CHEMISTRY COMMUNITY

Amy Kumar 1I

Yes, Ka is the dissociation constant based on the H+ concentration and Kb is the dissociation constant based on the OH- concentration.

Amy Kumar 1I

Yes make sure the equation is balanced so that you can be sure that the exponents are correct and the same as the stoichiometric coefficients.

Amy Kumar 1I

deltaG* implies the standard conditions of 1 M concentration, 1 atm pressure, and 25 degrees Celsius.

Amy Kumar 1I

The value for work would be negative if the system was doing work on the surroundings.

Amy Kumar 1I

If the concentration and the rate are being changed by the same factor, then it is a first order reaction.

Amy Kumar 1I

Kaylee Clarke 1G wrote:what of the elements such as platinum that seem to be attached to a cell diagram?

Platinum is used because it is an inert electrode.

Amy Kumar 1I

What is a rate limiting step and how do we find it?

Amy Kumar 1I

How do you find K’ for multi step reactions?

Amy Kumar 1I

What are the ways/steps to determine the order of a reaction?

Amy Kumar 1I

Why does the rate for the reverse reaction use K’ instead of K?

Amy Kumar 1I

What is molecularity and it’s relation to rate laws?

Amy Kumar 1I

How is the n value in deltaG=-nFE(cell) calculated?

Amy Kumar 1I

Is the sign for standard energy potential switched for oxidation half reactions?

Amy Kumar 1I

Comma is used if there are multiple species in the same phase while a line is used to separate phases such as aqueous, gas, liquid, and solid.

Amy Kumar 1I

Keep the overall charge of the molecule in mind and use typical oxidation numbers such as -2 for oxygen and +1 for group 1A elements.

Amy Kumar 1I

Q is used at any point in the reaction when it is not at equilibrium.

Amy Kumar 1I

Use platinum since it is an inert electrode.

Amy Kumar 1I

Why cannot the electron transfer of one cell be measured?

Amy Kumar 1I

How are max cell potential and free energy difference between reactants and products related?

Amy Kumar 1I

Use typically known oxidation states (such as -2 for oxygen) and work backwards from the overall charge to find the oxidation state of the remaining element(s).

Amy Kumar 1I

What do you do when balancing redox reactions for alkaline solutions? How is it difference from acidic solutions?

Amy Kumar 1I

A single line represents separation of phases or a porous disk while a double line represents a salt bridge.

Amy Kumar 1I

In endothermic reactions, heat is like a reactant. This means that if heat is added, there are more reactants, which means that reaction will shift towards the products in the forward direction.

Amy Kumar 1I

The entropy of the system and surroundings added up equal the entropy of the surroundings. In cases where the entropy of the surroundings is 0, the entropy of the system equals -1*entropy of the surroundings.

Amy Kumar 1I

Use the given positive values for all the bond enthalpies and use the equation (bonds broken)-(bonds formed) to calculate the overall delta h.

Amy Kumar 1I

Make sure your units cancel out and the unit for pressure (bar, atm, Torr) matches the unit for the pressure value in the question.

Amy Kumar 1I

Reversible: w=-nRT(ln(v2/v1))
Irreversible: w=-p(delta v)

Amy Kumar 1I

I was just on this problem and luckily found this post. Are we supposed to know that 1atm is equivalent to 760 torr or is that somewhere on the equation sheet? Also how do we convert from L*atm to kJ? Both conversions are given on the constants and equations sheet. 1 L.atm = 101.325 J 1 atm = 760 t...

Amy Kumar 1I

Since strong acids dissociate completely, a Ka value is usually not given.

Amy Kumar 1I

What are the different situations in which delta U can equal 0?

Amy Kumar 1I

What is the setup for when the delta h rxn is given at a specific temperature but we are being asked to calculate the delta h rxn at another temperature?

Amy Kumar 1I

Since the q value in the delta s = q(rev)/T equation is the energy transferred reversibly as heat, is there a separate equation needed to find q for a reversible reaction (similar to how there is a different equation to find w if the reaction is reversible)?

Amy Kumar 1I

Yes, taking the reverse reaction allows the products and reactants to switch sides so that things can get canceled out as needed.

Amy Kumar 1I

The heat capacity for the calorimeter takes the mass and everything else into account already.

Amy Kumar 1I

What are the three ways to change the energy of a system?

Amy Kumar 1I

Why is P*delta V significant for changes in the number of moles of gas and insignificant for solids and liquids?

Amy Kumar 1I

What is the difference between the "small" and "large" errors in s and how does that influence whether a property is thermodynamic or statistical?

Amy Kumar 1I

Why do we not know if a reaction will occur just because the delta U value is negative?

Amy Kumar 1I

Also make sure to check if the the reactants and products are on their appropriate sides across all the equations before making changes to the equations.

Amy Kumar 1I

Are there any situations where you would not be able to simply "add" chemical reactions together to determine overall delta h?

Amy Kumar 1I

During lecture, there was a slide that mentioned that because heat is required during melting or boiling, the temperature of a sample remains constant even though heat is being added. Can someone please explain what this means?

Amy Kumar 1I

For the reaction Br2(l) --> 2Br(g), how do you know which phase change enthalpies to use (why is it delta h vap + delta h bond)?

Amy Kumar 1I

In the example that Dr. Lavelle used during lecture, drawing the Lewis structures reveals that the double bond between the carbons in ch2 is broken since the product (ch3ch2br) only has a single bond between the carbons. You would have to compare the Lewis structures of the reactants and the product...

Amy Kumar 1I

When is it a state function, you only need to take the initial and final states into consideration instead of all the intermediate pathways as well. This makes it easier to calculate change.

Amy Kumar 1I

Liquids (solvents) are usually in excess in the reaction, so they are not included because there is no significant change in their concentrations.

Amy Kumar 1I

The basic idea is that K values change based on the temperature.

Amy Kumar 1I

Why does adding heat to a reaction drive product formation?

Amy Kumar 1I

The R values are constant and change based on the units of pressure being used.

Amy Kumar 1I

Since values smaller than 10^-3 can typically allow the approximation method to be used, if the value is less than but somewhat close to 10^-3, you should definitely check to be sure.

Amy Kumar 1I

Just make sure the units are the same throughout, which means that the R value with the same unit is used in the equation.

Amy Kumar 1I

By rearranging the ideal gas equation, n/v can be isolated for which means that the concentration can be calculated for because n/v is the concentration/molarity.

Amy Kumar 1I

Since solids technically do not have a concentration, they are not involved in equilibrium constant equations. This means that equilibrium constants are the same even if the solid is removed.

Amy Kumar 1I

Stoichiometric coefficients are the exponents that show that there multiples quantities of the substance. In this case, the concentration values are raised to the power of the stoichiometric coefficients.

Amy Kumar 1I

Q is when the values used at the concentrations at a specific time, not the equilibrium values at concentration. Kc and Kp use the concentration values at equilibrium.

Amy Kumar 1I

why are amphiprotic always amphoteric but not the other way around?

Amy Kumar 1I

what are the reactions for some amphoteric compounds showing that they can act as acids and bases?

Amy Kumar 1I

how are lone pair shown in hybridization?

Amy Kumar 1I

why are pi bonds shown in the p orbital?

Amy Kumar 1I

If the shape is tetrahedral and all attachments are the same, dipoles cancel.

Amy Kumar 1I

Is nitro a mono, bi, or polydentate? Which element's lone pairs are considered?

Amy Kumar 1I

How do you determine if a ligand is polydentate?

Amy Kumar 1I

Can someone please explain the inductive effect in relation to delocalization.

Amy Kumar 1I

What happens when a metal oxide reacts with water? Is a base produced or does the metal oxide break down into a metal cation and hydroxide ions?

Amy Kumar 1I

Also, the anion is written before the neutral ligand.

Amy Kumar 1I

The extra orbital is needed for the 4th electron in an sp2 orbital, which can hold 3 electrons. The un-hybridized p electron is unpaired.

Amy Kumar 1I

Work backwards from the overall charge and charge of the ligands to find the charge on the metal.

Amy Kumar 1I

Can someone please example the porphyrin ligand-tetradentate example from lecture with relation to heme complexes?

Amy Kumar 1I

What is the biological benefit of transition metals having many oxidation states?

Amy Kumar 1I

When are bis-, tris-, tetrakis- used instead of di-, tri-, tetra-?

Amy Kumar 1I

Why are bound ligands a part of the coordination sphere?

Amy Kumar 1I

A bronsted acid is a chemical species that can donate a proton. An example is CH3COOH (acetic acid).

Amy Kumar 1I

Hybridization makes it easier to see the different types of bonds that are present. It is also meant to show that the "fusing" of orbitals affects shapes and ability to bond.

Amy Kumar 1I

Closer because radius is a variable in Coulomb's Law.

Amy Kumar 1I

How do we determine the different effects of axial and equatorial lone pairs on molecule shape?

Amy Kumar 1I

Are resonance structures considered when determining molecular shape?

Amy Kumar 1I

Is there formation of hydrogen bonds related in any way to polarity?

Amy Kumar 1I

Radicals count as 1 region of electron density but the repulsion is not as great as that of a lone pair.

Amy Kumar 1I

The cis molecule in the example during lecture was polar while the trans molecule was non-polar because the dipole moments canceled out.

Amy Kumar 1I

The half-filled orbitals for nitrogen and more stable and harder to remove an electron from than the 1 orbital in oxygen that has 2 paired electrons.

Amy Kumar 1I

You can use the general trends in increasing and decreasing electronegative for the periodic table can help identify the general differences in electronegativity between 2 elements without needing to know the exact values.

Amy Kumar 1I

By using (-hR/n^2) for the final n value minus (-hr/n^2) for the initial n value, you can find the energy difference. If the energy difference and one of the n values are known, you can rearrange the equation to find the other n value since -hR is a constant value.

Amy Kumar 1I

If you are given the mass of the reactants, convert it to moles of each reactant using the molar mass from the periodic table. Then divide each molar value by the smallest molar value and multiply to get whole numbers if necessary.

Amy Kumar 1I

For boron, not having an octet and having just 6 shared electrons makes it formal charge 0 since it has 6 valence electrons. This is favorable for boron rather than having a complete octet.

Amy Kumar 1I

You use the equation to find uncertainty in position or velocity, depending on what is given. If, for example, the velocity is given as 10 +/- 2 m/s, delta(velocity) would be 4 m/s and the question may ask you to find the difference in position (delta(position)) while the mass remains constant.

Amy Kumar 1I

Yes. A bond represents 2 electrons being shared.

Amy Kumar 1I

Triple bonds allow the octet to be satisfied for each element.

Amy Kumar 1I

Make sure you keep your units constant though. In this case, your answer would be in mL too.

Amy Kumar 1I

You should try to get the central atom to have a formal charge of 0, and if it is allowed to have an expanded octet, it can have more than 8 electrons.

Amy Kumar 1I

A bowling ball of mass 8.00 kg is rolled down a bowling alley lane at 5.00 +/-5.0 m/s. What is the minimum uncertainty in its position?

Is the delta velocity 5.0 m/s or 10 m/s because it says +/- 5.0 m/s?

Amy Kumar 1I

For silver, I would suggest writing the expected electron configuration and then switching the electron from the 5s to the 4d (since you're trying to get 4d^10). For beryllium, just go through the 1s, 2s order.

Amy Kumar 1I

Formal charge indicates the gain or loss of electrons that occurs when a covalent bond is formed since the electrons are shared in a covalent bond.

Amy Kumar 1I

Yes, the brackets are placed around the entire structure with the charge in the corner to show the whole molecule's charge.

Amy Kumar 1I

That shape is the resonance hybrid and it depicts the bond length as relatively equal rather than some being stronger than others. For example, the c-c single bond in benzene has a length of 1.54 Angstroms while the c=c double bond in benzene has a length of 1.34 Angstroms. Experimentally, however, ...

Amy Kumar 1I

The formal charge of the central atom might not always be 0, but as long as the the sum of all the formal charges add up to the charge of the overall molecule, it's fine.

Amy Kumar 1I

The purpose is to show that there may different possible ways that the bonds can be formed while the overall charges remain the same.

Amy Kumar 1I

Since there are fewer electrons but the same number of protons, the protons have a greater pull on the fewer number of electrons, therefore those electrons are drawn in closer to the nucleus, making the size of the cation smaller.

Amy Kumar 1I

How do we know if the magnetic quantum number for orientation for the p orbital is -1,0,1 in relation to px, py, and pz?

Amy Kumar 1I

Is there any way to know whether the electrons ms quantum number of -1/2 or +1/2?

Amy Kumar 1I

The parallel spins are from electrons occupying empty orbitals first. After that, they start to pair up, which leads to opposite spins.

Amy Kumar 1I

Electrons occupy orbital individually first so the spins are parallel. Once the available orbitals have been filled, they start pairing up, which is where the opposite spins come from.

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