CHEMISTRY COMMUNITY

Annalise Eder 2L

Transition states have partial bonds and are not defined as individual molecules.

Annalise Eder 2L

Using the steady step method will get you the same result as using the pre-equilibrium approach. Either way you will need to identify the slow step of the reaction as it is the rate determining step.

Annalise Eder 2L

A catalyst provides an alternate pathway and that pathway has a lower activation energy than the original. It increases the number of successful collisions.

Annalise Eder 2L

What do chemists call a benzene ring with iron atoms replacing the carbon atoms?

A ferrous wheel.

Annalise Eder 2L

More complex molecules generally have high heat capacities because they have more degrees of freedom and more ways to store energy. Materials with more atoms per unit volume will generally have higher heat capacities.

Annalise Eder 2L

The pre-equilibrium approach should be used on problems where the slow step is not the first step in the reaction and the reaction rate of the later step contains and intermediate. You could also try using the steady state approach, but this is much more complicated and difficult.

Annalise Eder 2L

A photon checks into a hotel and is asked if he needs any help with his luggage. He says, "No, I'm traveling light."

Annalise Eder 2L

The integrated rate law for a first order reaction is ln[A]=ln[A]initial-kt. I am unsure what the other equation is that you are referring to.

Annalise Eder 2L

The variable for a second order reaction that create a linear graph are 1/[A] over time while for a first order reaction it is ln[A] over time and for a zero order reaction it is [A] over time. The 1/[A] creates a positive slope because as the concentration of A decreases 1/[A] increases.

Annalise Eder 2L

If you're not part of the solution, you're part of the precipitate.

Annalise Eder 2L

You will want to balance the equation with the solid metal on the reactants side and the aqueous dissociated ions on the product side. If the formation of the ions is favorable, the metal will dissolve in the solution.

Annalise Eder 2L

The rate constant k, associated with kinetics, is related to the activation energy required for a reaction to occur and can tell you about the speed of a reaction and how quickly is reaches equilibrium. Thermodynamics is related to the free energy, ΔG, given off by a reaction and tells you about a r...

Annalise Eder 2L

Don't forget to include phases for all of the elements. The Br ions would be (aq).

Annalise Eder 2L

An electrochemical series is a list of reduction half reactions listed in order of increasing E°values.

Annalise Eder 2L

For acidic questions balance with H3O+ and water. For basic conditions use OH- and water.

Annalise Eder 2L

Gibbs free energy is an extensive property that depends on the amount and concentration of substances.

Annalise Eder 2L

If you were to leave the + off of your answer on a test I am sure you would get full credit.

Annalise Eder 2L

Reduction and oxidation occur together. This is why they are called redox reactions.

Annalise Eder 2L

This is an open system because it can freely exchange energy and matter with its surroundings.

Annalise Eder 2L

Heat is a measure of thermal energy being transferred and does not necessarily result in a change of temperature.

Annalise Eder 2L

Heat capacity is an extensive property and therefore depends on the amount of a substance. Specific heat capacities of elements are different depending on what state they are in. Therefore, it is difficult to measure the periodic trends.

Annalise Eder 2L

The heat capacity equation is Q = ncΔ T
Change in entropy can be calculated using different equations depending on the situation
Boltzmann' equation: S = kB ln W
for an isothermal process ∆S = qREV/T
for a reversible process: ∆S = nR lnV2/V1
at constant volume: ∆ST1 ---> T2= nC ln(T2/T1)

Annalise Eder 2L

Both have to do with a transfer of energy. Work is defined as the amount of energy transferred by a force acting through a distance. Heat is defined as the energy stored as random motion of molecules or atoms.

Annalise Eder 2L

In an adiabatic system there is no transfer of heat while in an isolated system there is no contact with the surroundings and therefore no exchange of energy or matter.

Annalise Eder 2L

For enthalpy, delta H, pressure is constant. For change in internal energy, delta U, volume is constant.

Annalise Eder 2L

These numbers have to do with the equipartition of energy theorem which involves molecules' degrees of freedom. It depends on translational and rotational degrees of freedom. R is the gas constant.

Annalise Eder 2L

On the other hand, path functions do depend on the path taken from initial to final state. One way to think about state functions is if you had a bank account with $1,000 in it and you took out $100 at once or $25 on four separate occasions, you would have $900 left in your bank account either way a...

Annalise Eder 2L

Enthalpy is a state function meaning it does not matter what path was taken. It depends only on the initial and final states. Enthalpy requires constant pressure and measures the heat given off or taken up by a reaction. On the other hand, heat is a path function meaning it does depend on the path t...

Annalise Eder 2L

This relates to calorimetry because heat capacity is an extensive property that depends on the amount of the substance while specific heat is an intensive property that does not change based on the amount of the substance.

Annalise Eder 2L

The reaction enthalpy is the heat taken up or given off during a reaction which is the difference in enthalpies between the products and the reactants. The enthalpy of formation is the change in enthalpy between elements in their standard states to the compound they form.

Annalise Eder 2L

pH tells you the concentration of hydronium while pKa tells you the substance's ability to give up protons. For both, a lower number means a stronger acid. However, the pH scale is not the same as pKa values. If a substance has a Pka value over 7 it does not mean it is a base.

Annalise Eder 2L

HCOOH is a slightly stronger acid than CH3COOH because H is slightly more electronegative than the CH3 group. A stronger acid forms a more stable anion when it dissociates and HCOO is more stable than CH3COO.

Annalise Eder 2L

The definition of a Lewis acid is a substance than can accept a pair of electrons while a Lewis base is a substance that donates a pair of electrons. Cations, atoms with an incomplete octet, or molecules where the central atom can have an expanded octet can act as Lewis acids. An atom, ion, or molec...

Annalise Eder 2L

You use the least electronegative atom as the central atom. Nitrogen is less electronegative than oxygen.

Annalise Eder 2L

A single bond is always a sigma bond. In a a double or triple bond the first bond is always a sigma bond, but any following bonds must be pi bonds.

Annalise Eder 2L

You can determine the bond angle based on the hybridization. SP has 180 degree bond angle, SP2 has 120 degree bond angle, and SP3 has 109.5 degree bond angle usually. As the number of p orbitals increases the s character decreases as does the bond angle as seen with the given numbers.

Annalise Eder 2L

If all of the species given are gases then partial pressure can be used to calculate the equilibrium constant. If you are given Kp you would also use partial pressure. If you are given Kc you would use concentration.

Annalise Eder 2L

Copper is also an exception because its electron configuration is [Ar]3d10 4s1 not [Ar] 3d9 4s2. This is because a half-filled or full d subshell is more stable.

Annalise Eder 2L

You always remove electrons from the outmost shell first. This is because the electrons in front of them are essentially blocking them from the pull of the nucleus.

Annalise Eder 2L

Hydrogen does not take a full octet. It has a half filled 1s orbital and only wants one more electron. Therefore it has high electronegativity.

Annalise Eder 2L

Knowing the series may also be helpful. The Balmer series is associated with energy changes where n=2 and exists in the visible light spectrum. The Lyman series is associated with energy changes where n=1and exists in the UV spectrum. These series are for Hydrogen only.

Annalise Eder 2L

The electron affinities are close to zero. Noble gases have complete octets and do not want any more electrons. The Alkaline metals also have very low electron affinity as they often form cations and prefer to give up electrons than gain them.

Annalise Eder 2L

The quantum number n gives the energy level while the angular momentum quantum number tells you the subshell of the electron. So use n as l does not give you information about the energy level. For potassium and Calcium 4s has lower energy than 3d which may seem counterintuitive, but for Scandium th...

Annalise Eder 2L

The electrons in the 3d orbitals essentially shield electrons in the 4s orbital from the nucleus, so electrons in the 4s orbital are lost first during ionization.

Annalise Eder 2L

Sulfur can have an expanded octet by using the empty 3d orbitals to accommodate "extra" electrons.

Annalise Eder 2L

I would just choose the answer choice that best fits the question and repeat the calculations without worrying about them being included in the given answers.

Annalise Eder 2L

For Potassium and Calcium, 4s is lower in energy than 3d. From Scandium on 3d is lower in energy

Annalise Eder 2L

The wavelength of the emitted photon is 102.6 nm which is in the ultraviolet spectrum. This section of the emission spectra for Hydrogen is know as the Lyman series which always corresponds to n=1 as one of the principle energy levels.

Annalise Eder 2L

This equation is used to calculate the energy of a photon when you are given the wavelength of the light. For example, you could use this equation on homework question 1.9 where you are given the wavelength 2.5 nm and asked for the frequency and energy of the photon.

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