CHEMISTRY COMMUNITY

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Use H+ to balance the hydrogen in an acidic solution but use OH- to balance hydrogens in a basic solution

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We always know that oxygen has a -2 charge and hydrogen always has a +1 charge. Regarding electrochemistry, this is important because if we are given a molecule like XO2H2 with no charge where X is an imaginary atom, we know that X must have an oxidation number of +2

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Balance all elements except oxygen and hydrogen. Then balance oxygens by adding h2o. then add twice as much h2o to the opposite Side of reaction. finally balance hydrogens by adding OH-

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when doing redox reactions it is most important to make sure the equation is balanced. First balance the important element. Then balance oxygens with H2O. and depending on if it is in an acidic or basic solution, balance hydrogens with H+ or H+ and OH-. you may put coefficients in front of everything

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Although the focus is on the molecules being reduced and oxidized, it is still a chemical reaction and all the elements and charges need to be balanced. As we have done in the past there needs to be the same number of hydrogens on both sides and electrons etc. there are two really good example probl...

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The problem normally tells you if it is happening in an acidic or basic solution

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No. When balancing a reaction happening in an acidic solution you just balance the oxygens first with h2O and then balance the other side with H+. However, in a reaction in a basic solution you still balance the O in the reaction with H2O. Next you have the add the number of hydrogens to the other s...

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if there is no change in volume then there cannot be any work done. remember, it doesnt matter how hard you push against the wall, if it doesnt move no work was done.

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entropy is a state function therefore if the initial entropy is equal to the final entropy then the delta s is 0

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Just like, look at the givens.

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use the 5/2 when pressure is constant.
use 3/2 when volume is constant.

a great example is problem 8.31 in the 6th edition

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Dr. Lavelle does a great job of providing any constants or equations we need during the test. He normally doesnt ask his students to memorize things like this.

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liquid to gas has a larger enthalpy because more energy has to be put into the system to complete that phase change. When Dr. Lavelle explained why gas burns do more damage than liquid burns it really helped me understand this.

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Joule is the SI unit but sometimes it makes more sense to use Kilo Joules for convince reasons.

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to calculate volume you multiply area x height. to calculate the area of a cylinder you would find the area of the top and multiply it by the height

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both systems can exchange heat however a closed system cannot exchange matter

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P x A x D = P x delta V

Area x distance (height )equals the change in volume. For example if you were to calculate the volume of a cylinder you would find the area of the top and multiply it by the height.

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In reversible reactions the reactants react with other reactants to form products. In a irreversible reaction the reactants react to form the products, which cannot revert back into reactants.

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blog posts are due at 11:59, like 2 minutes from now. homework is due in discussion

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you are correct. phase changes like gas to liquid are exothermic and therefore release energy.

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endothermic- products are favored by a increase in temperature
exothermic- products are favored by a decrease in temperature

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an acid donates a proton H+
a base accepts the proton

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ICE table is
initial concentration, change in concentration, equilibrium

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always use kelvins. add 273.15 to Celsius to get kelvins. remember to make sure that the temperature remains the same during the reaction/s.

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Firstly, that chemical equation is incorrect. I think the book messed up. But for part a) NO will increase
b)no, o2 will increase. think of it like a sew saw

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K is the equilibrium constant. Its value is only true once the reaction has reached equilibrium. Q can be calculated any time during the reaction. Regardless of the amount of products and reactants used, K will always be the same.

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the first bond is always a sigma and the next two after that are pi bonds

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one sigma bond and two pi bonds

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one sigma bond by default, and a pi bond because its a double

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If the acid has the same base element the strength of the oxyacid depends on the number of oxygens. If the oxyacid has a different base element the stronger oxyacid is the one with a more electronegative base.

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F is too electronegative to have HF be a strong acid. It retains the hydrogen to well and does not fully disassociate in water

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I asked my TA. She said we probably do not need to know this

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ph decreases as temperature increases. The molecular vibrations increase which results in the ability of water to ionise and form more hydrogen ions.

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The trigonal bipyramidal molecular shape normally has bond angle 90 and 120 but because the lone pairs repeal each other the bond angles are <120 and <90

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To excite an electron it must be transferred energy. When an electron returns back to its normal state, it releases energy.

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He recently posted this on his website. Test 3 covers "End of Bonding from 3.12 (6 Ed.) and from 2D (7 Ed.); and all of Molecular Shape and Structure (see Syllabus and Outlines for details)."

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It is necessary we use Kilograms when doing calculations. Equations like the momentum p=mv require the mass in kilograms.

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Yes, they are synonyms including "induced dipole induced dipole interaction." Van Der Waals forces are caused by the constant fluctuating polarizations of nearby particles causing brief attractions between molecules.

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If the electronegativity difference between the two atoms is greater than 2, it is likely an ionic bond.
If the electronegativity difference between the two atoms is less than 1.5, it is likely a covalent bond.

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Van Der Waals bonds are constantly occurring due to the fluctuating polarizations of nearby particles. Yes, two atoms experiencing hydrogen bonding can also be experiencing van Der Waals attraction.

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1.602 x 10^19 joule = 1 electron volt

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My TA told us to keep all the digits during the calculations and at the very end to consider sig figs

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Hertz means a single cycle per second

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It is the force of attraction between positive and negative charges. It is responsible for the current generated in a circuit because the free electrons in the conducting wire are attracted to the positive end of the battery.

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The discovery of the photoelectric was significant because it proved that light was not only a wavelength but also a particle. It supplied an alternative method of describing light.

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The correct order is s<p<d<f. Keep in mind that an electron traveling from d to s releases more energy than an electron traveling from f to p.

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The correct order is s<p<d<f. Keep in mind that an electron traveling from d to s releases more energy than an electron traveling from f to p.

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