CHEMISTRY COMMUNITY

Tatiana Hage 2E

Enzymes tend to be homogeneous catalysts because they're usually in the same phase as the molecule it reacts with, to speed up the decomposition of a molecule.

Tatiana Hage 2E

A reactant is consumed by the reaction, and a catalyst is not.

Tatiana Hage 2E

Absorption is the process in which a fluid is dissolved by a liquid or a solid. Adsorption is the process in which atoms, ions or molecules from a substance (gas, liquid or dissolved solid) adhere to a surface of the adsorbent. Adsorption can be used to separate out unwanted substances.

Tatiana Hage 2E

They are separated by a comma because they are in the same phase (gas).

Tatiana Hage 2E

Platinum is an inert conductor that is added to the half reaction that has no conducting solids. You place a line if the elements are in different phases, and a comma if they are in the same phase.

Tatiana Hage 2E

Yes I believe so.

Tatiana Hage 2E

An elementary reaction is a chemical reaction in which one or more chemical species react directly to form products in a single reaction step and with a single transition state.

Tatiana Hage 2E

A unique rate is a rate of appearance/disappearance of any of the species in a reaction divided by its stoichiometric coefficient; when average rate is calculated, the coefficient is not taken into account.

Tatiana Hage 2E

There is a negative sign because the concentration of the reactant decreases during the reaction.

Tatiana Hage 2E

Also, inert electrodes like platinum do not participate in the redox reaction and are present so that current can flow through the cell.

Tatiana Hage 2E

If the standard potential is positive, ∆G is negative and the reaction has a spontaneous tendency to form products.
If the standard potential is negative, ∆G is positive and the reverse of the cell reaction is spontaneous, so the cell reaction has a spontaneous tendency to form reactants.

Tatiana Hage 2E

We use the initial rate because it is the fastest rate and the only time that we know the concentrations of the reactants, since the rate decreases as the reactants are used up.

Tatiana Hage 2E

It would be the same as ΔS_sys of part a, the isothermal and reversible process. ΔS_surr = 0 for free expansion so ΔS_tot = ΔS_sys.

Tatiana Hage 2E

Work = 0 in free expansion because there is no external pressure applied, so P=0 and therefore w=0. Since ΔU = 0, that means that q=0 as well, so no heat is transferred into the surroundings.

Tatiana Hage 2E

At equilibrium, ΔS_sys = - ΔS_surr.
Also, ΔG = 0 for a reaction at equilibrium.

Tatiana Hage 2E

Gibbs free energy is defined as the maximum useful work (excluding work associated with volume changes of the system) that a system can do on the surroundings when the process occurs reversibly at constant temperature and pressure.

Tatiana Hage 2E

W = the number of microstates^{number of particles in the system}

Tatiana Hage 2E

G is defined as the maximum non-expansion work under constant temperature and pressure. Since work done by the system is negative, deltaG < w, so deltaG is the maximum work that may be done.

Tatiana Hage 2E

The textbook says the first law of thermodynamics is that the internal energy of an isolated system is constant, so I think that would be sufficient.

Tatiana Hage 2E

Liquids have a higher heat capacity than gases or solids so their slope is going to be less steep.

Tatiana Hage 2E

The temperature stays constant in an isothermal process. For an ideal gas, in an isothermal process, ΔU = 0 = Q − W, so Q = W.

Tatiana Hage 2E

The standard enthalpy change of formation of a compound is the enthalpy change which occurs when one mole of the compound is formed from its elements under standard conditions, and with everything in its standard state. However, the standard enthalpy change of a reaction is the enthalpy change which...

Tatiana Hage 2E

Yes because no matter or energy can be exchanged with the surroundings.

Tatiana Hage 2E

There's a link on the class website called Constants and Equations where you can find the formulas.

Tatiana Hage 2E

If the matter cannot be transferred through the boundary but energy can be exchanged with the surroundings, then that is a closed system. For an isolated system, neither energy nor matter can be exchanged with the surroundings.

Tatiana Hage 2E

A reversible isothermal expansion is an increase in volume at constant temperature. A reversible reaction does more work because all heat is converted to work.

Tatiana Hage 2E

Hess's Law states that the overall reaction enthalpy is the sum of the reaction enthalpies of the steps into which the reaction can be divided. To use Hess's Law to find the enthalpy of a given reaction, we find a sequence of reactions with known reaction enthalpies that adds up to the reaction of i...

Tatiana Hage 2E

Heat is dependent on the path or the way the state of the system changes.

Tatiana Hage 2E

Enthalpy is a state function because it depends only on the state of the system and not on the path taken to reach its value.

Tatiana Hage 2E

Melting only requires enough energy for the molecules to escape from their sites in the solid, but for vaporization, you need enough energy to be able to break most of the intermolecular attractions.

Tatiana Hage 2E

Bronsted definition: an acid is a proton (H+ ion) donor, and a base is a proton acceptor.
Lewis definition: an acid is an electron acceptor, and a base is an electron donor.

Tatiana Hage 2E

Hope this picture helps!

Tatiana Hage 2E

The seesaw shape occurs when a molecule has a central atom bonded to 4 other atoms and 1 lone pair.

Tatiana Hage 2E

The roman numerals indicate the oxidation state of the metal in the complex.

Tatiana Hage 2E

Oxygen is less electronegative, so it is more likely to share its valence electrons than Fluorine, which is very electronegative.

Tatiana Hage 2E

Bond orders can give you an indication of the stability of a bond. A high bond order indicates more attraction between electrons, so the atoms are held together more tightly. With a lower bond order, there is less attraction between electrons so the atoms are held together more loosely. The higher t...

Tatiana Hage 2E

I think you are correct, because that Lewis structure gives both atoms a formal charge of 0.

Tatiana Hage 2E

Yes, an atom with a lone-pair of electrons can be a Lewis base because it donates its electron pair to a Lewis acid.

Tatiana Hage 2E

It also helps to check the formal charges of each atom. For example, with HOCO, placing the unpaired electron on the carbon gives it a formal charge of 0.

Tatiana Hage 2E

The formation of an ionic bond is the result of the transfer of one or more electrons from a metal onto a non-metal. Polar bonding is the unequal sharing of electrons between two different non-metal atoms. Nonpolar covalent bonds, with equal sharing of the bond electrons, arise when the electronegat...

Tatiana Hage 2E

The electron configuration for electrons at the ground state will be at the lowest energy state possible for that atom.

Tatiana Hage 2E

Cu is the other unique element. A completely full or half full d sub-level is more stable than a partially filled d sub-level, so an electron from the 4s orbital is excited and rises to a 3d orbital. Their electron configurations are - Cr: [Ar] 3d⁵4s¹ and Cu: [Ar]3d¹⁰4s¹

Tatiana Hage 2E

For chromium and copper, a completely full or half full d sub-level is more stable than a partially filled d sub-level, so an electron from the 4s orbital is excited and rises to a 3d orbital.

Tatiana Hage 2E

n(initial)-n(final) gives me a negative frequency. Is this right? You should get a negative number because you are going from a higher energy state to a lower energy state. Quantitatively, you would be subtracting a not as negative number from a negative number. The negative result from this indica...

Tatiana Hage 2E

This link might help explain it: http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch6/quantum.html "Because they have opposite electrical charges, electrons are attracted to the nucleus of the atom. Energy must therefore be absorbed to excite an electron from an orbital in which the electro...

Tatiana Hage 2E

n(initial)-n(final) gives me a negative frequency. Is this right?

Tatiana Hage 2E

For tests, should we know that 486 nm represents blue light, 700 nm is red, and so on?

Tatiana Hage 2E

I solved the problem and got 150 pm as well, which is the answer given in the solutions manual.

Tatiana Hage 2E

Hz is 1 cycle per second, so it is always interchangeable with s^-1

Tatiana Hage 2E

You would know when there are no limiting reactants in an equation if both reactants produced the same mass of a product.

Tatiana Hage 2E

There are 2 sig figs in 0.053 since the 0's before 53 do not count.

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