CHEMISTRY COMMUNITY

Taha 2D

for exothermic reaction, when the temp increases, equilibrium shifts to reactants (left) to decrease K
-for endothermic reactions: when temp increases, equilibrium shifts to products (right) to increase k

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it will depend on the units given to you in the question. you can use either but its more efficient to use the one matching the questions units so you wont have to convert anything

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it would be the reciprocal (1/k)

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because it doesnt change enthaplies. the difference in energies remain the same, only the activation energy peak is brought down

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If Q is less than K, then the equilibrium shifts to the right or makes more products. On the other hand, if Q is greater than K, then the equilibrium shifts to the left or makes more reactants.

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it keeps the solutions neutral by allowing anions and cations to pass

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they are biological catalyst because they lower activation energy and allow reactions to happen at body temp withouth getting used up

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free energy is gibbs
activation energy is the energy required to start a reaction

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it is the one shown in the rate law

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the intermediate shows up on the right whilst catalyst on left, both cancel out tho

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organic chem tutor

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the reactants shown to be in the rate law are the ones which are involved in the slow step

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physics 5a and chem c over the summers

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changing the temperature can change the rate constant

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it measures the hydrogen ion concentration in a solution and thats helpful when you need to find concentrations, equilibrium constants etc

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it increases the rate for exo or endo reactions but increasing the temp for an exo reaction would favour the reactants side of the reaction

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the moles of electrons transferred are found through the balancing of the redox reactions

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because they are on both sides of the equation so they dont contribute to the rate law calculations

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since its not used up in the reaction itll show up on both reactants and product side but wont be expressed in the overall chemical expression

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the better its reduction potential the better itll be as an oxdizing agent

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the salt bridge allows the current to flow as it connects the two cells. The anions are negatively charged so they move towards the positive anode to give their electrons (oxidize) and vice versa

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anode is where oxidation occurs because the anode is positive and thus gains electrons from the negative ions. cathode is where reduction happens due to the opposite being true

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You can tell it is basic because the cation is Na and that is a specatator ion. the proton transfer is just the anion pulling a hydrogen from water and leaving OH- What is a spectator ion and how are we supposed to identify it? Was it ever mentioned in one of the lectures? it is mentioned somewhere...

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the anode should be on the left and cathode on the right but you should be able to tell for sure by which side of the battery its connected to

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its best to think of them as opposites as in a reducing agent gets oxidized and vice versa

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just think of them as doing the opposite. a reducing agent reduces by getting oxidized and vice versa

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yes they are. A good way to remember them is if you can carry out their calculations by just doing final - intial

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It is unstable if the gibbs free energy is positive

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it depends on the units you used to solve the question. the two options are R= 8.314 J/mol.K or R= 008206 L.atm/mol.K

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No they are different but Both contribute to the internal energy of a system

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the constant temp would mean it is reversible

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a state function is one in which the pathway of the energy is not important, rather where it begins and ends

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it refers to reactions in which volume is kept constant

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K is a unit of temperature known as kelvin. K in equilibria is effected by temp as in an endothermic reaction increasing the heat will favor the product and the other way around for exothermic

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you can use either +273 or +273.15

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ya any ta can pull up ur exam questions

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CV is the amount of heat energy that a substance absorbs or releases (per unit mass) with the change in temperature where a volume change does not occur. cp is the same but when the pressure does not change. the formula relating them would be CP – CV = R

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The entropy of an object is a measure of the amount of energy which is unavailable to do work. Entropy is also a measure of the number of possible arrangements the atoms in a system can have. In this sense, entropy is a measure of uncertainty or randomness. So every reaction is increasing entropy no...

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when the system is providing energy to the surroundings it is negative as energy is essentially lost from the system, its positive when the surroundings do work on the system.

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since hbr is a strong acid it means that the Br- ion disassociates completely and thus does not effect h30 or oh concentrations meaning ph is unchanged

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1 mole on the left and 2 on the right because only gases are counted

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it is included if its in the gaseous state

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kelvin is used

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if everything (rectants/products) are in gaseous states then KP is used, otherwise KC

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Its up to your TA, some take points per week(5 before sunday midnight) and some look at your total posts

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Hbr is stronger because the bond length is longer
hclo2 after drawing the lewis you will notice the bond is cl-o-h and the cl is more electronegative than br so the h is more easily disassociated.

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You can tell it is basic because the cation is Na and that is a specatator ion. the proton transfer is just the anion pulling a hydrogen from water and leaving OH-

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lewis acids are e- acceptors, bronsted are proton donators
lewis bases are e- donors, and bronsted bases are proton acceptors
all bronsted are lewis but not the other way around

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KCl, LiBr are neutral
k2s03 and na2s are basic
nh4br is acidic

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10^-ph

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just look at whats inside the square brackets. the numbers of atoms/molecules connected to the tm cation indicate coordination number.

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number of electron density= number of hybrid orbitals
3 densities=sp2
4 densities= sp3
5 densities = sp3d
6= sp3d2

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Calculating individual formal charges will show it to be neutral

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When a compound is amphoteric, it means it has both basic and acidic character. Thus, when the compound reacts with an acid, it shows that it's basic. When it reacts with a base, it shows that it's acidic. When a compound is amphiprotic, it means it can act as a proton donor and as a proton acceptor.

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For shapes you should just know the shapes according to the number of electron densities. And yes to be safe know the bond angles as i doubt there will be a chart (in the lectures he mentioned you should be able to figure out which shape will have larger/smaller angles which can be deduced but its h...

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Myoglobin is a protein found in muscle tissues and it acts as a reservoir for oxygen. Hemoglobin is made up of 4 heme groups which are like myoglobin as they carry oxygen.

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the ligand donates both electrons thus its a coordinate covalent bond with the tm cation

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yes they are the same as one is an electron donor(lewis) and the other a proton acceptor(bronsted) which is basically the same thing. All Bronsted acids are lewis base but the reverse isn't true.

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Depends on their shape as well and if the dipoles cancel or not

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The number of regions of electron density = hybrid orbitals needed. 3= sp2, 4=sp3,

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the VSEPR model is used to determine the shape

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Sigma and pi bonds are chemical covalent bonds. Sigma and pi bonds are formed by the overlap of atomic orbitals. Sigma bonds are formed by end-to-end overlapping and Pi bonds are when the lobe of one atomic orbital overlaps another. Sigma bonds are usually stronger but you can only have one sigma bo...

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for the first two cases thats the structure which allows them to be the furthest apart. With 4 there are shapes which can maximize the distance between the atoms which is caused by the unique repulsion between the atoms(tetrahedral which is 109.5 which is greater that 90).

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sigma bonds are single bonds. You can only have one sigma bond. Sigma bonds have symmetrical electron densities allowing rotation of atoms which are bonded and share electrons through end to end overlapping along the internuclear axis. Pi bonds have a central node where there is no electron density ...

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An example to explain is benzene. When sp2 hybridization takes place a p orbital is left on the carbon. In benzene when theres a ring of carbons each with a p orbital which overlap each other a molecular orbit is formed. The electrons can travel through these orbits which span the width of the molec...

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Axial bonds alternate up and down, and are shown "vertical". Equatorial groups are approximately horizontal, but actually somewhat distorted from that, so that the angle from the axial group is a bit more than a right angle

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Polar molecules occur when there is an electronegativity difference between the bonded atoms. Nonpolar molecules occur when electrons are shared equal between atoms of a diatomic molecule or when polar bonds in a larger molecule cancel each other out.

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cations are smaller than their atoms(they lose their valence shell)
anions are larger than their atoms
size increases down the group and decreases across

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best way to see the difference is that a lewis acid accepts electrons while a lewis base donates them

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its determined by the difference in electronegativity. generally if the difference is less than 0.5 then its non polar covalent, if its 0.5-2 then its covalent but with increasing ionic character, and if the difference is more than 2 then it can be considered ionic

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lone pair electrons cause repulsion and change the shape of the molecule.

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A lewis acid is an electron acceptor while a lewis base is a donater.

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They both should have dipoles independant of each other and need to have a significant difference electronegativity to form dipole interactions.

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They are always present as intermolecular forces but they arent significant unless they build up.

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Yuehan_Wu_3K wrote:The photon has a mass even though it's very small. It should not be ignored.

from what I've read online it seems that a photon doesnt have 'rest mass' because its never at rest but since it has energy it has mass. I guess i dont understand what rest mass refers too

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So I asked my TA and he said, 'For the chemistry community, you cannot make up points retroactively by posting more'
he said theres a max of 5 points per week

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If I missed the first week or so of posts on chem community, can i make up for the points by posting additional posts?

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I am confused as to how photons have momentum since they dont have a rest mass. (p=mv)

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Why should you never trust atoms??

because they make up everything!

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these arent octet electrons. in the case of an expanded octet a valence shell can hold more than 8 electrons if they have the subshells available(as in the case of sulfur in s03. to understand look at the periodic table. chlorine falls unders group 17 and period 3. n=3 means quantum number L can be ...

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yes, increased distance from the nucleus means less electrostatic attraction from the protons. And for London dispersion forces the further the electrons are, the more freely they can move (higher polarizability) thus being able to create temporary dipoles with more ease. But keep in mind london dis...

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hydrogen bonds occur between hydrogen and oxygen,nitrogen or fluorine.

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the way it was calculated is well beyond our scope but the experiment which found out about the number 1/2 is the Stern–Gerlach experiment(experiment with the deflected silver atoms discussed briefly in a lecture). Spin is known as intrinsic angular momentum and its not actually referring to particl...

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We dont need to specific bond lengths but we should know that in resonance hybrid structures all bond lengths are equal(average of the different lengths) and the higher the electron density of the bond, the shorter the bond length

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Doctor: Your body has run out of magnesium
Me: 0mg

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Double and triple bonds have more electrons, so they exert a stronger attractive force on the nuclei of the bonding atoms, which pulls the atoms closer together and leads to shorter bond lengths

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Carbon dioxide is a polar molecule whose positive center is on the carbon atom: This positive center is able to attract (and accept) the lone electron pairs present on the oxide ion (O2-). Thus, carbon dioxide is acting as a Lewis acid and the oxide ion is acting as a Lewis base.

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It depends on the imbalance of electrons and protons. For example Chlorine has 7 valence electrons and 7 protons. When it reacts with anything, Sodium for example it creates NaCl. That means sodium with 1 valence electron bonded ionically with chlorine by giving its valence electron away. This leave...

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So metals(elements on the left side) are more likely to form cations ( positively charged ions) because of their number of valence electrons. The left hand side normally goes up till group 3 meaning they have upto 3 valence electrons. So all atoms are looking to form full valence shells. For metals ...

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theres no set order you have to follow but its the easiest to balance the elements which occur the least on both sides of the equation.

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significant figures are mainly used to calculate the uncertainty of the result you obtain. They shouldnt be varied in your calculations and throughout the question the same number of significant figures should be considered.

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The equations are given but knowing them gives a big edge because you can immediately understand what needs to be used and its also a confidence booster.

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1/wavelength= rydberg constant (1.0974*10^-7) * (1/2^2 - 1/1^2)

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They are the same thing and refer to the minimum energy required to excite an electron to the point it leaves the surface. Different substances have different values and if energy lower than the threshold is supplied nothing substantial will occur.

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I was having the same problem. Whenever the special text box shows up at the bottom and you are dealing with a molecular/emperical formula problem the keyboard won't let you type in the symbols for elements unless you type in caps.

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The convention is to make sure all the moles are whole numbers because it doesn't make sense to have quarter a mole or something of that sort.

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I personally like to balance the elements of which there are only one on both sides first and then proceed.

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They're important to uphold precision and accuracy but along with that it helps you keep track of your working because it is recommended to use the same sig figs as the given raw data. Along with that they're important when it comes to calculating the uncertainty of your final results.

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Empirical formulas need to have a whole number of moles and thats why 1.33 moles had to be multiplied by 3. 3.99 is very close to 4 so it can be rounded up. And since we need to multiply one elements moles, we need to multiply every elements moles by 3.

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