CHEMISTRY COMMUNITY

manisha_joseph_1H

To determine which elementary step is the one that determines the overall rate, I believe you need to know the experimentally determined rate law of the reaction given. When given this, you are able to figure out which compound the overall reaction rate depends on and compare this with the different...

manisha_joseph_1H

X is the time while Y is the concentration. Together on a graph, these two variables represent the rate of the reaction as time goes on.

manisha_joseph_1H

Rate laws are experimentally determined as they depend on the unique values of k (which varies depending on the reaction) and the concentrations of reactants that are involved.

manisha_joseph_1H

The first equation describes a zero order reaction and the second equation describes a first order reaction.

manisha_joseph_1H

The overall order of a reaction can be found by summing the orders of the individual reactants.

manisha_joseph_1H

Yes, the expression cathode - anode can be used to find the E naught value of the cell when directly using the standard reduction potentials of the compounds given. If we were to flip one of the half-reactions to reflect oxidation instead of reduction, then we would simply change the sign of the sta...

manisha_joseph_1H

Yes, you are still allowed to post! There will just be no additional points awarded beyond 50 in the gradebook.

manisha_joseph_1H

The best oxidizing agent is the compound that is most likely to be reduced. Therefore, when looking at reduction potentials of different compounds, the one that is highest in value is most likely to be reduced and therefore makes a good oxidizing agent. Hope that helps!

manisha_joseph_1H

When work is done on the system, the value of w is positive, When work is done by the system, the value of w is negative.

manisha_joseph_1H

Potential refers to the driving force for the electrons, in this case, the ability for a cathode to pull the electrons as a result of an oxidation reaction towards itself in order to reduce a compound.

manisha_joseph_1H

I believe a reduction is spontaneous if the standard reduction potential of that compound is positive.

manisha_joseph_1H

The anode is the electrode in which the electrical energy moves into, which is placed in the solution where a compound is being oxidized (positive side). The cathode is the electrode in which the electrical energy flows out of, which is placed in the solution where a compound is being reduced (negat...

manisha_joseph_1H

A thermodynamically stable compound means a compound with no thermodynamic tendency to decompose into its elements, which is indicated by a positive standard Gibbs free energy of formation. A thermodynamically unstable compound means a compound with a thermodynamic tendency to decompose into its ele...

manisha_joseph_1H

If Q < K, then the forward reaction is favored and therefore the formation of products. This is because if Q < K, the denominator of the reaction quotient becomes larger which means that the concentration of the reactants is increasing. Since the concentration of the reactants is larger than that of...

manisha_joseph_1H

A salt bridge is used to allow ion transfer between the two solutions of the cell, therefore helping both solutions remain neutral. This allows for electron flow to continue between the two solutions and do work as there is not a difference in charge between the two solutions to disrupt this flow (i...

manisha_joseph_1H

A salt bridge allows for ion transfer between the two solutions, which allows for the two solutions to stay neutral and for electron transfer to continue until a switch is opened and prevents electron flow from occurring. For instance, the solution on the right will become very negatively charged as...

manisha_joseph_1H

Hi! Just as said, we can assume conditions of constant pressure as Cp describes the molar heat capacity of a gas at a constant pressure. However, I'm sure the question will make it clear as to what conditions the system is under, for instance if it told you that there was a change in volume or if it...

manisha_joseph_1H

N represents the amount of moles of a substance in this equation. However, as stated above, you can use the mass of a substance if given the specific heat capacity (heat required to raise temp of 1g of substance by 1 degree C).

manisha_joseph_1H

I think it depends on the context of what you are being asked. For instance, if using heat capacity, then you may be able to keep the temperature units in Celsius as this is the unit given by heat capacity. Similarly, if you are asked to calculate entropy, it will probably be best to use Kelvin as o...

manisha_joseph_1H

I don't believe degeneracy has any units associated with it since it simply describes the number of ways of achieving a given energy state, a quantitative value as discussed above.

manisha_joseph_1H

An increase in volume corresponds to an increase in entropy has there are more positions for a molecule to be in. An increase in temperature corresponds to an increase in entropy because this affects the rate of movement of the particles, causing more disorder (entropy).

manisha_joseph_1H

A closed system does not have to be insulated, but rather sealed from the surroundings. As such, matter can not be exchanged between the system and the surrounds, but energy can. For example, a beaker that is sealed can still be heated or cooled, which signifies a change in energy as the temperature...

manisha_joseph_1H

According to the 2nd law of thermodynamics, delta S = q/T. As such, when q is a positive value, the change in entropy will be positive as well. Since the delta S value is positive, this means that there is an increase in entropy. Hope this helps!

manisha_joseph_1H

When calculating K, the units of the numerator and denominator cancel, so there are no units associated with K. In this case, K just represents the ratio of products to reactants at equilibrium.

manisha_joseph_1H

When calculating K, the units of the numerator and denominator cancel, so there are no units associated with K. In this case, K just represents the ratio of products to reactants at equilibrium.

manisha_joseph_1H

Q refers to heat while H refers to enthalpy. The only time these can be interchanged is under conditions of constant pressure, when q = delta H.

manisha_joseph_1H

A negative q value corresponds to a release of heat by the system, while a positive q value corresponds to an input of heat into the system from the surroundings. Hope this helps!

manisha_joseph_1H

An endothermic reaction requires heat in order to continue. Therefore, an increase in temperature will cause an endothermic reaction to shift in favor of the products. Because this shift in the reaction favors the products, this means the concentrations of the products increase. Since the concentrat...

manisha_joseph_1H

In exothermic reactions, heat is released into the surroundings and therefore the temperature of the surroundings increases. For instance with the calorimeter, if the temperature of the water increased, this means that the reaction is exothermic. In contrast, endothermic reactions require heat, of w...

manisha_joseph_1H

We can assume that x is insignificant in the case of 0.32 - x for instance when the Ka, Kb, or K given is less than 1.0 x 10^-4 and the percent ionization or deprotonation is less than 5%.

manisha_joseph_1H

I believe on Sapling, they consider HClO3 to be a strong acid, so that's what I am going with!

manisha_joseph_1H

A closed system means that there is no exchange of matter between the system and its surroundings, therefore the volume of the system cannot change.

manisha_joseph_1H

We used zoom proctoring for exams in 14A, so I assume that it will be the same for exams in 14B :)

manisha_joseph_1H

Yes, I believe the standard enthalpy of formation is measured at standard conditions for the given reaction.

manisha_joseph_1H

Hess's Law describes the idea that the change in enthalpy in any chemical reaction is a fixed quantity independent of the path or the number of steps taken to obtain the reaction. As such, for a multi-step reaction, you can add the enthalpy change at each step to get the total enthalpy change.

manisha_joseph_1H

Yes, I believe you can have both a periodic table and a constants and equations sheet with you while taking the midterm as long as no extra information is written on them.

manisha_joseph_1H

A phase change describes a change in one state of matter to another. For example, a solid changing to a liquid through fusion or a liquid changing to a vapor through vaporization.

manisha_joseph_1H

Monoprotic describes a compound that can only donate one proton or H+ to another compound.

manisha_joseph_1H

I'm not completely sure, but I think it's best to have 5 posts per week just to make sure you are on track to have 50 posts by the end of the quarter. Also, the syllabus says that you earn 5 pts per week for posting on Chemistry community, so I'm assuming they prefer that you complete 5 posts per we...

manisha_joseph_1H

We leave out H2O because its concentration does not change significantly enough to where it needs to be considered in the calculation of the equilibrium constant.

manisha_joseph_1H

I believe ionization occurs when a compound donates a H+ to another molecule, such as water. Protonation occurs when a molecule gains a H+ from another molecule. Percentage protonation is calculated in the same way as percentage ionization, except you are now dividing the concentration of the compou...

manisha_joseph_1H

Hi! Just as stated above, I believe that the molarity units in the ICE table do not have to be mol/L. As long as all the units in the ICE table are the same, you will be able to carry out your calculation. Just remember to be aware of what units your final answer needs to be in!

manisha_joseph_1H

Yes, that is correct. Changing the volume has an affect on the concentration of the reactants and products, which ultimately will change the value of Q and cause the reaction to either shift to the left or right depending on the relation between Q and K.

manisha_joseph_1H

A difference in pressure will only have an affect on Q when it is due to a change in volume. This change in volume will have an affect on the concentration of either the reactants or products, which will ultimately change the value of Q and shift the reaction to either the right or left.

manisha_joseph_1H

Yes, you do not need to include the concentrations of solids or liquids in the ICE box chart as their concentrations do not change significantly to the point where they would have an affect on K.

manisha_joseph_1H

A change in the concentration of the reactants or products will initially have an affect on the reaction, however, after a certain amount of time has passed, the reaction will return to equilibrium and K will remain unchanged.

manisha_joseph_1H

Yes, that is correct. Adding an inert gas into a reaction does not change the moles of the products and reactants or the volume encompassed by the container. As such, the concentration of products to reactants does not change, meaning there will be no affect on the reaction and K will remain the same.

manisha_joseph_1H

I believe there will be a recorded review session posted on Friday around the same time that we normally have class.

manisha_joseph_1H

Hi! I'm guessing that since we haven't been tested on acids and bases yet, there may be a fair amount of questions on the final asking us about this topic. However, I am not positive as we did not spend a lot of time going over this topic.

manisha_joseph_1H

Yes, the last lecture is on Wednesday! There will be a review session on Friday in which Professor Lavelle will go over different topics.

manisha_joseph_1H

Yes, alkaline solutions are the same as basic solutions! Both refer to a solution with a pH greater than 7, meaning there is a higher concentration of OH- than H3O+.

manisha_joseph_1H

I believe the final will follow a similar format as our previous midterms. As such, there will probably be a mixture of questions from the textbooks as well as conceptual questions that test our understanding.

manisha_joseph_1H

I'm taking 14B in the winter and plan on taking 14BL in the spring as that fits best with my schedule, but I think it is completely fine to take both of them at the same time!

manisha_joseph_1H

Yes, I believe the that the number of e- pairs a ligand can donate corresponds with the type of -dentate it is! For instance, a ligand that can donate 2 e- pairs would be considered a bidentate.

manisha_joseph_1H

For the naming of coordination compounds, you must list the ligand names in alphabetical order. When listing the names of the ligands in alphabetical order, the greek prefixes are not taken in to account. For instance, the name of the coordination compound [Co(NH3)5Cl] Cl.2H2O is pentaamminechloroco...

manisha_joseph_1H

Yes, the pH does indicate the strength of an acid. A strong acid is determined by the amount of protons produced in solution. For instance, a liquid with a pH of 1 produces more protons in solution than a liquid with a pH of 3, thus making the first liquid a stronger acid.

manisha_joseph_1H

Ligands are ions or molecules that bind to a central metal atom to form a coordination complex, often involving the donation of one or more of its electron pairs. Ligands are important as they play a key role in certain biological systems, such as hemoglobin which was mentioned in Professor Lavelle'...

manisha_joseph_1H

OH- is not a radical. If we look at its molecular structure, the oxygen and hydrogen atoms are connected by a single bond, leaving 3 lone pairs around the oxygen atom. We know that O has 6 valence electrons and H has 1 valence electrons, making the total number of valence electrons for this molecule...

manisha_joseph_1H

Yes, I believe that is all we need to take into account at the moment. By knowing the geometrical shape of the molecule, we are able to determine the bond angles present in the molecule. However, by factoring in the number of lone pairs on the central atom, we can determine what affect this may have...

manisha_joseph_1H

A delocalized pi bond is present when there are resonance structures present with shifting double or triple bonds. For instance, benzene or C6H6 has two resonance structures in which the double bonds that connect the carbon atoms can be repositioned. As such, there would be delocalized pi bonds pres...

manisha_joseph_1H

To add on, although AsO43- has polar bonds, they are placed in a symmetrical tetrahedral structure (all bond angles 109.5 degrees) in which the dipole moments will cancel.

manisha_joseph_1H

Water would actually have a bent shape due to the two lone pairs of electrons present on the oxygen molecule, pushing the hydrogen atoms down further which results in a shift from a linear molecule to a bent molecule.

manisha_joseph_1H

Hi! I believe in this question, they are referring to intramolecular forces as they give you single molecules to compare rather than multiple molecules interacting with one another (which would be IMF). Additionally, bond strength is referring to the bonds of a single molecule, which also indicates ...

manisha_joseph_1H

Hi! The way I plan on studying for the final is by going over my notes from lecture, as well as taking notes on the book content and completing all the textbook problems as they may show up on the exam themself. Moreover, I will try to complete worksheets from the UA workshops to have a cumulative r...

manisha_joseph_1H

From Professor Lavelle's lectures, the order of repulsion strength from least to greatest is bonding-bonding pair, lone-bonding pair, and lone-lone pair.

manisha_joseph_1H

Hi! I believe the final is cumulative.

manisha_joseph_1H

Hi! I believe that equatorial atoms lie in the same plane in relation to the central atom and axial atoms lie in a different plane that is perpendicular to the central atom.

manisha_joseph_1H

I believe bond character is referring to what type of features the bond is representative of, such as whether it may be an ionic or covalent bond or is the bond length observed more characteristic of a single or double bond between two certain atoms. Hope this helps!

manisha_joseph_1H

Yes, I believe they will be included on midterm 2 as we have not been tested on them yet.

manisha_joseph_1H

Ground-state electron configuration simply means that none of the electrons a part of this system are in an excited state, meaning that this electron configuration is the most stable and has the lowest energy. I believe that most of the time, electron configuration signifies ground-state electron co...

manisha_joseph_1H

Hi! You were correct in identifying that hydrogen bonds could form with the two nitrogen atoms and four hydrogen atoms. I believe that water can also form 2 hydrogen bonds with the oxygen atom due to its high electronegativity in relation to carbon, meaning that oxygen would have a partial negative ...

manisha_joseph_1H

Hi! I believe the exceptions to the octet rule that we have covered have been an expanded octet which can occur when an element is in row 3 or lower on the periodic table due to the d-orbitals present, and molecules that can have less than an octet for a short period of time due to their high reacti...

manisha_joseph_1H

I believe that the other exception to the octet guideline we have gone over is the concept of an expanded octet, in which an element can have more than 8 valence electrons. There may be more, but I think these are the only two we have covered so far. Hope this helps!

manisha_joseph_1H

I believe elements can have an expanded octet when they are located in row 3 or lower on the periodic table, as they have that additional d-orbital in their valence shell that can accommodate more electrons (resulting in more than 8 valence electrons). Hope that helps!

manisha_joseph_1H

I believe you have to post at least 5 times a week to have a total of 50 posts by the end of the quarter. If you post more than 5 times a week, these extra posts do not roll over towards the next week. Hope this helps!

manisha_joseph_1H

In his lecture, Professor Lavelle said that it would not be favorable for B to have a double bond with one of the F atoms because this would increase the formal charge of that F atom from 0 to 1. When more atoms have a formal charge of 0 in a Lewis structure, that molecule is more stable, which is w...

manisha_joseph_1H

I believe Professor Lavelle included the addition of the flourine atom to highlight how the donation of 2 electrons from this atom gives boron a full octet when it is bonded to BF3.

manisha_joseph_1H

Configurations of electrons can simplify to noble gases when a subshell is complete. For instance, the electron configuration of carbon, 1s^2 2s^2 2px^1 2py^1, can be simplified to [He] 2s^2 2px^1 2py^1. In this case, 1s^2 corresponds to a completed subshell, which holds true for the element Helium....

manisha_joseph_1H

A nodal place is where the probability of finding an electron is 0. For instance, s orbitals have no nodal planes, which therefore leads to a symmetric electron density distribution. However, any orbital beyond this (such as p, d, or f) all have nodal planes, which leads to a non-symmetric electron ...

manisha_joseph_1H

I believe we are supposed to have 20 posts.

manisha_joseph_1H

The Heisenberg Uncertainty equation should be used when dealing with a problem that includes the components of position (such as the diameter of an atom), mass, and velocity (mv = momentum (p). Moreover, a question will most likely ask you to determine the uncertainty in either the position, velocit...

manisha_joseph_1H

Yes, I believe this statement is true. For instance, if you were to increase the principal quantum number from 1 to 2, this would result in the number of orbitals going from 1 to 3, as you now have the 1s, 2s, and 2p orbitals as opposed to the initial 1s orbital.

manisha_joseph_1H

No, the frequency (v) is not the same thing as energy level (n). For this problem, you want to use the equation v = R(1/n1^2 -1/n2^2). Since you are given the wavelength of the spectral line, you are able to find the frequency of this wavelength by plugging into the equation c = wavelength x frequen...

manisha_joseph_1H

I believe in the lecture Professor Lavelle mentioned that anything with a wavelength of 10^-15 m or greater will have measurable wavelike properties and anything less than this will not.

manisha_joseph_1H

For this diagram, I think all you need to know is that a standing wave occurs when the ends of the waves connect and that these waves must be in phase (peaks and troughs match up) in order to create this standing wave.

manisha_joseph_1H

I believe as long as the mass of the object that is plugged into the equation results in a wavelength of 10^-15 m or greater, then the object will have detectable wavelike properties. For instance, if the mass of the object is very large, then this will result in a smaller wavelength and decrease it...

manisha_joseph_1H

I think the one assumption that de Broglie makes at the end of his derivation was that this equation works for any particle with momentum (mass x velocity), which of course was proven to be correct.

manisha_joseph_1H

Yes, an electron is more stable when it is bound and at a lower energy level (such as ground state). As an electron becomes more excited and increases in energy level, there is a higher likelihood of the electron being ejected from the atom, making it more unstable.

manisha_joseph_1H

The intensity of light refers to the number of photons. Therefore, increasing the intensity of the light would increase the number of photons. However, in the case of the photoelectric experiment, the photons need to have a specific energy which is greater than or equal to the energy of the electron...

manisha_joseph_1H

Quanta is used to describe any substance that holds a discrete quantity of energy proportional in magnitude to the frequency of the radiation it represents. Therefore, the word "quanta" is used to describe photons because they are packets of discrete energy. Essentially, quanta is a broad ...

manisha_joseph_1H

Based on what I've read, black holes are near-perfect black bodies that absorb almost all frequencies of light and emit black body radiation. However, radiation with a wavelength equal to or larger than the diameter of the hole may not be absorbed, so they are not considered perfect black bodies.

manisha_joseph_1H

Yes, photons are essentially just packets of energy. They are referred to as "quanta" because each photon holds a discrete (or specific) quantity of energy.

manisha_joseph_1H

Stoichiometric coefficients do not have units associated with them, but rather they show how many atoms, molecules, or formula units are present in a substance. Subsequently, you can multiply these values by 6.0221 x 10^23 (or 1 mol) as a mole could represent any of these, which gives rise to the co...

manisha_joseph_1H

In this problem, we are given the initial volume of the fertilizer solution (1.0 L) and the initial concentration of NH4NO3 (0.20 M). However, this solution is being diluted with 3.0 L of water, meaning there will be a new volume and concentration of NH4NO3 of the solution. To find the new volume of...

manisha_joseph_1H

In a chemical reaction, it is highly unlikely that two reactants are both present in limiting molar amounts. Therefore, it is highly unlikely that there would be two limiting reactants.

manisha_joseph_1H

Once you have calculated the empirical formula of the specified compound, calculate the molar mass of the empirical formula. Then, compare this to the molar mass given in the question for the specified compound. If these two values are the same, then the empirical and molecular formulas are the same...

manisha_joseph_1H

I think Dr. Lavelle was trying to explain how combustion, burning, or oxidation undergo a similar chemical reaction. For instance, in all of them, some sort of burning is taking place in the presence of oxygen. This then leads to the releasing of products, such as carbon dioxide and water, which I b...

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