CHEMISTRY COMMUNITY

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a decrease in pressure means an increase in volume.

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was the equation given on the equation sheet on the midterm? I dont recall it being given

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at STP, you simply input the standard temperature and pressure into the equation: 1 atm and 273 degrees kelvin. Then you may proceed with the problem as normal

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Using pv=nrt, I determined that n=0.003mol. However, when I put that into the equation w=-nRTln(v2/v1), I get -3.18J, which is not possible since an isothermal reversible expansion always does more work than an irreversible one. Can anyone determine what I did wrong? I'm having trouble figuring it o...

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I'm a bit confused as to where the given temperature comes in

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A piece of copper of mass 20.0 g at 100.0 8C is placed in a vessel of negligible heat capacity but containing 50.7 g of water at 22.0 8C. Calculate the final temperature of the water. Assume that no energy is lost to the surroundings. Im a bit confused on how to proceed with this problem. I used q=M...

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partial pressure is specifically the pressure of a specific gas in a mixture or reaction, whereas pressure is the pressure of the entire reaction.

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no, not for calculating work.

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you need to plug the equation into PV=nRT in order to proceed with this problem since it is stated in the problem that it is an ideal gas. Thus, for constant pressure you solve for the P and for constant volume you solve for the V.

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usually the phase change will be given in the question and you just apply it as needed

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why do we need to add the specific heat capacities? and how are we supposed to assume this is a composite system? im working on this question right now and im also wondering if we add the specific heat capacities of water and copper in one equation or do two separate equations?

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(a) Calculate the heat that must be supplied to a copper kettle of mass 400.0 g containing 300.0 g of water to raise its tem- perature from 20.0 8C to the boiling point of water, 100.0 8C. (b) What percentage of the heat is used to raise the temperature of the water? I am slightly confused on how to...

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how do you go about the conversions for this problem? the answer is given using L times atm.

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Jasmine Fendi 1D wrote:Enthalpy is just the measure of heat! Temperature and enthalpy are related but are different, as seen in heat curves. The x-axis is heat supplied and the y-axis is temperature

How are heat and enthalpy different?

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Can someone please explain why we do final minus initial when doing state properties?

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No. The heating curve introduced in lecture is specific to only water

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In lecture, Professor Lavelle asked why steam causes severe burns, and proceeded to show the heat curve. Can someone explain the heating curve and what it means?

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yes, cooling will favor the products!

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If Kp is given rather than Kc in a problem but the product is given in moles or grams rather than bars, how do you proceed with the problem? how can you convert to pressure?

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At 25 8C, K 5 3.2 3 10234 for the reaction 2 HCl(g) ∆ H2(g) 1 Cl2(g). If a reaction vessel of volume 1.0 L is filled with HCl at 0.22 bar, what are the equilibrium partial pressures of HCl, H2, and Cl2? Do we need to set up an ice box with the partial pressure of HCl although it is given in partial ...

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A reaction mixture consisting of 2.00 mol CO and 3.00 mol H2 is placed in a reaction vessel of volume 10.0 L 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) 1 3 H2(g) ∆ CH4(g) 1 H2O(g) at 1200. K. Can someone explain ho...

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K does not have units. because it is a ratio of products to reactants, and is a constant in the reaction. Also, if you worked out the math in an equilibrium problem K = [P]/[R], and so the molarities cancel out.

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The reason solids are not used in equilibrium reactions is because their concentrations stay constant throughout the reaction

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Yes, gases are included in the gas phase. H20 in the liquid phase is not used because they do not affect the reactant amount at equilibrium.

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Kp and Kc are both calculated in the same way. However, Kc is denoted when a problem is given using molar concentrations, and Kp is denoted when a problem is given using pressures of a gas

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Q can be used whether or not the reaction is at equilibrium, and is used to determine whether or not a reaction is in equilibrium. K can only be used when a reaction is in equilibrium. Both are calculated in the same way.

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Because more moles of O3 are placed in a container of the same volume in the second experiment, the partial pressure of O2 will be higher. This is because the Kp must be the same, so the pressure of O2 of the second experiment must be higher to maintain the same Product to reactant ratio as the firs...

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the conjugate base is the product you have after your acid gives off a proton; the conjugate acid is what product you have after your base accepts a proton.

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count the sig figs AFTER your decimal :)

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are these memorized or should we be able to explain these?

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The hydrogen bonding od DNA Base pairs, heme as a coordination compound, cisplatin for chemotherapy, vitamins as acceptors of dangerous radicals, the role of carbon dioxide in blood ph These are the examples i can think of can you elaborate on the vitamins? So as you already know, radicals contain ...

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the hydrogen bonding of base pairs, edta, hemoglobin and myoglobin, cisplatin v translation as an effective chemotherapy drug.

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They are the same things, however hexadentate is a more specific and accurate response especially for edta since we focused on it so much!

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Its not chemotherapy's structure, it's the structure of the chemotherapy drug known as cisplatin. Cisplatin has two chlorines on the same side that attach to the guanine base pairs of a DNA molecule, allowing for a stronger bond to block DNA polymerase from replicating a cancerous DNA strand. Transp...

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sigma bonds are able to rotate already!

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make sure that the anion has more than one hydrogen!

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it would make the emission of energy negative, as it is emitting more than it already has when a photon is emitted.

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Which of the following increase when the electron in a hydrogen atom undergoes a transition from the 1s-orbital to a 2p-orbital? (a) Energy of the electron. (b) Value of n. (c) Value of l. (d) Radius of the atom. Can someone explain part d of this problem? what does the radius of the atom have to do...

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A molecule that is a Lewis acid can also be considered a Bronsted acid (and vice versa) since their definitions do line up. In order for a molecule to accept an electron pair (be a Bronsted acid), it donates a proton (is a Lewis acid). Typically you can use both definitions to define an acid unless...

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Can someone explain the difference between bronsted and Lewis acids and bases, and also conjugate? I dont understand the differences between them

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Can someone explain the difference between bronsted and Lewis acids and bases, and also conjugate? I dont understand the differences between them

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On the basis of the expected charges of the monatomic ions, draw the formula unit of each of the following compounds using Lewis symbols: (a) thallium(III) chloride; (b) aluminum sulfide; (c) barium oxide.

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Yes, with a nitrogen, oxygen, or fluorine

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The following species have the same number of electrons: 1 21 Cd, In , and Sn . (a) Write the electron configurations for each species. Explain any differences. (b) How many unpaired elec- trons, if any, are present in each species? (c) What neutral atom, if 31 any, has the same electron configurati...

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memorization in this situation will help - the chart in the textbook provides the shapes along with their polarities.

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Lewis bases will typically contain the lone pair to donate to the Lewis acid

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You can determine ionic bonds by their electronegativity differences: if the difference is over 2, it is considered ionic.

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The number of lone pairs (more electrons) increases polarizability thus a higher melting point.

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The orientation of the orbitals will be facing outwards, so 120 degrees

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Always look at the symmetry of a molecule first. If a molecule is symmetrical, it is non polar. If not, find the Mose electronegative atom and that is the slightly negative end of a polar molecule

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A higher polarizability indicates a higher melting point since it has higher intermolecular forces

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Can someone explain T shape and give an example of a molecule with the T shape?

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Simply look at the. lone pairs and bonds in the molecule top determine your answer

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The shape of the orbitals is octahedral. One orbital contains a lone pair of electrons so the remaining five atoms connected to the central atom gives the molecule a square pyramidal shape

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A t shaped has three bonds and two lone pairs, as discussed in section 2E of the textbook.

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Incomplete octets can occur when elements do not have enough electrons to complete an octet around each element, even with double or triple bonds.

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Incomplete octets can occur when elements do not have enough electrons to complete an octet around each element, even with double or triple bonds.

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H bonding is not as strong because it is less of a bond and more of an attraction between the slightly negative and slightly positive sides of molecules.

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Its a lot of commitment, with the studying from 14B and the hours spent in lab. Its suggested you take them separate quarters, or even better, take the lab during summer if you can!

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Larger atoms means more electrons meaning more shielding can occur

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The first four elements will never have an octet. P,Cl, and S will typically break the octet

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Its always one or the other. Elements like P,CL, and S typically break the octet rule

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Antioxidants give an e- to a radical to stabilize it. Foods like dark berries contain a lot of these and are critical in a balanced diet to stabilize free radicals in the body.

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find the wavelength of light equal to the work function

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Hydrogen bonds are the weakest amongst the bonds. Ionic is next strongest, and covalent bonds are the strongest bonds

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A bowling ball of mass 8.00 kg is rolled down a bowling alley lane at 5.00+/- 5.00m/s. What is the minimum uncertainty of its position?

When given a +/- in speed, how do we proceed with the problem?

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The most stable structure is that with the lowest formal charge. So while multiple structures may be drawn, there is typically one with the lowest formal charge that is accurate.

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The midterm covers everything from fundamentals to 2D in the homework assignments and readings.

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The octet rule mainly only applies to atoms with less electrons. As the atomic number increases, the atom is more capable of having more than an octet.

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Electronegativity decreases down a group and across a period, so just look at the positions of the elements on the periodic table.

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How does P violate the octet rule? does it have a valence shell of 10?

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Since each orbital holds two electrons, the d-orbital has 5, allowing for ten total electrons.

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If the uncertainty was too large, the equation would essentially be useless

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since oxygen has a smaller radius, its electronegativity is higher!

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Why does ionization energy decrease as shells fill up?

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I'm still confused on why the 4s group comes before the 3d group from Dr. Lavelle's lecture, can someone explain why and for what situations this applies?

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What exactly does ground state electron configuration mean? What is it asking me to find?

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i believe this is how you do it: a) 103 because ml can be any value between [-l, l] so there are 51*2+1 possible orbitals bc) 1 because they give you a ml value so there's only one possible orbital d) if n=57 then there are 57 possible l values and for each of them they'd have l*2+1 orbitals (or ju...

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when the energy of the photon of the energy required to eject the electron from the metal, the electron will be ejected from the metal!

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you must multiply by 10^3 to convert to the correct units

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since wavelength=h/mv, the object must have a mass. While Light has a velocity, it does not have a mass to calculate

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Can anyone help with this problem?

How many orbitals can have the following quantum numbersinanatom:(a)n53,l51;(b)n55,l53,ml 521; (c)n52,l51,ml 50;(d)n57?

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Gamma Ray, X ray, Ultraviolet, Visible spectrum, Infared, Microwave, Radio

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Gamma Ray, X ray, Ultraviolet, Visible spectrum, Infared, Microwave, Radio

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The 100-gram trick essentially simplifies calculations when given percent compositions of elements in a molecule. What you do, is convert the mass percentages to grams (as if out of 100) and divide by the molar masses in order to find the moles of each element and be able to determine your ratios fr...

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Yes, since the limiting reactant is the product that is not in excess, it is the product that will be completely used up and therefore determines the maximum (theoretical) yield that can be produced.

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Always stay consistent with the units given to you in the problem, but always remember that you may have to convert some units in order to fit into the problem (such as converting milliliters to liters to find molarity.) However if an answer seems too small or too large for a given unit, feel free t...

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the $\mu$ represents the prefix micro-, thus the term meaning micrometer, which is $10^{-6}$ meters

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With sig figs, use the exact values you calculate until you reach your final answer. Then, round to the same number of sig figs as the values given in the problem. If the value is below five, round down. If the value is five or above, round up to the net nearest integer.

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With sig figs, use the exact values you calculate until you reach your final answer. Then, round to the same number of sig figs as the values given in the problem. If the value is below five, round down. If the value is five or above, round up to the net nearest integer.

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