CHEMISTRY COMMUNITY

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Cp is the heat capacity at constant pressure. Cv is the heat capacity at constant volume. According to PV = nRT, if temperature is changing, that means one other variable also has to change and this could be number of moles, pressure, or volume. It is important to know which ones are constant when c...

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w is given in joules. Some problems may represent it as kJ so it is important to pay attention.

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Yes, they would be referring to a constant external pressure.

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The reaction is transferring heat to its surroundings, so the system itself is losing heat. Therefore, it will have a negative value.

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Delta S = q / t. An insulated system has no change in temperature, so the value of T in the denominator is not going to change. However, even though the initial and final temperatures of the system are the same, it would change throughout the progress of the reaction. Therefore, there can still be h...

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Vibrational activity would have more degeneracy than nonvibrational activity, so Sc>Sb. Monatomic gases have more degeneracy than diatomic gases because there are more possible states for them to exist in. Therefore, the final answer is Sb < Sc < Sa.

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If you are not given a specific heat, you can use the generic formula for a gas. It depends on both the shape and conditions of the molecules observed. For an ideal gas in atomic form, Cv = (3/2)R and Cp = (5/2)R.

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R is the gas constant and C is a heat capacity.

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In general, if delta G is negative, then the reaction is spontaneous. Simply knowing change in entropy or heat does not directly tell you if a reaction is spontaneous or not.

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At a higher temperature, entropy is already higher than it would be at a lower temperature. As a result, the change in entropy will be lower.

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Q represents the current state of the system but K is the equilibrium state. Eventually, Q will go towards K.

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A buffer is a solution that resists changes in pH and it’s made by mixing a weak acid/base with its conjugate.

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If delta H is negative, it is exothermic. If delta H is positive, it is endothermic.

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You include all aqueous solutions and gases in the K expression.

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You use an ICE table to observe how concentrations change at equilibrium.

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You use the combined gas law to convert from liters of gas to moles.

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Remove products from the reaction so Q is less than K.

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It is when a molecule transfers a proton to another one of the same molecule.

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If the change in pressure changed the volume, it affects the concentration. If the change in pressure was caused by the addition of an intert gas, the volume hasn't changed so the concentrations have not changed.

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You omit the -x term when the equilibrium constant is very small (less than 10^3) because those changes are too small to have a significant effect on the concentration of reactants.

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C is asking about the equilibrium constant, which is a fixed value. D is asking about equilibrium concentrations, which depend on the initial reactions.

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The value of K would depend on whether pressure would change from a change in volume (would change) or addition of an inert gas (no change) based on how concentration would change.

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Set up and ICE table with initial, change, and equilibrium and use x to represent an unknown change.

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Le Chatlier's Principle states that if a system is disturbed, it will counteract the disturbance.

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Kc uses concentration while K uses partial pressure.

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Q would be greater than K if there are too many products. An external change could cause the system to have Q greater than K.

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Bronsted can accept or donate protons. Conjugate Avis is the conjugate of a base.

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They would have multiple H or OH.

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You need to know whether they are neutral, acidic, or basic.

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Cobalt is the coordinating metal in the middle.

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The number of dog figs starts after the decimal place for pH. So, if there are two dig figs you would use 2.46.

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A strong base completely dissociates in water and there are only a few. A weak base does not completely dissociate in water.

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The reaction between an acid and base is a neutralization reaction. The products of this reaction are a salt and water.

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A bronsted acid donates protons while a bronsted base accepts protons.

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A triple bond would have 1 sigma bond and 2 pi bonds.

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The shape of a coordination compound that has 3 ligands is trigonal planar.

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Bent has lone pairs while linear does not.

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Dispersion occurs between two nonpolar atoms/molecules. Hydrogen bonding occurs when an H is bonded to a highly electronegative atom.

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Sigma bond is the first bond that is formed and it the overlapping of two orbitals. Pi bonds are all the remaining bonds and they are formed by side by side orbitals.

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Each atom is hybridized based on the number of electron domains it has.

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Yes, all transition metals can form coordinate compounds.

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The shorter the bond, the stronger it is.

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Hybridization is when 2 or more orbitals combine. For example, if a carbon has 4 bonds, all 4 of those bonds are the same. All the electrons cannot be in the same orbital, so in order for them to be equal, the orbitals have to hybridize.

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The molecular shape names of the electron domains have roots that you can memorize. Then, try to memorize how you remove electrons to figure out the ones where there are lone pairs.

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Oxygen can have triple bonds, but it is usually most stable with two.

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Larger molecules are more polarizable than smaller ones, so the general trend is decreases across the row and increases down the column. Anions are more polarizable than cations because they are larger.

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No, neon gases are not included in the electronegativity trend, so neon is not more electronegative than fluorine.

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Larger size means larger bond length.

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A dipole-dipole force occurs when both compounds naturally have dipoles (HI). Induced dipoles occur when both molecules don't have a dipoles, and the induced dipole is caused by a random shift in the electron cloud.

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Hydrogen bonding and the polarity of the water molecule allow ionic substances to dissolve in water.

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A liquid has high viscosity when it has strong intermolecular forces so it tends to by sticky and slow-moving.

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You would have to follow the electronegativity trend. You would have to look at the electronegativity difference of O and S, not S and C. O is more electronegative than S, so there would be a greater difference between O and C compared to S and C, so CO2 would be more ionic than CS2.

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You can use the electronegativity difference between the two atoms to determine whether it has more ionic or covalent character. If the difference is greater than 1.5, it is ionic. If it is between 0.5 and 1.5, it is polar covalent. If it is less than 0.5, it is nonpolar covalent.

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In an ionic solid, there is an anion with a negative charge and a cation with a positive charge. The electrostatic attraction between the charged ions holds the solid together.

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NO2- has 18 electrons. Since 18 is an even number, there aren't going to be any unpaired electrons, so it would not be a radical. NO2 on the other hand would have an unpaired electron, so it would be a radical.

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The dual nature of light refers to its properties as a wave and particle. Formulas like c = λv are based of light's wave-like properties. The E = hv formula treats light as quantized photons.

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There was a discrepancy in these numbers because C-C bonds have resonance. So, they are partial single/double bonds.

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You look at the number of electrons in the outermost shell. This is the number of valence electrons.

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When drawing a bond, both dots and lines are synonymous. Lines are usually clearer in depicting the bonds. Unbonded electrons are always shown as dots.

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Electron shielding refers to the blocking of valence shell electron attraction by the nucleus due to the presence of inner-shell electrons. Penetration describes the proximity to which an electron can approach to the nucleus. The principal quantum number gives you an idea of how close the electron i...

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You need to look at the number of protons and effective nuclear charge to determine the order.

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You put the last noble gas configuration in brackets and then continue using spdf normally after that.

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The Balmer series is when the electron falls to the n = 2 energy level. The Lyman series is when the electron falls to the n = 1 energy level.

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E = hv calculates the energy of an individual photon.
E = 1/2mv^2 calculates the kinetic energy of a particle. Since photons have no mass, this equation is not applicable.

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The Heisenberg equation states that the product of the uncertainty in momentum times the uncertainty in position has to be greater than or equal to h/4π. This means there is a minimum number of uncertainty at all times.

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The standard unit for wavelength is m, and this is the output of equations relating to light. However, nanometers (10^-9) are also a common unit of measurement.

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An electron jumps to a higher energy state when it absorbs energy. It falls back to its original state when it emits that energy.

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The energy transition from n=5 to n=1 requires more energy than the energy transition from n=4 to n=2. More energy means shorter wavelength (E=hv), so the electron going from n=5 to n=1 would emit more energy.

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The wave nature of electrons affects the electron's energy levels. Electrons form standing waves and each energy level has to have a whole number of wavelengths for the standing wave to exist. So, the wave property of electrons dictates how there are fixed energy levels for each electron.

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Use the formula E=hv. We know that h is planck's constant (6.626*10^-34 m^2kg/s) and that v is frequency (1.09 x 10^15 s-1). If we plug these into the equation, we get E = (6.626*10^-34) (1.09 x 10^15) = 7.22 x 10^-19 J. Using the minimum frequency will also give the minimum amount of energy.

aishwarya_atmakuri

Use the number of significant digits given to you in the problem. Make sure you round your answer at the end to avoid losing precision.

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Round at the end of your calculation so you don't loose precision.

aishwarya_atmakuri

I believe he wanted you to focus on the reactants for the purpose of finding the limiting reactant.

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I would use the same number of significant figures as what is given in the problem.

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The best thing you can do is to review problems that focus on fundamentals. Make sure you check your answers and try to figure out what you can improve on!

aishwarya_atmakuri

When converting to atoms or molecules from moles, you need to use Avogadro's number. If you use with molar mass, Avogadro's number will give you the number of molecules. You know how many atoms are in each molecule, so then you can find the total number of atoms.

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