CHEMISTRY COMMUNITY

Aili Ye 4L

A is the pre-exponential factor, a constant for each chemical equation which shows the frequency of collisions in the correct orientation.

Aili Ye 4L

Intermediates are form and then used up so they are not part of the overall reaction and therefor rate law as well

Aili Ye 4L

The integrated rate for a first order reaction is A= -kt + Ao which is in the form of a linear equation where -k is the slope.

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Thermodynamics deals with the spontaneity of a reaction whereas kinetics deals with the speed of a reaction.

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Thermodynamics deals with the spontaneity of a reaction, whereas kinetics deal with the speed of one.

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Activation energy is the energy needed to turn reactants into products. It is the energy difference between the energy of the reactants and the highest peak of the energy graph.

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The compound that oxidizes (oxidizing agent) is the one that itself gets reduced, and vice versa.

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The H+ would be with the Cr2O7 since the oxygen atoms in it are balanced with H20, and the H20 are balanced with H+

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You can balance both initially using H+, but if you are balancing in a basic solution you must add OH- to neutralize the H+

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It is an inert electrode.

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The standard cell potentials is for reduction. That reduction occurs at the anode so we do not flip the sign.

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The other inert conductor is graphite (carbon).

Aili Ye 4L

Here's a more detailed explanation taken from Lavelle's Chem 14B Solution Manual Errors 6th Edition pdf: "Students are asked to rank the delta S for a series of gases during a temperature change. ∆S = nCv ln(T2/T1) for an isochoric process Gas A (1.00 mol monatomic ideal): ∆S = nCv ln(T2/T1) = ...

Aili Ye 4L

n is the number of molecules, not atoms, so in this case n would be 1.

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W (degeneracy) is calculated by the number of microstates/equal energy conformantions to the power of the number of molecules. S (entropy) is thus equal to the Boltzmann's constant multiplied by lnW.

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An isochoric process is a thermodynamic process in which volume is constant.

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The enthalpy of combustion is the energy released when one mole of a compound is burned in oxygen, whereas the enthalpy of formation is the change in enthalpy when one mole of a substance is formed from its constituent elements in their standard state.

Aili Ye 4L

The degree symbol means that the reaction is taking place under STP (standard temperature and pressure) conditions.

Aili Ye 4L

As the other person mentioned, standard enthalpy of formation and bond enthalpy is different. Bond enthalpy cannot be zero since all bonds require energy to break.

Aili Ye 4L

Double and triple bonds don't have the bond enthalpy equal to double or triple that of a single bond, so you must calculate single and double bond breaks differently.

Aili Ye 4L

Enthalpy is a thermodynamic measure of the total heat of a system. Change in enthalpy is thus changes in internal heat of the system.

Aili Ye 4L

Look at the Ka, the larger the Ka the more favored the dissociation into H₃O⁺ and the stronger the acid. Or look at pKa- the smaller the pKa the stronger the acid.

Aili Ye 4L

Na is simply a spectator ion in the reaction and thus isn't necessarily included.

Aili Ye 4L

pKw at 25 degrees IS 14.

Aili Ye 4L

Yes, only weak acids and bases use the equilibrium arrow. Strong acids and bases are considered 100% ionization in water thus only use one arrow

Aili Ye 4L

This takes into consideration the Chatelier’s principle which states that whenever a system in equilibrium is disturbed the system will adjust itself in such a way that the effect of the change will be reduced or moderated. Increasing or decreasing the temperature will make the system favor either t...

Aili Ye 4L

No, there isn’t such a thing as “concentration of a single molecule”. You should find the concentration overall of the molecule and take into consideration the stoichiometric coefficients is different reactants and products when calculating unknown concentrations though.

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Since that equation is the addition of two previous equations whose K eqs are given, the K eq value of the total equation is the product of the two previous Keqs.

Aili Ye 4L

We do not include liquids and solids because by convention the values in the calculation of the K expression change over time. The concentrations of solids and liquids do not change.

Aili Ye 4L

We don't include liquids and solids because by convention the values in the K expression change over time, and the concentration of liquids and solids do not change.

Aili Ye 4L

I believe we do.

Aili Ye 4L

The three chlorine atoms are more electronegative and thus pull electrons towards it. This weakens the bonds between the O and H and thus this acid would lose an H more easily, making it a stronger acid.

Aili Ye 4L

Double arrows show that the reaction can proceed both forwards or backwards depending on the equilibrium constant.

Aili Ye 4L

The angles are just 90 degrees on the equatorial plane since repulsion from the lone pairs cancel out.

Aili Ye 4L

The way I look at it is to envision the shape and look at its symmetry. Usually non-symmetric shapes with lone pairs are polar, and symmetric shapes without lone pairs or have lone pairs that cancel each other out (as in the example of a square planar molecule) are non-polar.

Aili Ye 4L

Just refer to the model when answering the question. VSEPR model is just the formula and shape and angles. We should not need to know how to draw it out.

Aili Ye 4L

Polarity depends on symmetry of the molecule. Sometimes lone pairs can cancel out, such as in the case of AX4E2, which is square planar. Since the lone pairs are directly opposite each other, the repulsion caused by them cancel out, and thus the atoms remain in a symmetrical position.

Aili Ye 4L

The structure would be trigonal planar if the lone pair did not exist. But the existence of the lone pair creates repulsion and takes up more space than an atom would and thus this would push the other molecules into a pyramidal shape.

Aili Ye 4L

Often, the lone pair can distort the symmetry and will create a polar molecule, but it is not always the case.

Aili Ye 4L

Thank you!

Aili Ye 4L

The angle remains 90 degrees. The repulsion does not change it.

Aili Ye 4L

I may be wrong, but we do not need to know any formulas. The angles we give should be approximate.

Aili Ye 4L

The positive charge on the nucleus attracts the extra electrons in the double and triple bonds thus causing a stronger bond.

Aili Ye 4L

The positive nucleus exerts a force on the electrons involved in the triple bond, causing the bond to be stronger and the electrons to be closer to the nucleus, meaning a shorter bond.

Aili Ye 4L

There is an electronegativity difference between the H and Cl atoms. Cl is more electronegative and thus attracts electrons more, causing the dipole.

Aili Ye 4L

Chemical bonds form when valence electrons of atoms interact. The type of bond that forms depends on electronegativity.

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The more positive charge for the same negative charge on isoelectronic atoms, the stronger the attraction and thus the smaller the radius.

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Ionization energy is the amount of energy required to remove the most loosely bound electron from a neutral atom in the gaseous state, whereas electronegativity is the measure of the tendency of an atom to attract a bonding pair of electrons. Ionization energy increases across a period (more protons...

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Electron affinity is the energy released when an electron is added to a neutral atom in the gaseous state. Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.

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Metals on the left tend to lose electrons, non-metals on the right tend to gain electrons, both try to reach the number of electrons of their closest noble gas.

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Argon is the noble gas that comes before Copper, and using its electron configuration we can avoid writing out copper's entire electron configuration. It helps us avoid writing lengthy and often distracting long configurations.

Aili Ye 4L

Do we need to memorize Rydberg's constant for test 2 or will the value be given?

Aili Ye 4L

You might have to find the work function, but then the other variables should either be given or can be found, and then work function should be easy to find with the equation.

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All objects have particle and wave properties. Electrons have measurable wavelengths because they have a small mass and the De Broglie wavelength is measured by Plank's constant divided by the mass times velocity. Larger objects have larger masses and thus their wavelengths are very difficult to mea...

Aili Ye 4L

As the person stated above, h-bar is the same thing as h/2, there is no difference.

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Some elements exist as diatomic elements since in their original state, their valence shells are not filled, thus they share electrons between each other and thus fill their shells and achieve a state of lower energy.

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Molarity's importance lies in how it defines the concentration of the solution and acting as a measurement of moles of solute per liter of solution. It is a big part of dilution calculations since moles of solute stay the same, so it is easy to calculate the molarity when knowing how much solution w...

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A mole of H₂ would include 6.02x10²³ molecules of H₂. But that would mean twice that for number of atoms.

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