CHEMISTRY COMMUNITY

Marni Kahn 1A

when writing a pseudo rate law, why is the rate constant k denoted as k'(k prime)?

Marni Kahn 1A

how can you tell the difference between a catalyst and an intermediate molecule when looking at elementary reactions?

Marni Kahn 1A

What is a catalytic converter and when is it used?

Marni Kahn 1A

Are we responsible for knowing how to calculate A, or will the value be given to us?

Marni Kahn 1A

Why can Activation energy(Ea) replace change in enthalpy(delta H) in the van't hoff equation?

Marni Kahn 1A

Yes galvanic cells are always spontaneous and produce an electric current

Marni Kahn 1A

Yes both are okay but it is important not to get them mixed up because they equate to different values.

Marni Kahn 1A

Yes I think that minimum potential means the Standard E cell

Marni Kahn 1A

what is meant by a rate law?

Marni Kahn 1A

do we have to know the graph of [A] vs time or just ln[A] vs time for the first order rate law and integrated rate law?

Marni Kahn 1A

You include Pt when there is no other ironically conducting solid to transport electrons. Pt as a solid is included on either end of the cell diagram, as solids are typically on the end of the cell diagrams.

Marni Kahn 1A

Whereas galvanic cells produce a current as a result of spontaneous reactions taking place, electrolytic cells require a current to initiate a non spontaneous reaction. Batteries are galvanic cells since the voltage produced is produced without any additional current required

Marni Kahn 1A

You add electrons to the reactant side of reduction reactions because that substance is gaining electrons. Conversely, you add electrons to the product side of oxidation reactions since that substance is losing electrons.

Marni Kahn 1A

I don’t believe it matters, as long as there is a comma separating the two solutions.

Marni Kahn 1A

If it is a galvanic cell, you flip the equation that will render you a positive Ecell value.

Marni Kahn 1A

K is in terms of pressure, whereas Kc is in terms of concentration/molarity.

Marni Kahn 1A

it demonstrates how K depends on temperature when combined with the gibb's free energy equation Δ G = Δ H − T Δ S

Marni Kahn 1A

You can break down the equation you are given into two different equations to determine how the charges on the molecules change.

Marni Kahn 1A

You have the natural log in the equation already given ∆G=∆G°+RTlnQ, and then ∆G°=-RTlnK at equilibrium(∆G=0 at equilibrium)

Marni Kahn 1A

∆G is the change of Gibbs (free) energy for a system and ∆G° is the Gibbs energy change for a system under standard conditions (1 atm, 298K)

Marni Kahn 1A

Do we use the equation U(total)=(3/2)nrt when the reaction of the system is isothermal?

Marni Kahn 1A

I typically draw out all of the compounds in the reaction and then observe which bonds must break in order to form those on the products side.

Marni Kahn 1A

Why do larger, more complex molecules possess larger standard entropies than simpler, smaller molecules in the same phase?

Marni Kahn 1A

Is Gibbs Free Energy a state property, and if so why?

Marni Kahn 1A

In what cases does delta S(total)=0?

Marni Kahn 1A

is there such thing as a negative entropy value? if so, what does this mean?

Marni Kahn 1A

is the equation U(total)=(3/2)n*R*T only used when there has been an isothermal reversible expansion reaction?

Marni Kahn 1A

is the equation delta S=n*R*ln(v2/v1) only used when there has been an isothermal, reversible expansion reaction?

Marni Kahn 1A

why is a car engine considered an open system?

Marni Kahn 1A

why is a reaction in a bomb calorimeter considered an isolated system?

Marni Kahn 1A

why is a sealed beaker of water considered a closed system?

Marni Kahn 1A

It is also important to take into consideration that some reactions require a change in enthalpy due to a phase change in addition to the substances' bond enthalpies. In this way, Hess's method is more efficient and not as time costly because the enthalpy changes are already given.

Marni Kahn 1A

Why is the standard enthalpy of formation of Carbon in the form of graphite equal to 0?

Marni Kahn 1A

When do we use bomb calorimeters? When the gas is at constant pressure or volume and why?

Marni Kahn 1A

Does there need to be a conversion done to go from kJ/Celcius to kJ/Kelvin?

Marni Kahn 1A

Why is specific heat capacity an intensive property, but heat capacity is an extensive property?

Marni Kahn 1A

Why do exothermic reactions render negative values for delta H, and endothermic reactions render positive values for delta H?

Marni Kahn 1A

why does the temperature of a sample remain constant even though heat is being supplied during melting/boiling?

Marni Kahn 1A

why is enthalpy a state property?

Marni Kahn 1A

This is seen quite often because we do a lot of examples with an infinitesimally small value of Ka

Marni Kahn 1A

why does steam cause severe burns?

Marni Kahn 1A

What does a high percentage deprotonation indicate? What does a high percentage protonation indicate?

Marni Kahn 1A

Are there any other examples besides H20 that demonstrates autoprolysis (one molecule transfers a proton to another molecule of the same kind) and are significant?

Marni Kahn 1A

The higher the Kb value, the more basic a substance is. The higher the Ka value, the more acidic a substance is.

Marni Kahn 1A

ALegala_2I wrote:Why do changes in concentration, pressure, and volume have no effect on the K value?

The constant K is temperature-dependent, meaning that only changes in temperature will affect the value of K.

Marni Kahn 1A

The pKa and pKb values indicate the strength of acids and bases. The lower the pKa value, the stronger the acid. The lower the pKb value, the stronger the base.

Marni Kahn 1A

K is also important because if given K and initial concentrations of one or more reactants, you can use that K value to find the composition of the mixture at equilibrium.

Marni Kahn 1A

An important thing to consider when there is a change in pressure is how the pressure has changed. If it has changed by adding an inert gas, then the equilibrium is unaffected. However, if there is a change in pressure by adjusting the volume, then see how that change in volume affects the concentra...

Marni Kahn 1A

The reaction rates are equal at equilibrium, which makes the concentrations of reactants and products constant.

Marni Kahn 1A

assume K and Q are measured in units used for gasses, unless it is specified to calculate Kc or Qc values which use mol/liter

Marni Kahn 1A

I think that you were getting confused with aqueous solutions, which are included in K calculations

Marni Kahn 1A

When finding the composition of an equilibrium mixture, what do you do if the equation becomes a cubic instead of a quadratic?

Marni Kahn 1A

What is the difference between homogenous and heterogenous equilibria?

Marni Kahn 1A

When a mixture is compressed, causing the volume to decrease, and there are more moles of gas on the reactant side of the equilibrium equation, which way does the equation shift and why?

Marni Kahn 1A

What happens when Q>K, Q<K, and Q=K, and why?

Marni Kahn 1A

solids and liquids are not included in the "ICE" box calculations.

Marni Kahn 1A

Organic molecules contain both hydrogen and oxygen

Marni Kahn 1A

The textbook says that every Bronsted base is a lewis base, because if a molecule is accepting an H+ then it is also donating e- to fill the H+ empty shell

Marni Kahn 1A

Why does an acid get protonated when the pH of its solution is greater than the pka of the acid?

Marni Kahn 1A

Why are cations from groups 1 and 2 considered too weak to form acidic solutions?

Marni Kahn 1A

What does the Pka tell us that the pka doesn't?

Marni Kahn 1A

Are we responsible for memorizing the amphoteric compounds shown to us in class, or should we just understand their importance?

Marni Kahn 1A

Are all lewis acids/bases considered to be Bronsted acids/bases? Are all Bronsted acids/bases considered to be Lewis acids/bases?

Marni Kahn 1A

Are we responsible for knowing how to calculate K(a), or just knowing its significance?

Marni Kahn 1A

Are polyprotic acids/bases necessarily stronger than monoprotic acids/bases?

Marni Kahn 1A

is there a difference between chlorido and chloro, florido and fluoro, or cyanido and cyano?

Marni Kahn 1A

are there any instances where f-orbitals are hybridized or do we not have to know that?

Marni Kahn 1A

can lone pairs on the central atom be hybridized?

Marni Kahn 1A

can any other atoms besides Carbon atoms be "promoted" to increase bond formation?

Marni Kahn 1A

why do pi bonds inhibit rotation of a molecule?

Marni Kahn 1A

why aren't p-orbitals hybridized?

Marni Kahn 1A

I know that when the central atom has only two bonding pairs as far as possible, forming an 180 degree angle, it is considered to be a linear shape, but what if the central atom has lone pairs in addition to the two bonds?

Marni Kahn 1A

Does it matter which resonance structure we use when studying the VSEPR model?

Marni Kahn 1A

Why does SF6 have an octahedral shape?

Marni Kahn 1A

How are all of the bond angles of Methane, CH4, 109.5 degrees?

Marni Kahn 1A

Why does every molecule possess the induced dipole-induced dipole force?

Marni Kahn 1A

Are hydrogen bonds or dipole-dipole attractions stronger and why?

Marni Kahn 1A

Why do the boiling points increase down group 17 when the atoms are bonded to a Hydrogen atom?

Marni Kahn 1A

How long does an instantaneous dipole moment typically last?

Marni Kahn 1A

Why does the strength of a dispersion force depend on the polarizability of the atoms in a molecule?

Marni Kahn 1A

Are London interactions between rod-shaped molecules stronger than london interactions between spherical molecules and if so, why?

Marni Kahn 1A

Are we responsible for knowing how to calculate the partial charge of an atom in a molecule?

Marni Kahn 1A

What does it mean when elements have a high polarizability?

Marni Kahn 1A

Why do london forces cause boiling points of molecules to increase down a group?

Marni Kahn 1A

Do London Interactions increase or decrease down a group and why?

Marni Kahn 1A

PCl5 (phosphorus pentachloride), since P has 10 valence electrons

Marni Kahn 1A

Which bond (single, double, triple) is the most stable and why?

Marni Kahn 1A

What exactly is electronegativity and why does it increase across a period from left to right?

Marni Kahn 1A

Do d block elements tend to gain or lose electrons to have the configuration of a noble gas?

Marni Kahn 1A

Why are Helium, Lithium, Beryllium, and Hydrogen exceptions to the lewis dot structure in terms of creating an octet for each atom

Marni Kahn 1A

Why does the element with the lowest IE go in the middle when drawing Lewis Dot structures?

Marni Kahn 1A

Why do atomic radii generally decrease from left to right across a period if the atomic number is increasing(# of electrons/protons)?

Marni Kahn 1A

Why do ionic radii generally increase down a group?

Marni Kahn 1A

Does it matter the order in which we assign the m values(l,l-1...-l) to the orbitals of a subshell?

Marni Kahn 1A

Does the d orbital of an n=4 shell have a higher energy level than the p orbital of an n=5 even though it is filled before the p orbital?

Marni Kahn 1A

The x is an arbitrarily assigned variable that represents the value of m

Marni Kahn 1A

What did the double-slit/diffraction experiment prove, and with what equations can we associate the experiment?

Marni Kahn 1A

Why is momentum involved in the debrogile equation if the mass of a particle is so tiny and isn't that significant?

Marni Kahn 1A

Do we need to be familiar with the Balmer and Lyman series in terms of which energy levels are associated with n1, and in what type of light they occur?

Marni Kahn 1A

Why does the ionization energy generally increase across a period from left to right?

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