CHEMISTRY COMMUNITY

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Just email the picture to your TA to get points for your 5 questions

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"The three-hour closed-book exam that was scheduled for Sunday is also cancelled.

In its place will be a short, straightforward, open-book, take-home final posted on my class website. " according to his mew email.

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As professor lavelle's email said all the review sessions and office hours are cancelled

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The email will probably be sent out tonight so we can know what to do

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How do you determine how many intermediates must form based on a reaction profile and the number of mechanism steps

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The rate law of the reaction 2 NO(g) 1 2 H2(g) S N2(g) 1 2 H2O(g) is Rate 5 kr[NO]2[H2], and the mechanism that has been proposed is 21 21 21 , the rate of the reaction is 1.21 mmol?L s . The Potential energy Step 1 NO1NO¡N2O2 Step 2 N2O2 1H2 ¡N2O1H2O A Step 3 N2O1H2 ¡N2 1H2O (a) Whichstepinthemecha...

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”The units of a reaction rate are concentration/time. This is most often M / s, where M is molarity (moles per liter) and s is time in seconds.”

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”The units of a reaction rate are concentration/time. This is most often M / s, where M is molarity (moles per liter) and s is time in seconds.”

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Q is the concentration of product over reactant in other words for galvanic cells we can write q as the concentration of anode over that of the cathode.

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Kinetic stability basically occurs when the reactants react really slowly. The slower the reaction occurs, the greater the kinetic stability. If you say, "This reaction is kinetically stable," then that implies that the reaction occurs very slowly. Thermodynamic stability depends on wheth...

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You will be handed back your test in discussion the following week but your TA might put the score online before handing it back.

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Does anyone know how to write half reactions when reducing and oxidizing agent is the same

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Can anyone explain this question to me:
What is the approximate chemical formula of rust? (b) What is the oxidizing agent in the formation of rust? (c) How does the presence of salt accelerate the rusting process?

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"A precipitation reaction refers to the formation of an insoluble salt when two solutions containing soluble salts are combined. The insoluble salt that falls out of solution is known as the precipitate, hence the reaction’s name"

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https://m.youtube.com/watch?v=DrToRsXmjP4
The youtube video explains the difference useful to know when distinguish between thermodynamic and kinetic control.

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Maintain charge balance and connect the oxidation and reduction half-cells

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The equation sheet given on the test mostly has the equations needed but sometimes you need to be able to rearrange them in order to get your desired formula .

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Hi this link is very useful in explaining the steps:
http://www.occc.edu/kmbailey/Chem1115Tu ... idized.htm

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Photon

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Attached

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I like to hear chemistry puns, periodically

It’s morning time, up and atom!

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Reactions

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If our delta g is negative then the reaction is spontaneous in the forward direction.

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For that question you have to just use STP as illustrated in the solution manual

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You can use the the ideal gas law to utilize PV instead of nRT in the case that the question only gives you the volume and pressure

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When work is done on the system it is positive and when work is done by the system it is negative

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Does anyone know which homework problem was on the midterm?

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When is deltah equal to q and when can we put q equal to deltah

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we don't get averages or distribution curve sf or the tests in this class but we will be given the averages on the midterm and final

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in a closed system, the matter is constant yet energy can be exchanged with the surroundings whereas in the isolated system neither matter nor energy is exchanged.

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since the question does not explicitly give the temorature we can assume in its ideal state that the temprature conditions are STP (298K)

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hello, does anyone know where I can find pictures of the worksheet from this step up session

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the heat lost by the ice is equal to negative the heat gained by the water. so the sign would go to water in liquid form.

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the equation sheet on the midterm is similar to the on test 1 so you should memorize the ones used for the homework problems but not stated on the sheet.

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In most of the workshops the ua's give out practice worksheets I recommend checking out the monday workshop

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Since we are talking about the ideal gas equation the n would be moles of our gas

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Ideal gas molecules do not attract or repel each other.

Ideal gas molecules themselves take up no volume.

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Use pV=nrt when plugged in you will then need to calculte the grams from the moles found using the equation

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When asked to calculate the equilibrium concentrations of the products or the reactants of a reaction we use the ICE table

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You can go from pka to ka by taking 10 to the power of negative pka and when you found ka you can easily divide 10 to the power of negative 14 by ka to get kb

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You can use kp when the reactants and products are gases and the partial pressures of the gases are given rather than their concentrations

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No
Since solids and liquids are not written in the k expression we don't need to include them in the ice tables

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The tests are more like the homework problem whereas the midterm and final have more conceptual questions

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Test one only includes outlines 1 and 2 which include the chemical equilibrium and the acid and base information from this quarter

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You will test out the two answers and the answer that is less than the initial answer will be the correct one

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ICE tables are used when the problem is only providing the initial concentrations and we are trying to find the ph or ooh of weak acids or bases

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We use kc when we are dealing with concentrations but we only use kp when we are dealing with partial pressures of gases.

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I think the best tip would be to do as many of the homework problems as possible to better understand the material and test yourself on all the material covered in lectures

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Test one starts this week in discussion sections starting on Tuesday. The test will cover the first two outlines on dr Lavelle's chem 14b website.

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Since k is a ratio constant the units of the products and reactants concentration cancel out making k a unitless constant.

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How is it that a change in concentration does not change the value of k?

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Yes, this is easily proven using the ideal gas law pv=nRT

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Since K is a ratio the threshold would depend on the molar ratio of the products and reactants given in the reaction.

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When given percentages you can easily find the moles of the products and reactants. From there you can calculate the molarity and concentration and plug it into the Kc formula to calculate the equilibrium constant of the reaction.

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it is a cumulative final from all of the 6 outlines: Outline 1: Review of Chemical & Physical Principles Outline 2: The Quantum World Outline 3: Chemical Bonds Outline 4: Molecular Shape and Structure Outline 5: Coordination Compounds and Their Biological Importance Outline 6: Acid and Base Stru...

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I attached a helpful summary of the definitions

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https://lavelle.chem.ucla.edu/wp-conten ... pounds.pdf
Dr. Lavelle sent this link and it is very helpful.

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I think we only need to memorize the strong acids and bases outlined in the table from the fundamentals section J.

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can someone please explain how to do part b and c of this homework problem? 6A.9 Which of the following can be classified as reactions between Brønsted acids and bases? For those that can be so classified, identify the acid and the base. (Hint: It might help to write the net ionic equations.) (b) NH...

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A polydentate ligand has prefixes that indicate the number of donor atoms and more than 2 lewis base sites, such as lone pair donating sites used to bond to a central atom or ion.

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https://lavelle.chem.ucla.edu/wp-conten ... pounds.pdf
Professor Lavelle emailed this list.

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look at it as a trigonal planar shape with a lone pair instead of an atom, therefore, making a bond of less than 120 degrees.

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you can lose 1-2 points for the wrong number of sig figs.

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the bent shape has 1-2 lone pairs whereas linear has 0 0r 3 in the case of I3.

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when determining the polarity we only need to take into account the electronegativity trends in the periodic table, therefore, don't need to memorize exact values.

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Hydrogen bonding is a special type of dipole-dipole in which one of the atoms is hydrogen, is covalently bonded to an electronegative atom, such as oxygen, chlorine, or fluorine.

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according to the syllabus "Each test and exam has a total score but is not assigned a grade. Only at the end of the class when the class average score (out of 500 points) is known are final grades assigned. This class does not use a curve".

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I think he will most likely give us a compound and ask us to identify its shape.

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Yes because electronegativity describes the tendency of an atom to attract a pair of electrons making it more negative.

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When energy is absorbed the delta E is positive therefore goes from lower n to higher n.

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The trend for electronegativity is the same for the trend in atomic spectra and ionization energy with some exceptions. It increases from right to left and decreases from up to down a group.

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Electrons will only be emitted if the energy of a photon reaches a certain threshold of energy. Therefore increasing the intensity will have no impact on the energy of the phon and rather the increase in frequency will increase the energy of photon therefore ejecting more electrons. This proves the ...

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C O is more polar because of the greater difference in electronegativity

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Test 2 will cover what we went over in class in outline 2 but was excluded from the midterm + what we learn after the midterm up to the test

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covalent bond: both atoms are involved in the formation of bond. coordination bond: only one atom is involved.

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the midterm is to topic 2d and according to the outline we have to be able to "List the factors affecting the covalent bond length and explain the effect of each".

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I think as long as the practice problems relate to what is being taught in lectures then it'll be sufficient for the homework.

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yes we need to know them because one of the questions on the dino nuggets midterm review sheet asked which rules were not being followed and you had to know the rules in order to answer the questions.

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the midterm will cover outline 1 (fundamentals, covered in test 1) and 2(the quantum world) completely and outline 3 (chemical bonds) up to topic 2d.

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Can someone please explain how ionization energy measured

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electron is promoted when it absorbs a photon to jump from a low energy level orbital to a higher energy level orbital

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Delocalization increases stability by resonance because it increases the bonding between atoms and spreads energy over a larger area.

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Electronegativity: tendency of an atom to attract an electron
Ionization energy: required energy to remove an electron from an atom

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The ionic radius is half the distance between atomic ions in a crystal lattice and follows trends in the periodic table.

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exceptions for electron configurations:
Cu-(Ar)3d^10 4s^1.
Cr-[Ar] 3d5 4s1

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memorization is not required and professor Lavelle will give us the required information on each test.

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I think even though we are only obliged to do 5 questions it would be better in the long run if we looked at at least half of the fundamental questions professor outline on the class website.

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I found the pre/post assessment questions to be very helpful also professor Lavelle outlined the important questions in the textbook that correspond to the topics he discussed in class.

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I suggest finding a group of people you are comfortable with and make a study group. just remember everyone gets stressed but college is the time to conquer your fears.

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The energy of a photon is equal to Planck's constant multiplied by the frequency of light. E = hf

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Increasing to decreasing:
Yrays
Xrays
Ultraviolet rays
Visible light
Microwaves

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Increasing to decreasing:
Yrays
Xrays
Ultraviolet rays
Visible light
Microwaves

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The frequency (number of waves per second) of a photon determines its energy whereas the number of photons determines the intensity of light.

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how do we determine is our answer is reasonable in "If an electron (mass 9.11 x 10-31 kg) has an associated wavelength of 7.28 x 10-9 m, what is its speed? Is your answer reasonable, why?'

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can someone explain this question to me "When neutrons pass through a crystal is a diffraction pattern observed?
What does this experiment tell us about neutrons?"

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Hello does anyone know whether our first test is multiple choice or free response?

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The mass of one mole of water is equal to 2 times the molar mass of hydrogen (2x1.008 g) plus the molar mass of oxygen (16 g) which is equal to 18.016 g. 1 mole of water is equal to 6.022 x 10^23 molecules so to find the molar mass of one molecule of water all you need to do is divide 18.016 by (6.0...

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As a confused incoming freshman hoping to pursue the pre health route, this is truly inspiring. Tahnk you for sharing.

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You can get a digital copy here:
https://ebookentry.com/product/chemical ... isEALw_wcB

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