CHEMISTRY COMMUNITY

Andy Liao 1B

14.5 Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in basic solution. Identify the oxidizing agent and reducing agent in each reaction. (a) Action of ozone on bromide ions: O3(aq) + Br-(aq) -> O2(g) + BrO3-(aq) I was wo...

Andy Liao 1B

I understand that the Nernst Equation is being used to solve for E in part (D). However, I don't understand how the answer key arrived at 1/(1*10^-16) for Q. Can someone please explain? Also, I'm sorry. The image automatically flipped when I posted it

Andy Liao 1B

IMG_8952 2.jpg Problem: (m) Which reactions could be described as kinetically controlled? I was wondering why (2) and (4) could be described as kinetically controlled. What about these two reactions makes them kinetically controlled? Why aren't (1) and (3) kinetically controlled? Can someone please...

Andy Liao 1B

15.65 For the reversible, one-step reaction 2A ⇌ B + C, the forward rate constant for the formation of B is 265 L.mol^-1.min^-1 and the rate constant for the reverse reaction is 392 L.mol^-1.min^-1. The activation energy for the forward reaction is 39.7 kJ.mol^-1 and that of the reverse reaction is ...

Andy Liao 1B

15.85 The following rate laws were each derived from an elementary reaction. In each case, write the chemical equation for the reaction, determine its molecularity, and draw a proposed structure for the activated complex: (a) Rate = k[CH3CHO] (Products are CH3 and CHO.) (b) Rate = k[I]2[Ar] (Product...

Andy Liao 1B

15.65 For the reversible, one-step reaction 2A ⇌ B + C, the forward rate constant for the formation of B is 265 L.mol^-1.min^-1 and the rate constant for the reverse reaction is 392 L.mol^-1.min^-1. The activation energy for the forward reaction is 39.7 kJ.mol^-1 and that of the reverse reaction is ...

Andy Liao 1B

We compare Experiments 1 and 4 to find the order with respect to C because [A] and [B] are the same concentration in both (10. mmol.L^-1 and 100. mmol.L^-1, respectively). We know that [C] is independent of the rate because even though the concentration of C in Experiment 4 is different from the one...

Andy Liao 1B

Yeah, sorry. I meant the ratios (3.02^b / 1.25) and (50.8 / 8.7). I mixed up part (b) and part (c). Thank you!

Andy Liao 1B

Problem: 15.23 Determine the rate constant for each of the following first-order reactions, in each case expressed for the rate of loss of A: (c) 2A -> B + C, given that [A]0 = 0.153 mol.L^-1 and that after 115 s the concentration of B rises to 0.034 mol.L^-1. I know which equation to use and unders...

Andy Liao 1B

I have a general question about the order with respect to each reactant. I was wondering, if you solve for the order with respect to a reactant and get a number like 1.89 or 2.11, can you round up or round down, respectively, to 2? For example, in problem 15.19 (a), when solving for the order with r...

Andy Liao 1B

I was wondering what the statement "the reaction rate only depends on [R], the concentration of the reactant" means. Can someone please explain? I thought the reaction rate also depends on factors such as the rate constant k and the activation energy.

Andy Liao 1B

Problem: 14.13 Write the half-reactions, the balanced equation for the cell reaction, and the cell diagram for each of the following skeletal equations: (b) Ce4+(aq) + I-(aq) -> I2(s) + Ce3+(aq) I was wondering why Pt(s) is needed as an inert electrode on the anode side of the cell diagram even thou...

Andy Liao 1B

Cl- is a spectator ion, whereas O2- is not. A spectator ion exists in the same form on both the reactant and product sides of a chemical equation, so when writing a net ionic equation, spectator ions found in the original equation are ignored.

Andy Liao 1B

Problem: 14.37 Determine the potential of each of the following cells: (c) Pt(s) | Cl2(g, 250 Torr) | HCl(aq, 1.0M) || HCl(aq, .85M) | H2(g, 125 Torr) | Pt(s) The cathode half-reaction for this cell reaction is 2H+(aq) + 2e- -> H2(g). I was wondering where the Cl from the HCl went. Can someone pleas...

Andy Liao 1B

Problem: 14.33 (a) The standard Gibbs free energy of formation of Tl3+(aq) is +215 kJ.mol-1 at 25°C. Calculate the standard potential of the Tl3+/Tl couple. (b) Will Tl+ disproportionate in aqueous solution? I don't understand why in the solutions manual the equation of interest is 3Tl+(aq) -> 2Tl(s...

Andy Liao 1B

Problem: 14.11 Write the half-reactions and the balanced equation for the cell reaction for each of the following galvanic cells: (d) Pt(s) | O2(g) | H+(aq) || OH-(aq) | O2(g) | Pt(s) I was wondering how the solutions manual found the cathode and anode half-reactions for the cell reaction. The catho...

Andy Liao 1B

9.85 Potassium nitrate dissolves readily in water, and its enthalpy of solution is +34.9 kJ.mol-1. (a) Does the enthalpy of solution favor the dissolving process? (b) Is the entropy change of the system likely to be positive or negative when the salt dissolves? (c) Is the entropy change of the syste...

Andy Liao 1B

Problem: 9.101 A heat pump heats a house in winter by extracting heat from the cold outdoors and releasing it into the warm interior. For the transfer of a given amount of heat, (a) how do the entropies of the interior and exterior of the house change (increase or decrease)? (b) Which change is grea...

Andy Liao 1B

I know that by definition, residual entropy is entropy at T=0K. However, I don't understand how this statement conceptually makes sense. Can someone please explain?

Andy Liao 1B

In Chapter 9, Section 7, the book writes "S(T) = S(0) + ΔS(heating from 0 to T) = ΔS(heating from 0 to T)" and "S(T) = area under graph of CP/T against T from 0 to the temperature of interest?" What do these two expressions mean? Can someone please explain?

Andy Liao 1B

Can someone please explain to me the concept behind the Clausius inequality? The Clausius inequality is ΔS ≥ q/T. Also, what does the statement "with the equality valid for the reversible process" mean?

Andy Liao 1B

There are four steps that need to be done to find the entropy of transition at a temperature other than the transition temperature. If vaporization is involved, you first have to heat the liquid to its normal boiling point (ΔS = Cln(T2/T1)). Then, you have to allow it to vaporize (ΔSovap = ∆Hvap/Tb)...

Andy Liao 1B

I was wondering what the statement "Entropy is a measure of unavailable energy" means. Can someone please explain? Thanks.

Andy Liao 1B

Can someone please explain why more entropy is favorable over less entropy? I can't seem to grasp the logic behind the idea that disorder is more favorable than order. Thanks.

Andy Liao 1B

When writing the thermochemical equation with enthalpy of formation/combustion, the molecule of interest must be set to 1 mole. In other words, the stoichiometric coefficient in front of it must be 1. This is because the enthalpy of formation/combustion is in terms of per 1 mole of the molecule of i...

Andy Liao 1B

I was wondering if delta H and q are ever interchangeable. Are there certain circumstances that allow for them to be? Can someone please explain? Sometimes in the solutions manual, delta H is used instead of q, like for example, in problems 8.37 and 8.45.

Andy Liao 1B

Problem: Use the bond enthalpies in Tables 8.6 and 8.7 to estimate the reaction enthalpy for (b) CH3CHCH2 (g) + H2O (g) --> CH3CH(OH)CH3 (g) I don't understand how the solutions manual determines which bonds to break and form. For this problem, 1 mol of C=C bonds and 1 mol of O-H bonds are broken an...

Andy Liao 1B

Problem: Calculate the standard enthalpy of formation of dinitrogen pentoxide from the following data, 2NO (g) + O2 (g) --> 2NO2 (g) DH = -114.1 kJ 4NO2 (g) + O2 (g) --> 2N2O5 (g) DH = -110.2 kJ and from the standard enthalpy of formation of nitric oxide, NO (see Appendix 2A). I was wondering why &q...

Andy Liao 1B

I was wondering if resonance in molecules affects bond enthalpies. If so, how does it affect bond enthalpies? Can someone please explain?

Andy Liao 1B

Intensive properties do not depend on the amount of matter that is present whereas extensive properties do depend on the amount of matter that is present. Examples of intensive properties include boiling point, color, and odor. Examples of extensive properties include volume, mass, and size. It is g...

Andy Liao 1B

First and foremost, the definition of the standard enthalpy of formation of a substance is the enthalpy change when, at a pressure of 1 bar and a temperature of 25 °C, 1 mol of the substance is formed from the most stable form of its elements. The standard enthalpy of formation of an element in its ...

Andy Liao 1B

Problem: 12.63 The percentage deprotonation of benzoic acid in a 0.110 m solution is 2.4%. What is the pH of the solution and the Ka of benzoic acid? I understand how to solve the problem. However, in the solutions manual, it says H2O + octylamine ⇌ octylamineH+ + OH-. What does this mean? Can someo...

Andy Liao 1B

Problem: 12.69 Calculate the pH of each of the following solutions: (a) 0.19 m NH4Cl(aq); (b) 0.055 m AlCl3(aq). In the solutions manual, the proton transfer equilibria for part (a) is written as NH4+ (aq) + H2O (l) ⇌ H3O+ (aq) + NH3. Why isn't it NH4Cl (aq) + H2O (l) ⇌ H3O+ (aq) + NH3Cl- (aq) inste...

Andy Liao 1B

Problem: Determine which acid in each of the following pairs is stronger and explain why: (a) HF or HCl; (b) HClO or HClO ; (c) HBrO2 or HClO2; (d) HClO4 or H3PO4; (e) HNO3 or HNO2; (f) H2CO3 or H2GeO3. I was wondering why for part (a) HCl is the stronger acid. I thought that because F has a greater...

Andy Liao 1B

Problem: 11.81 A gaseous mixture consisting of 2.23 mmol N2 and 6.69 mmol H2 in a 500.-mL container was heated to 600. K and allowed to reach equilibrium. Will more ammonia be formed if that equilibrium mixture is then heated to 700. K? For N2(g) + 3 H2(g) ⇋ 2 NH3(g), K = 1.7 x 10^3 at 600. K and 7....

Andy Liao 1B

You can always try drawing out lewis structures and seeing if the compound can give, receive, or both give and receive lone pairs. If it can do both then its amphoteric. That's how I'd go about it - I dont really know of any other way. How can you tell by looking at the lewis structure if a compoun...

Andy Liao 1B

Problem:
11.29 If Q = 1.0 for the reaction N2(g) + O2(g) -> 2NO(g) at 25°C, will the reaction have a tendency to form products or reactants, or will it be at equilibrium?

Can someone please explain how to calculate K in this problem?

Andy Liao 1B

Yes, if the central atom were to form a double bond with the oxygen, the structure would be more stable due to the lowering of formal charge. However, regardless of which structure is drawn, the shape of the molecule stays the same. OSbCl3 is tetrahedral.

Andy Liao 1B

By definition, ligands act as Lewis bases, which are electron pair donors. Ligands have at least one donor atom with an electron pair used to form covalent bonds with the central atom. They bind to Lewis acidic centers, which accept electron density.

Andy Liao 1B

First and foremost, hybridization is defined as the mixing of atomic orbitals into new hybrid orbitals. These hybrid orbitals have different energies, shapes, etc., than the component atomic orbitals. Take for example CH4. In a CH4 molecule, the four H atoms form four equivalent bonds. In each of th...

Andy Liao 1B

Can someone please tell me how to clearly differentiate between electronic geometry and molecular geometry? Sometimes I mix the two up.

Andy Liao 1B

Whether the bond angle is less or more depends on whether there are lone pairs or not. This is because lone pairs strongly repulse not only each other but also other atoms within the molecules. In the case of O3, the central O has a lone pair and two bonding pairs. The repulsion between the bond pai...

Andy Liao 1B

I was told that nitrogen can form only up to three bonds. However, in the case of N20, N forms a triple bond with the second N (the central atom) and that second N (the central atom) forms a single bond with the O. Why is this true?

Andy Liao 1B

I remember hearing in lecture that Cl can form an expanded octet. However, I was told that this wasn't possible. Can someone explain or give an example of when Cl forms an expanded octet?

Andy Liao 1B

I don't really understand why the orbital energies for many-electron atoms are higher than the orbital energies for a hydrogen atom. Can someone please explain?

Andy Liao 1B

What is the difference between the atomic radius and ionic radius of an element?

Andy Liao 1B

How do you determine if an electron will spin up or spin down?

Andy Liao 1B

How is the Shrodinger Equation used?

Andy Liao 1B

Problem: Calculate the frequency of light emitted by a hydrogen atom when an electron makes a transition from the fourth to the second principal quantum level. I know that to solve this problem, we first use the empirical formula for a H-atom to solve for the energy of the electron in energy levels ...

Andy Liao 1B

Problem: When the energy per photon is equal to the energy required to remove an electron what is this energy called? A. Binding energy B. Threshold energy C. Transition energy D. Excitation energy E. None of the above I was wondering what the difference is between binding energy and threshold energ...

Andy Liao 1B

I noticed that for questions asking us to write the balanced equation, the answers in the solutions manual included physical states. I was wondering if we are expected to know how to determine the physical states in a chemical equation. Also, how exactly do you determine the physical states in a che...

Andy Liao 1B

The problem is: G.21 A solution is prepared by dissolving 0.500 g of KCl, 0.500 g of K2S, and 0.500 g of K3PO4 in 500. mL of water. What is the concentration in the final solution of (a) potassium ions; (b) sulfide ions? I know that to find the total moles of K+ in the solution, you have to first fi...

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