CHEMISTRY COMMUNITY

Alexandra Bartolome 2H

If a catalyst is added to lower activation energy, the reaction will be able to take place.

Alexandra Bartolome 2H

What does it mean when kinetics rather than thermodynamics is controlling a reaction?

Alexandra Bartolome 2H

A concentration cell has an anode and cathode made up of the same substance whereas in a galvanic cell, the anode and cathode are different substances.

Alexandra Bartolome 2H

an example is: Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s),
where the anode is on the left of the salt bridge and the cathode is on the right

Alexandra Bartolome 2H

The purpose of the salt bridge is to prevent charge buildup; it is made up of a concentrated aqueous salt solution in an inverted, U shaped tube that allows the flow of ions that don't affect the cell reaction.

Alexandra Bartolome 2H

When there's no solid metals present and it's only aqueous components, then you would add an inert metal.

Alexandra Bartolome 2H

Increasing the size of the metal does not cause a change in Ecell.

Alexandra Bartolome 2H

E standard cell is the standard cell potential under standard conditions, such as all solutes present at 25 degrees C, 1 mol/L; all gases at 1 bar. Ecell would be cell potential under non-standard conditions.

Alexandra Bartolome 2H

Q = [products]/[reactants] so it would be [anode]/[cathode]

Alexandra Bartolome 2H

The approach is different since the arrangement of components in electrolytic cells is not the same as in galvanic cells. With electrolytic cells, the two electrodes usually share the same compartment.

Alexandra Bartolome 2H

n would be the moles of electrons being transferred

Alexandra Bartolome 2H

The Nernst equation is used to determine the direction of electron transfer under nonstandard conditions since cell potential depends on the concentration of products to reactants.

Alexandra Bartolome 2H

Using a positive sign helps to clearly indicate a positive charge of voltage/a positive "potential difference"

Alexandra Bartolome 2H

Electrodes are metallic conductors that are in contact with but separated by electrolytes. Electrolytes are aqueous solutions of ionic compounds (basically ions) that act as a medium for the current flow.

Alexandra Bartolome 2H

K is used for redox reactions at equilibrium since K is the equilibrium constant. Electron flow does stop at equilibrium since the concentration changes to the point where Q = K and the cell potential becomes 0.

Alexandra Bartolome 2H

The symbol indicates that the value of the variable is when the variable is at standard conditions, like at 1 ATM or at 298K.

Alexandra Bartolome 2H

Yes, 2 would be n since n is the number of electrons being transferred, but make sure your half-reactions are balanced!

Alexandra Bartolome 2H

The equation that represents the relationship between work and cell potential is: wMAX = - n F E. wMAX is the work done, which is also equal to ∆G, the change in Gibbs free energy.

Alexandra Bartolome 2H

Free energy and cell potential are related through the equation ∆G = - n F E, where ∆G is the change in Gibbs free energy, n is the number of electrons being transferred, F is Faraday's constant, and E is the cell potential.

Alexandra Bartolome 2H

In the equation, n is the number of electrons in moles that is being transferred.

Alexandra Bartolome 2H

Why does oxidation take place at the anode and why does reduction take place at the cathode?

Alexandra Bartolome 2H

reduction: gain of electrons, charge becomes more negative
oxidation: loss of electrons, charge becomes more positive

I don't think it has to do with proton transfer since it has to do with a gain or loss of electrons.

Alexandra Bartolome 2H

oxidation: loss of electrons
oxidizing agent: causes oxidation and gets reduced in the process

Alexandra Bartolome 2H

Since oxidation and reduction reactions happen together, the number of electrons released by oxidation needs to be the same as the number of electrons used in reduction due to the fact that in chemical reactions, electrons are neither created nor destroyed.

Alexandra Bartolome 2H

^^ Like what they said, an oxidation half-reaction and reduction half-reaction are part of an overall redox reaction. Writing the half-reaction is a conceptual way of showing just the oxidation part of the redox reaction or the reduction part. The electron is not actually free, it's in transit unlik...

Alexandra Bartolome 2H

Intensive properties are properties independent of the quantity of the substance. One example is specific heat capacity since it is specified/normalized to 1 gram of a substance. Extensive properties do depend on the amount of a substance, like heat capacity.

Alexandra Bartolome 2H

In an open system, both matter and energy can be exchanged with the system and surroundings.

Alexandra Bartolome 2H

Why does lead have a higher molar entropy than carbon?

Alexandra Bartolome 2H

For a heating curve, q is on the x axis and the temperature is on the y axis. When you have a steep slope, this means that for smaller increases in q (heat), there are larger increases in temperature, which correlates to a lower heat capacity. When you have a more flat slope, for larger increases in...

Alexandra Bartolome 2H

The heat supplied to cause a substance's phase change does not actually change the heat of the substance.

Alexandra Bartolome 2H

When does qp = ΔH?

Alexandra Bartolome 2H

When bonds form, they become more stable, which means they release energy.

Alexandra Bartolome 2H

During phase transition, why does the temperature of the sample remains constant even though heat is being supplied?

Alexandra Bartolome 2H

You would multiply so that the moles cancel out and you are left with the units kJ.

Alexandra Bartolome 2H

Is a regular calorimeter also an insulated system like a bomb calorimeter or is it a closed system?

Alexandra Bartolome 2H

D is an open system because it has interactions externally with the environment, it is releasing energy into the air. C is a closed system because the bomb calorimeter is designed to keep gases in so no gas is released to interact with the environment. Why is C a closed system? Wouldn't a bomb calo...

Alexandra Bartolome 2H

Solvents tend to be liquid (l), thus won't be included in equilibrium constant calculations. Additionally, solids won't be included as well, due to their activities being equal to 1. Aqueous solutions and gases are always included.

Alexandra Bartolome 2H

The reaction is endothermic. Energy has to have been absorbed in order for the products to have a higher energy than the reactants.

Alexandra Bartolome 2H

I believe when K is less than 10^-3, you can approximate with the 5% rule.

Alexandra Bartolome 2H

No because you don't need to include them in calculating equilibrium constants.

Alexandra Bartolome 2H

A student added solid Na2O to a volumetric flask of volume 200.0 mL, which was then filled with water, resulting in 200.0 mL of NaOH solution. Then 5.00 mL of the solution was transferred to another volumetric flask and diluted to 500.0 mL. The pH of the diluted solution is 13.25. (a) What is the mo...

Alexandra Bartolome 2H

When calculating the percent ionization and it is less than 5%, it confirms that the approximation of x in the ICE table is okay and the use of the quadratic formula is not necessary.

Alexandra Bartolome 2H

Q is calculated the same was as K. However, K is the equilibrium constant while Q is the reaction quotient at any time during the reaction. You compare Q to K in order to find out whether the reaction is at equilibrium or not. When Q<K, the forward reaction is favored since the concentration of reac...

Alexandra Bartolome 2H

When finding the percentage protonated, whatever is receiving a proton is being protonated. A base accepts protons. You'll need to know if it is protonated depending on what the question is asking.

Alexandra Bartolome 2H

Ka uses the concentration of hydronium ions, so you would usually use it when dealing with acids. Kb uses the concentration of hydroxide ions, so you would usually use it when dealing with bases.

Alexandra Bartolome 2H

It is unitless because in the calculation of the equilibrium constant, you're using the activities of the reactants and products, as someone else said. Section 5G.2 in the textbook pretty much explains why it's unitless: "Thus, for a substance J that forms an ideal solution, the partial pressur...

Alexandra Bartolome 2H

K would be 1 since the activities of solids and liquids are all 1.

Alexandra Bartolome 2H

You use Kc when given molar concentrations of reactants and products. You use Kp when dealing with the partial pressures of reactants and products, which are in the gas phase.

Alexandra Bartolome 2H

You use K when calculating the equilibrium constant when the reaction is at equilibrium. Q is the reaction quotient used to determine whether a reaction not at equilibrium will favor reactants or products.

Alexandra Bartolome 2H

Reactants and products that are in the aqueous state are included. As the other person said, it's pretty much used with Kc.

Alexandra Bartolome 2H

In lecture, Lavelle said that if the value is between the two limits neither the reactant nor the product is favored and it is in a sort of intermediate state. Does that mean that we most likely won't be asked a question on whether the reactants or products are favored if the K value falls between ...

Alexandra Bartolome 2H

Why do salts of weak bases produce acidic solutions? Why do salts of weak acids produce basic
solutions?

Alexandra Bartolome 2H

Why do solutions of weak acids have higher pH values than solutions of strong acids at the same concentration? Is it simply because solutions of weak acids have less hydronium ions present than solutions of strong acids?

Alexandra Bartolome 2H

How is a solution's pH related to hydronium ion and hydroxide ion concentrations?

Alexandra Bartolome 2H

What is the difference between amphiprotic and amphoteric?

Alexandra Bartolome 2H

Ligands are considered Lewis bases since they are electron pair donors.

Alexandra Bartolome 2H

Coordination number is basically the number of bonds the central atom has with ligands.

Alexandra Bartolome 2H

Coordination compounds with 6 ligands are octahedral complexes, with 4 ligands are either tetrahedral or square planar, and with 2 ligands are linear.

Alexandra Bartolome 2H

A Lewis base is an electron pair donor, so it can be an atom or molecule that donates an electron pair.

Alexandra Bartolome 2H

Ligands must have one or more lone pairs. When it has one lone pair of electrons, it is mono-dentate and binds with the central metal atom. When it has more than one lone pair, it can occupy more than one binding site at once and this can be labeled as chelating.

Alexandra Bartolome 2H

A complex always consists of central metal atom/ion attached to other molecules and ions through coordinate covalent bonds.

Alexandra Bartolome 2H

Cis molecules are polar since the bonded atoms that are the same are next to each other. Trans molecules are nonpolar since the bonded atoms that are same are located opposite each other.

Alexandra Bartolome 2H

The coordination sphere consists of the ligands directly attached to central transitional metal ion.

Alexandra Bartolome 2H

The coordination sphere is made up of the ligands directly attached to the central transition metal cation.

Alexandra Bartolome 2H

What is the difference between a transition metal complex and an organometallic complex?

Alexandra Bartolome 2H

Yes. A striking property of d-block elements is that they are able to form coordination compounds.

Alexandra Bartolome 2H

Jorge Ramirez_4H wrote:Does weight not affect angles?

No because the bond angles are formed from the repulsion between lone pairs and bonding electrons.

Alexandra Bartolome 2H

Single, double, triple bonds are all considered single regions of electron density in the VSEPR model.

Alexandra Bartolome 2H

It's not necessary but it's always helpful so that you can see the locations of bonding electrons and lone pairs then use the VSEPR model and determine the structure.

Alexandra Bartolome 2H

A molecule will have linear structure when the central atom has no lone pairs. This is because the bonding pairs will lie on opposite sides of the central atom to be far apart. Examples are H2O and BeCl2. It helps to draw Lewis structures.

Alexandra Bartolome 2H

How do we tell if the structure is going to be bent versus linear? BeCl2 has no lone pairs on the central atom, beryllium. The two bonding pairs are on opposite sides of the Be atom to be far away from each other, so the structure is linear. The same goes for CO2; the central atom, carbon, has no l...

Alexandra Bartolome 2H

Yes, molecules with bent/angular structures are something that we went over in class. An example is H2O.

Alexandra Bartolome 2H

I don't think there's a specific length of time; it's simply an instant since there's always fluctuations with electron distribution.

Alexandra Bartolome 2H

Dispersion forces act between all atoms and molecules, not within one atom, because they are attractive interactions.

Alexandra Bartolome 2H

An ion-dipole force occurs between an ion and a dipole/the partial charges of polar molecules. The attraction between a Cl anion and the polar H2O molecule is an example of this force.

Alexandra Bartolome 2H

London dispersion forces and induced dipole-induced dipole can be used interchangeably. Electron distribution in atoms and molecules fluctuates which results in fluctuating dipoles and the interactions are always present and attractive.

Alexandra Bartolome 2H

I know that electrons in atoms or molecules can cause electron distortion in nearby atoms or molecules but what exactly is electron distortion? Why do ions with high electron distortion also have high polarizing power?

Alexandra Bartolome 2H

It's a bond where both electrons come from one atom, completing the octet of an atom existing in a compound with an incomplete one. The example provided in class and in the textbook was that of boron trifluoride BF3, and boron has only six valence electrons. Its octet is completed when it forms a co...

Alexandra Bartolome 2H

In ionic bonds, there's a transfer of electrons from a metal to nonmetal atom. In covalent bonds, non-metals share electrons. But, many bonds have both ionic and covalent characteristics. Roughly, an electronegativity difference between atoms that is greater than 2 indicates an ionic bond, an electr...

Alexandra Bartolome 2H

A covalent bond has ionic properties when there's unequal charges/charge asymmetry since the electron pair in the bond may not be equally shared. The extent of the ionic properties depends on the electronegativity of each bonding atom, like what the other person said. Atoms with high electronegativi...

Alexandra Bartolome 2H

Okay, then let's say it's a different element like Carbon. Would it still be following the rule? Lewis structures show how atoms are bonded together, and atoms bond together to achieve an octet so atoms in a Lewis dot structure should be following the octet rule. Also, I think it is more accurate t...

Alexandra Bartolome 2H

Obtaining a formal charge of 0 is more important since it means that although the octet rule is reached, the atoms have exactly a half-share in a pair of bonding electrons.

Alexandra Bartolome 2H

I thought that resonance structures were "ideal" when the formal charges of the atoms were equal to 0? Or close to that value in some cases. Wait yes, the "ideal" structure is as you said, when the formal charges of the atoms are at 0, since the formal charges of atoms in a mole...

Alexandra Bartolome 2H

Helium probably wouldn't bond with other elements because it is already stable as a noble gas. Noble gasses are known not to react with other elements. Okay, then let's say it's a different element like Carbon. Would it still be following the rule? Lewis structures show how atoms are bonded togethe...

Alexandra Bartolome 2H

Polyatomic molecules have resonance when it has Lewis structures with multiple bonds that can be placed in different but equivalent locations. The real structure is a blend of the polyatomic molecule's different Lewis structures, which is resonance.

Alexandra Bartolome 2H

Yes because an anion has a negative charge and a cation has a positive charge. Nonmetal atoms form anions with an octet corresponding to the configuration of the following noble gas.

Alexandra Bartolome 2H

Both are used to determine ground state electron configuration. With the Pauli Exclusion Principle, electrons in the same orbital must have different spins. With Hund's rule, electrons must occupy different orbitals singularly, with the same spin before doubling up.

Alexandra Bartolome 2H

I would assume so since Professor Lavelle's outline for The Quantum World lists that we should understand the relationship between Schrodinger's Equation, wave functions, and orbitals.

Alexandra Bartolome 2H

Wave functions represent the probability of finding the position of an electron in an atom. They are used to describe an electron, which has wavelike properties and indeterminate momentum/position, in an atom.

Alexandra Bartolome 2H

Atomic spectra shows that light has particle-like properties. Electrons in atoms and molecules absorb/emit discrete packets of energy. Spectral lines result from a transition between two energy levels, and the difference in energy is emitted as a photon.

Alexandra Bartolome 2H

I am still a bit confused on the concept of wavefunctions. From my understanding, wavefunctions represent the varying positions of particles since they have wave-like properties and do not have precise trajectories. How does this relate to orbitals?

Alexandra Bartolome 2H

Leila_4E wrote:What is the work function?

The work function is the energy needed to remove an electron from a metal.

Alexandra Bartolome 2H

If that is true ( if excess energy is used to emit electrons and since the electrons are moving, the excess energy is basically manifested as the kinetic energy of the electron) then what would be the kinetic energy when the threshold energy is met exactly? If I am not mistaken, the kinetic energy ...

Alexandra Bartolome 2H

Just to clarify, the work function of a metal is the same as the threshold energy, the minimum amount of energy required to eject electrons from a metal surface?

Alexandra Bartolome 2H

What causes ultraviolet photons to be more energetic than photons of visible light? Is it simply due to the fact that ultraviolet light has higher frequencies and shorter wavelengths than visible light?

Alexandra Bartolome 2H

One thinking point in the texbook asked why ultraviolet radiation is much more harmful to living tissue than infared radiation... I was wondnerinf if someone could explain the answer. I think this is because ultraviolet radiation has higher frequency and shorter wavelengths than infrared radiation,...

Alexandra Bartolome 2H

I think it would be best to follow sig fig rules, but like what another person asked, which problems in the solution manual ignored sig fig rules?

Alexandra Bartolome 2H

It is possible to go from molecular to empirical. You would just need to get each of the subscripts in the formula and change it so they are at the simplest ratio and still keeping whole numbers. I don't think we would really need to do this though. I think you meant to say that the coefficients in...

Alexandra Bartolome 2H

Yes, it's better and more practical to change fractional coefficients in chemical equations into whole numbers. With whole number coefficients, you could clearly see mole ratios between reactants and products.

Alexandra Bartolome 2H

I think the units should be consistent with what the problem asks you to solve for.

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