany Cao 1D

I don't really understand how tot do cell diagrams. How do we know which element gets reduced and how do we organize the diagram?

Tiffany Cao 1D

When balancing charges in the half reactions, why do we not make the charges on both sides equal each to each other?

Tiffany Cao 1D

Why delta S of the surroundings 0 in an isothermal, free expansion process?

Tiffany Cao 1D

Am I right by saying that if volume does not change,if a gas expands in a vacuum, and if a gas undergoes free expansion, work is 0?

Tiffany Cao 1D

When a process is reversible, is deltaS of the system 0 or is delta S total 0?

Tiffany Cao 1D

If using molar heat capacity, do we need to convert temperature to Kelvin?

Tiffany Cao 1D

Is delta U also 0

Tiffany Cao 1D

In an isothermal, free expansion system, work is 0. However, this is only true for the surroundings, as can be seen in practice example 9.12 on page 346. Why is work not 0 for the system too?

Tiffany Cao 1D

When a system is reversible, does that mean that only change in total entropy is 0? How about change in internal energy?

Tiffany Cao 1D

Does a system do work when a piston expands isothermally in a vacuum?

Tiffany Cao 1D

How is heat being transferred in an isothermal system?

Tiffany Cao 1D

Well in order to use the formula, s=klnw, you need to know the number of orientations of a compound. To solve for degeneracy, I use # of orientations^# of molecules.

Tiffany Cao 1D

Delta U is the change in internal energy. It is calculated through the formula, DeltaU=q+w. In an isolated system, deltaU=0 and consequently, w=-q.

Tiffany Cao 1D

In what real life scenarios would Gibb's free energy be negative?

Tiffany Cao 1D

In which cases would we use 3/2*R=Cv and 5/2*R=Cp? I noticed in 9.43, the solution used the actual heating capacity of water(75.29J/Kmol), but when would we ever use the other heating capacity rules?

Tiffany Cao 1D

When a system is heated, experiences an increase an volume, or a decrease in pressure, entropy increases. In what other scenarios will entropy increase?

Tiffany Cao 1D

If there was a there is a change in volume and pressure, would we use Cv or Cp to calculate entropy?

Tiffany Cao 1D

What exactly does Gibbs Free Energy measure?

Tiffany Cao 1D

On page 329, why do we use 127J/Kmol as the heating capacity for heating up liquid acetone but 133.26 J/Kmol (4R) when cooling down vapor acetone?

Tiffany Cao 1D

For problem 9.19, why do we also cool the system? Aren't we just find entropy change of vaporization?

Tiffany Cao 1D

The second law of thermodynamics states that entropy will increase when spontaneous actions occurs, such as gas expanding in a vacuum. Basically in the equation, nrln(V2/V1) and cln(T2/T1), if V2 and T2 are bigger than V1 and T1, entropy will increase. If V1 and T1 are bigger than V2 and T2,, entrop...

Tiffany Cao 1D

Why do we use Cv instead of Cp when calculating entropy change in relation to temperature change?

Tiffany Cao 1D

Calculating enthalpies using bond enthalpy is the least accurate method since this method uses the average bond enthalpies. Because of this, bond enthalpies are not specific to certain molecules.

Tiffany Cao 1D

How do you find the change in entropy when dealing with an irreversible system?

Tiffany Cao 1D

When calculating total entropy change of a process, like in Practice Example 9.5 on page 325, we use the change in entropy equations of both volume and temperature changes. For the second portion, why do we use the change in entropy equation when temperature changes with heat capacity that relates t...

Tiffany Cao 1D

Im asking for practice example 9.5

Tiffany Cao 1D

When calculating total entropy change of a process, like in example 9.5 on page 325, we use the change in entropy equations of both volume and temperature changes. For the second portion, why do we use the change in entropy equation when temperature changes with heat capacity that relates to when vo...

Tiffany Cao 1D

For problem 9.13, why do we use the change in entropy=nRln(T2/T1) instead of the change in entropy=nCv(T2/T1)?

Tiffany Cao 1D

When a system is isothermal, does that mean that temperature is constant? Why does this also mean that change in internal energy is also 0?

Tiffany Cao 1D

Which equation do we use for change in volume? Change in temperature? And change in pressure?

Tiffany Cao 1D

Why is using bond enthalpies the most unreliable form of calculating reaction enthalpy?

Tiffany Cao 1D

If asked to give the amount of heat RELEASED by a chemical reaction, would the answer be positive or negative?

Tiffany Cao 1D

What if you were given the specific heating capacity which is measured in J/g*C, but asked to find final temperature in K. Are Celsius and Kelvin used interchangeably in this case?

Tiffany Cao 1D

Is standard enthalpy of formation essentially the same as reaction enthalpy, but with molecules in their most standard form?

Tiffany Cao 1D

Given the equation for a thermodynamic reaction and bond enthalpies for each bond, can we find the standard enthalpy of formation or just the reaction enthalpy. For an example, 8.67 asks for enthalpy of formation and 8.73 asks for reaction enthalpy, but they both used bond enthalpies in the same way.

Tiffany Cao 1D

Since enthalpy is essentially heat (which is measured in kJ), it doesn't really matter if you use kJ/mol or kJ for enthalpy.

Tiffany Cao 1D

Can we assume that enthalpy of reaction(change in enthalpy) is the same as heat transferred(q)?

Tiffany Cao 1D

When can change in internal energy be equaled to heat transferred? When can it be equaled to work?

Tiffany Cao 1D

What is the relation between change in enthalpy and change in internal energy?

Tiffany Cao 1D

When finding enthalpies of reactions, what are the indicators that will show you when to use Hess's Law, Bond Enthalpies, or Standard Enthalpies of Formation?

Tiffany Cao 1D

In example 8.13 on page 301, why is the enthalpy of vaporization of Br2 positive while enthalpy of vaporization of CH3ChBrCH2Br is negative?

Tiffany Cao 1D

In example 8.53, why do we use q=C(change in T) rather than q=mC(change in T)?

Tiffany Cao 1D

In a heating curve, the enthalpies of fusion and vaporization are depicted as straight, horizontal lines. However, which element or characteristic of the heating curve gives information about heat capacities?

Tiffany Cao 1D

Temperature stays the same during phase changes, such as melting and vaporization, because all energy added is being used to break up the bonds rather increasing temperature.

Tiffany Cao 1D

How do you find enthalpy of vaporization if a question does not give you the enthalpies of either vapor or liquid. In self test 8.9A on page 284, is the heat added to the system equal to the enthalpy of vaporization?

Tiffany Cao 1D

In an exothermic reaction when temperature doubled, what happens to the K constant and why?

Tiffany Cao 1D

How does the reaction quotient differ from the K constant?

Tiffany Cao 1D

How does partial pressure affect equilibrium ?

Tiffany Cao 1D

Why do some conjugate acids gain H while others gain OH

Tiffany Cao 1D

In an endothermic reaction, heat is required to break bonds, so endothermic reactions favor a reverse reactions. Do endothermic reactions, then, also favor the formation of reactants? In class, it was said that endothermic reactions favor product formation ???

Tiffany Cao 1D

I noticed that K was written out in brackets [X] or in parenthesis with P (Px). What is the differentiation?

Tiffany Cao 1D

In this case oxygen has a tetrahedral molecular shape, but a bent VESPR geometry. The two lone pairs aren't directly 180 degrees from each other, but 109.5, so they don't really cancel the effects of each other out. Because of this, they push the remaining bonds closer together, and thus they become...

Tiffany Cao 1D

What are polydentates and how are they related to ligands. How does CO3^2- in example 17.33 have polydentate ligands?

Tiffany Cao 1D

Why are pi bonds weaker than sigma bonds even though they make double bonds stronger?

Tiffany Cao 1D

In hybridized orbitals s and p orbitals combine, or hybridize. When an element makes a single bond, that becomes a sigma bond. Every second or third bond is a pi bond.

Tiffany Cao 1D

How do lone pairs influence the shape of the molecule?

Tiffany Cao 1D

What elements can hold less or more than an octet? Do all of their orbitals need to be filled as well when drawing Lewis dot diagrams?

Tiffany Cao 1D

For compounds such as ClONO2, how will we be able to determine which element is in the middle and the overall organization of the Lewis structure?

Tiffany Cao 1D

How do we know when to create a double or triple bond? Would it be okay to just leave a Lewis structure consisting of single bonded elements if all elements had an octet?

Tiffany Cao 1D

When can an element have both covalent and ionic bonds? Or is this impossible?

Tiffany Cao 1D

Do we need to include d-block elements when counting the number of valence electrons?

Tiffany Cao 1D

What concept of the Shrodinger Equation is necessary to know for the test?

Tiffany Cao 1D

When will the energy for 4s be less than 3d?

Tiffany Cao 1D

When writing out electron configurations, why can't you just write out 2p^2, instead of 2px^1 2py^1. Are they both the same configurations?

Tiffany Cao 1D

What is Hund's rule and how is it relevant to electron orbitals? What would happen if the orbitals had opposite spin?

Tiffany Cao 1D

In the function, Ek=hv-(work function), how would we solve for the work function? In addition, if the work function exceeds the kinetic energy, does this mean the photon is not able to be emitted from the piece of metal?

Tiffany Cao 1D

I am uncertain how to derive the DeBroglie Equation from the E=mc^2 equaiton. Is it necessary to know how to derive this function?

Tiffany Cao 1D

An empirical formula is just the ratio of the atoms in a reaction, whereas an molecular formula shows the actual number of atoms in a reaction. In order to calculate a molecular formula, you first must calculate the empirical formula by dividing the given mass by the molar mass to find the amount of...

Tiffany Cao 1D

What is the difference between theoretical and percentage yield, if there is a difference? Also, what causes the theoretical yield to be less than the actual yield?

Search found 94 matches