CHEMISTRY COMMUNITY

Jessica Wakefield 1H

For part c of 8.93 you have to calculate the change in internal energy of the system using your answers from part a and b. The value of w you find in part a is +3.72 kj/mol and the value of dH you find in part b is -3267.5 kj/mol and for c you are supposed to get -3263.8 kj/mol but I was wondering w...

Jessica Wakefield 1H

temperature and activation energy

Jessica Wakefield 1H

because your integrated rate laws can be viewed in the form of y=mx+b and k is in the place of m, you regard k as your slope. depending on the order, k will be positive or negative.

Jessica Wakefield 1H

unless the question specifically asks for you to convert the units, then you should be fine just solving in whatever units are given

Jessica Wakefield 1H

because depletion of A is proportional to generation of B, we use the increase in B given and convert it to moles of A by multiplying .018 by 1/3 (because the ratio of A/B is 1 mole to 3 moles). After doing this we subtract this value from the initial to get the new value of [A] or [A]t. then you ju...

Jessica Wakefield 1H

not necessarily because aA is in terms of just moles while concentration is in molarity which is moles per liter so they may not be directly proportional, though they could be

Jessica Wakefield 1H

They converted the values to mol from mmol before calculating but I would assume that you wouldn't have to do this unless the question specifies that the answer should be converted since they didn't convert for #17

Jessica Wakefield 1H

we want to find the order of a reaction because it shows how the concentration of the reactants affects the rate, therefore we can develop a better understanding of the rate of the reaction

Jessica Wakefield 1H

if your concentration doubles and your rate doubles as well, the interaction is proportional and thus the order is considered first in this problem they said that when concentration is increased by 1.2 the rate does as well and also when the other concentration is doubled the rate does as well, demo...

Jessica Wakefield 1H

moles because the concentration is molarity which is mol/L
if youre given grams you have to convert to moles and then divide by the amount of liters to find the concentration

Jessica Wakefield 1H

yes because your reaction rate is in reference to speed so the value should be positive

Jessica Wakefield 1H

the rate you find for 2NO2 would be the unique rate multiplied by two because there is 2 moles of NO2 so to find the unique rate you would just divide by 2

Jessica Wakefield 1H

they can refer to each reactant separately or to the reaction of the whole. the sum of each of the reactants' orders is the order of the whole reaction.

Jessica Wakefield 1H

to determine the units of k you set up the equations rate=k[A] Because the units for rate are M/s and the units for concentrations is just M you divide rate by [A] to get k alone and solve for the units of K you end up doing M/s * 1/M and depending on the n for the given problem your answer will be ...

Jessica Wakefield 1H

How do you know which element is oxidizing and which is reducing? It looks like they are both gaining electrons so I'm confused.

Jessica Wakefield 1H

Why is the sig figs for #19 only one instead of two?

Jessica Wakefield 1H

This questions asks whether a crystal of octahedral cis-MX2Y4 would be expcted to have the same, higher, or lower residual entropy than the corresponding trans isomer and the solutions manual explains that the cis would have higher residual entropy and proves it mathematically but could this higher ...

Jessica Wakefield 1H

For part b of 9.47, how do you know dU=0?

Jessica Wakefield 1H

The solutions manual states that the reasoning for container A having higher entropy is because it has a greater number of particles that B or C. Are we supposed to assume that B and C are also gases but because they contain diatomic molecules they have less entropy or are they not gases and the fac...

Jessica Wakefield 1H

When I try to raise 6 to the power of 6.02x10^23 my calculator just says error. Does anyone have any advice/is anyone having the same issue?

Jessica Wakefield 1H

Kb is 1.381 x 10-23 J/K

Jessica Wakefield 1H

Kb is Boltzmann's constant, so it is 1.381 x 10-23 J/K but you can still solve part a even if you didn't know that because Kb is multiplied by ln 1 which is 0 so your answer is 0 regardless

Jessica Wakefield 1H

During the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5*C was compressed suddenly (and irreversibly) to 0.500 L by driing in a piston. In the process, the temperature of the gas increased to 28.1*C. Assume ideal behavior. What is the change in entropy of the gas? I was wonde...

Jessica Wakefield 1H

Hydrochloric acid oxidizes zinc metal in a reaction that produces hydrogen gas and chloride ions. Apiece of zinc metal of mass 8.5 g is dropped into an apparatus containing 800 mL of 0.500 M HCL(aq). If the initial temperature of the hydrochloric acid solution is 25*C, what is the final temperature ...

Jessica Wakefield 1H

Hydrochloric acid oxidizes zinc metal in a reaction that produces hydrogen gas and chloride ions. Apiece of zinc metal of mass 8.5 g is dropped into an apparatus containing 800 mL of 0.500 M HCL(aq). If the initial temperature of the hydrochloric acid solution is 25*C, what is the final temperature ...

Jessica Wakefield 1H

for problem 8.93, to calculate work they used a formula w=-PdV and because no volume was given they used -P(dnRT/P) and I was wondering if the delta n is used because the original formula calls for delta V and therefore there just needs to be a change in one of the elements in PV=nRT because of the ...

Jessica Wakefield 1H

An ideal gas in a cylinder was placed in a heater and gained 5.50 kJ of energy as heat. If the cylinder increased in volume from 345 mL to 1846 mL against an atmospheric pressure of 750 Torr during this process, what is the change in internal energy of the gas in the cylinder? I was wondering why wh...

Jessica Wakefield 1H

What does it mean if an equation is isothermal? Is the deltaU definitely going to be 0 or is that only under certain conditions?

Jessica Wakefield 1H

What does it mean if an equation is isothermal? Is the deltaU definitely going to be 0 or is that only under certain conditions?

Jessica Wakefield 1H

Can someone explain why heat is not a state property. I understand why enthalpy (qp) is a state property but want to know why heat itself (q) isn't.

Jessica Wakefield 1H

you could but for our purposes, i think we are only concerned with 2-4

Jessica Wakefield 1H

Exothermic and exit start the same so its like the heat is exiting the system and Endothermic is just the opposite so it absorbs the heat or heat is put into the system

Jessica Wakefield 1H

An open system can be a hot cup of water as long as it's not insulated (not in a thermos or sealed vacuum flask)

Jessica Wakefield 1H

When setting up an ice table for 11.67, why does the solutions manual go from original to new initial? Why do you subtract 1 bar from each of the products and add a bar to the reactant. I don't understand why you wouldn't use the original values that the problem gives you.

Jessica Wakefield 1H

The solutions manual gives an answer talking about how nitrous acid is strong and how nitrous acid's Ka will increase and the answer for carbonic acid is that it is a weak acid and thus has no effect on equilibrium. the question just asked whether they would be strong or weak acids. Why is the answe...

Jessica Wakefield 1H

a) Nitrous acid and carbonic acids are both weak acids in water. Will either of them act as a strong acid in acetic acid? Explain. When finding the answer for this, do you need to compare how acidic each acid is in acetic acid to how acidic they are in water or is the info about them being weak in w...

Jessica Wakefield 1H

Background for the question: Ka=18, Kb=5, Kc=10 and the balanced equation is 2A->B+2C
K=Pb(Pc)^2/(Pa)^2

I had solved it by (5)(100)/324

The solutions manual says it should be (5/100)(10/100)^2/(18/100)^2 or (0.05)(0.01)/(0.0324)

final answer= 1.54x10^-2

Jessica Wakefield 1H

For part B in 11.89, when calculating the equilibrium constant for the reaction, the solutions manual says that the values for Pk should each be divided by 100 before being used for (Pb)(Pc)^2/(Pa)^2. Why do we need to divide by 100 (5/100,10,100, and 18/100) first vs just using the values in the ch...

Jessica Wakefield 1H

A reaction mixture consisting of 2.00 mol CO and 3.00 mol H2 is placed in a 10.0 L reaction vessel and heated to 1200 K. At equilibrium, 0.478 mol CH4 was present in the system. Determine the value of Kc for the reaction CO(g)+3H2(g)<>CH4(g)+H20(g) at 1200 K. Does anyone know why you don't convert t...

Jessica Wakefield 1H

The solutions manual says that 4.25b is nonpolar.

Jessica Wakefield 1H

The Lewis structure for part a of 4.23 (OSbCl3) shows Sb as the central atom with four single bonds and O has 3 lone pairs. Would an acceptable structure also be a double bond for O and 2 lone pairs or is there a specific reason why O has 3 lone pairs and not 2?

Jessica Wakefield 1H

For part d on problem 4.13, I got the lewis structure for N2O wrong. I had the structure as N-N=O with a lone pair over the central N because I thought this was the most stable structure. All the atoms have a formal charge of 0. However, the correct structure is either N=N=O or N(triplebond)N-O. I w...

Jessica Wakefield 1H

Indicate whether there must be, may be, or cannot be one or more lone pairs of electrons on the central atom: 0--0--0 linear structure with 180 degree bond angles----> may have one or more lone pairs can anyone explain to me why it is possible that it could have lone pairs? I had assumed that would ...

Jessica Wakefield 1H

Hi the solution manual shows a lewis structure for SCl4 rather than SF4 for part D. Just wanted to confirm it would be the same structure just replaced with F rather than Cl? Or would it be slightly different?

Jessica Wakefield 1H

Which element in each pair has the lower electron affinity?

P or S

I chose S on the test because it is in the same group as O and so I assumed it behaved the same way? Can someone just clarify why it is that P is the correct answer.

Jessica Wakefield 1H

After boasting your excellent bowling skills with your custom made 4.32 kg ball, you demonstrate your fastest bowl, rolling the ball down the lane at 9.23 +/- 0.1 m/s. What is the minimum indeterminacy of its position. Can you blame the Heisenberg Uncertainty Principle when you have a gutterball? I ...

Jessica Wakefield 1H

forgot to include the rest of the problem:

Given 0.036 g of methane and 0.108 g of water, how much hydrogen, in grams, is produced?

Jessica Wakefield 1H

Hi I'm not really sure how to address the two-step reaction when attempting to solve limiting reactant problems. Can someone help me with this example please.

Step 1: CH4+H20 ---> CO+3H2
Step 2: CO+H20 ---> CO2+H2

Jessica Wakefield 1H

In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line. I read a few replies to questions on 1.15 from other students but I am sti...

Jessica Wakefield 1H

For copper the electron configuration is [Ar] 3d10 4s1. The exception is that the 3d comes before the 4s because the d sub-level is more stable than a partially filled d sub-level.

Jessica Wakefield 1H

Are px, py, and pz considered subshells or is p itself considered a subshell?

Jessica Wakefield 1H

I think it will cover everything we've discussed in lecture last week and what we will discuss this week.

Jessica Wakefield 1H

When writing e- configurations, would you always shorten it with the last element in the previous row and then add on from there?

Jessica Wakefield 1H

Which of the following happens when the frequency of electromagnetic radiation decreases? C. the extent of the change in the electrical field at a given point decreases. Could someone explain what is meant by "the change in the electrical field." I got the right answer for this question by...

Jessica Wakefield 1H

I have been using 3.00 for the most part and it hasn't caused any error. All of my answers have been accurate and as long as you show your work on the tests/quizzes, you shouldn't lose any points for using one versus the other.

Jessica Wakefield 1H

Over the summer, I reviewed some high school chemistry concepts using Khan Academy. They have videos that I found helpful because it is more engaging than reading from a textbook or attempting to teach yourself. They have pretty much any topic you might want to review and it is not too time consumin...

Jessica Wakefield 1H

To prepare for our test yesterday, I used the modules and also took notes on the suggested textbook readings. I think that taking notes on the textbook sections aided in my understanding in addition to the modules. I did find the modules more helpful and more engaging, though.

Jessica Wakefield 1H

To prepare for our test yesterday, I used the modules and also took notes on the suggested textbook readings. I think that taking notes on the textbook sections aided in my understanding in addition to the modules. I did find the modules more helpful and more engaging, though.

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