CHEMISTRY COMMUNITY

Madelyn Romberg 1H

Its for simplifying ICE calculations. If the end result is less than 5%, than the approximation is accurate.

Madelyn Romberg 1H

Collision theory connects temperature and energy. Molecules need to have enough kinetic energy that, upon collision, there is enough energy to overcome the energy barrier. By increasing temperature, the molecules have a higher kinetic energy and therefore are more likely to overcome the energy barri...

Madelyn Romberg 1H

You can use experimental data by plotting the data using the formulas observed in class and try to achieve a linear plot. If they give you a list of intermediate steps, the slow step will be the rate law which will give indication to the order.

Madelyn Romberg 1H

Either can be used and the steady state is more versatile. But, for Lavelle, we will only be using the pre-equilibrium.

Madelyn Romberg 1H

The slow step should have a rate law that is equivalent to the observed rate law.

Madelyn Romberg 1H

Does this mean that free energy of activation measured without the enzyme? Or is it needed in relation to the activation energy with the enzyme?

Madelyn Romberg 1H

Homogeneous are in the same phase and move around the designated volume like it was a reactant or product. When it is a heterogeneous, it is a different phase and the reactants rest on the surface and are adsorbed.

Madelyn Romberg 1H

Units correlate to the reaction order to ensure the final units work out. Hence, the units for the rate constant will indicate the rate order.

Madelyn Romberg 1H

k_r is the reaction rate constant which relates the rate of the initial concentrations to the rate of the chemical reaction.

Madelyn Romberg 1H

Julia Holsinger_1A wrote:How do you determine the order of the reaction when needing to calculate half life? Will it always be given?

To determine the order, you will likely use scientific data, are told, or can assume pseudo-first reaction if the information permits.

Madelyn Romberg 1H

Half lives can be used to determine how much product is left after any amount of time. if you know the half life, you set the equation: (1/2)^x =1/A where a is the value of how much of the original product remains. For example, 1/9 of the initial amount. Solve for x to see how many half lives there ...

Madelyn Romberg 1H

•OH + CO → •HOCO
•HOCO + O2 → HO2• + CO2

HO2• + NO → •OH + NO2
NO2 + hν → NO + O• , λ<400 nm
O• + O2 → O3

If there is no sunlight available to break NO2, the production of ozone will stop.

Madelyn Romberg 1H

This shows the standard reaction where you want to get exactly one mole of product, which means we use fractions for the reactants if needed.

Madelyn Romberg 1H

How do you know which side is oxidized and reduced in concentration cells?

Madelyn Romberg 1H

It depends on the solution. If it is acidic, you add H+ to balance H. If it is basic, you add h2o to the side that needs H and OH- to the other side.

Madelyn Romberg 1H

Oxidation number related to the charge of the element within its molecule. You compare its charge on each side of the equation. If it becomes more positive, it loses electrons and is therefore oxidized. If it becomes more negative (less positive), it gains electrons and is therefore reduced.

Madelyn Romberg 1H

In basic solutions, H+ is not readily available. To balance H, you add h20 to one side and then oh- to the other. This is essentially adding an H+ in a different manner.

Madelyn Romberg 1H

They do effect the rate of the reactions but to not effect the equilibrium constants.

Madelyn Romberg 1H

That is a sound way to do it. It is about convenience and ease, also considering which mathematical approach you understand the best.

Madelyn Romberg 1H

It is about probability. The probability that a specific set of four molecules not only collide at the exact same time, but with enough energy to break and form new bonds. Through a probability lens, these occurrences are unlikely.

Madelyn Romberg 1H

Catalysis increases the forward and reverse reaction rates by lowering activation energy.

Madelyn Romberg 1H

An activated complex can be a varying number of configurations between two molecules. In the activated complex, the complex can either form products or disassociate to form the original reactants. The transition state is the one of highest potential energy and when this energy level is reached, the ...

Madelyn Romberg 1H

Arrhenius behavior is when the graph of 1/kr is linear when plotted against 1/T

Madelyn Romberg 1H

It depends on the reaction but from what we have been given thus far, it seems as though lavelle will tell us which is the fast and slow step.

Madelyn Romberg 1H

Is the equilibrium constant the same in the presence of a catalyst because the forward and reverse reaction rate increase the same so the ratio stays the same?

Madelyn Romberg 1H

What is the use of molecularity? As in, can I get an example where knowing the molecularity of elementary reactions are helpful?

Madelyn Romberg 1H

You can use pseudo first order when trying to find out how the reaction is dependent on only one reactant. This is done by assuming the other concentrations are very large and do not change, so only our molecule of concern is studied.

Madelyn Romberg 1H

How do reaction mechanisms indicate first or second order? Can i get a description on things to look for to identify and connect the two?

Madelyn Romberg 1H

There is also a helpful page in the book for this which shows how the equation is derived. It is page 606.

Madelyn Romberg 1H

Can someone explain to me how a concentration cell works if it is using the same molecule? As in, where do the electrons come from and go if only one molecule is there for redox reactions

Madelyn Romberg 1H

You are given a table with the initial concentrations and the intial rates for the reaction A+B+C= Products How do you tell if a reaction is zero order with respect to a reactant? Is it if the other two concentrations are the same and only the reactant of interest concentration changes and it still ...

Madelyn Romberg 1H

Max potential occurs right before the cells are connected because the electric potential is the greatest (nothing is flowing between them.) As time goes on, the system heads towards equilibrium and the electric potential decreases.

Madelyn Romberg 1H

I would always double check what is being oxidized and what is being reduced to ensure it is correct.

Madelyn Romberg 1H

A good saying is LEO says GER: Losing Electron Oxidizing, Gaining Electrons Reduction
Looking at the change in the oxidation numbers helps indicate if it is a reduction or oxidation.

Madelyn Romberg 1H

half reactions let you balance how the oxidation and reduction is occurring, bringing in the right number of water, hydrogen, and hydroxide molecules to bring about a balanced redox reaction.

Madelyn Romberg 1H

The system will reach equilibrium where the charges will no longer flow. In terms of a galvanic cell, adding a salt bridge can keep the system "neutral" and allow charges to keep flowing rather than build up.

Madelyn Romberg 1H

While looking at the charges of the cathode and the anode, the cathode has a more positive charge while an anode has a more negative charge. Hence, cathode attract electrons which is associated with reduction and the anode is the opposite, which is associated with oxidation.

Madelyn Romberg 1H

It will be the products minus the reactants to find the net change. This applies to other state functions as well.

Madelyn Romberg 1H

For a reversible reaction, it occurs under constant temperature because it is such a slow and small change that it remains balanced between the internal and external environment.

Madelyn Romberg 1H

If delta H is negative, then to determine if the reaction is spontaneous, you have to look at T*delta S. In order to make G positive given a negative delta H, entropy would have to be negative and overpower the delta H. This is unlikely because the release of energy from an exothermic reaction is un...

Madelyn Romberg 1H

Because there is no net change occurring, no total work is done. That is because the energy is in equilibrium as well.

Madelyn Romberg 1H

If gibbs free energy is less than zero, it is spontaneous. There is a chart in the book to correlate the two parts of gibbs free, the enthalpy and entropy part of the equation.

Madelyn Romberg 1H

Tests themselves are not curved but the grade distribution is based on everyone FINAL grade.

Madelyn Romberg 1H

Closed allows only energy transfer while isolated does not allow the transfer of energy nor matter.

Madelyn Romberg 1H

The energy of the universe is constant, so yes the amount of energy is always the same. However, the form the energy is in is why there is a crises. We combust the fossil fuels and the energy is released, but not back into the form of fossil fuels. Hence, a crises.

Madelyn Romberg 1H

Extensive properties are directly related to the amount of material present. The amount of heat required to rais X amount of a substance one degree is extensive. Density is NOT an extensive property. Whether you have a whole gallon of water or a drop of water, density is the same.

Madelyn Romberg 1H

Work is energy times distance. The way I think of it is: who is losing energy in order to receive the desired change? If the system is compressed, energy must be going into the system and work must be done ON the system in order for this to occur. For the system to expand, it loses energy to the sur...

Madelyn Romberg 1H

Delta H is positive as the system absorbs energy in order to go to a liquid phase AND the energy remains there to keep it in a liquid phase.

Madelyn Romberg 1H

To get to Kelvin, you add 273 to the degrees Celsius. This is a linear relationship so one degree Celsius will be one degree kelvin.

Madelyn Romberg 1H

For work, it is relative to what your are referencing. In terms of this class, the focus is our system. If the system does work, work is positive (the system loses energy). If work is done on the system, it is negative (energy added to the system).

Madelyn Romberg 1H

It is really used for when the pressure isn't constant do to find the work done, it is the integral of the subsequent volume changes. It is also used to derive the first formula.

Madelyn Romberg 1H

I ask myself: can energy leave or enter? Can matter leave or enter?
By answering these, you can find if it is open (yes/yes), closed (no/yes), or isolated (no/no).

Madelyn Romberg 1H

For the bomb calorimeter, their design is made to be an isolated system. This is just a fact listed in the book and the only way you can distinguish it between a closed or isolated system.

Madelyn Romberg 1H

For D, matter and energy can be exchanged into the engine. Therefore, it is an open system.

Madelyn Romberg 1H

Use w=-P∆V
-w=work
-P= pressure
-∆V= change in volume

you are given P and the change in volume can be calculated using the given diameters and some geometric formulas.

Madelyn Romberg 1H

Delta H is a measure of enthalpy whereas Q is the energy in transit. Delta H is a state of the system.

Madelyn Romberg 1H

I have a similar question as above, is anyone able to answer? I would assume it is irreversible since the energy is then lost to heat and cannot be recovered?

Madelyn Romberg 1H

Temperature does not change during a phase change. However, there is still energy being put into the system. The energy is going into breaking intermolecular bonds rather than thermal heat.

Madelyn Romberg 1H

Autoprotolysis is proton transfer between the same type of molecule. In this class, water was the example. 2H20 <-> h3o+ + oh-

Madelyn Romberg 1H

From our current tools given, he will give the change in enthalpy and from that information you will have to determine if it is exo/endo, and he may ask questions that utilize Le Chateliers principle in regards to temp.

Madelyn Romberg 1H

You need to know how to calculate and convert between the two, but memorizing values is unnecessary.

Madelyn Romberg 1H

Temperature can be thought of as a reactant. If adding heat to a reaction, it will favor whichever direction has the positive change in H. This is because forming more of the "energy rich" molecule will harness more of the heat to minimize the net change of temperature of the environment. ...

Madelyn Romberg 1H

It is the variations of energy units. The SI unit is Joules. However, calories/kilocalories are also common and you can convert between Joules and calories.

Madelyn Romberg 1H

I would recommend becoming familiar with it in general though. It will help you timewise to know how to use the formula and not waste time on the math when you can be focusing more on the chemistry at hand.

Madelyn Romberg 1H

Typically it will specify. When given all gases, you will likely use partial pressure. If they specify concentration when given gasses, you may need to use PV=nRT to convert between the two. K is a general symbol which can apply to Kp or Kc. In this class he has had us specify which we are using.

Madelyn Romberg 1H

Yes, this is correct. It is about looking at the concentrations in the Q value to see if the reaction will shift right or left.

Madelyn Romberg 1H

The equation is extremely simplified and ignores all of the moments in which, yes, forming bonds did release energy. However, when thinking about it with common sense, it is an endothermic reaction. First, light (energy) is required for photosynthesis to happen. Secondly, our bodies use glucose as a...

Madelyn Romberg 1H

They are measured the same. The key difference is K is ONLY at equilibrium where as Q is at any point in the reaction. Q can tell us which way the reaction will favor when compared to Q.

Madelyn Romberg 1H

You would get the same answer but it is easier when using whole numbers to calculate--plus, it will then match your balanced equation.

Madelyn Romberg 1H

Temperature can alter the stability of the molecules in the reaction. Hence, by changing the temperature, the products or reactants may become more/less stable at different temperatures. With this information, the reaction my shift to the left or right, altering our K.

Madelyn Romberg 1H

K is an equilibrium constant that is most favorable to the reaction under certain conditions. Q measures where the reaction is at any given time in relationship to K.

Madelyn Romberg 1H

K tells us the ratio of concentrations between products and reactants that is most favorable given the current conditions. So, with changing concentrations, you will be changing your Q. Then, the reaction will work to bring Q towards K. The total amount of product and reactant will change, but their...

Madelyn Romberg 1H

It could be either. Sig figs are based off of the smallest number of sig figs initially measured.

Madelyn Romberg 1H

Carboxylic acids are common of organic chemistry whereas oxacids will appear in general chemistry (with metals)

Madelyn Romberg 1H

Also helpful is to remember Lewis Acids will accept lone pairs and Lewis Bases with donate lone pairs, hence your conclusion was correct

Madelyn Romberg 1H

Always remember water is a product, so there will be a cation paired with a hydroxyl and an anion paired with a H+ ion. So work backwards to fill in the missing pieces

Madelyn Romberg 1H

I believe we will need to be able to remember them; he stated during lecture that we can find the common ligands in the textbook, which makes it seem like we should be familiar with them.

Madelyn Romberg 1H

An important key to remember is the CIS part of the molecule (as a TRANS version does exist). This allows both ligands to bind to the DNA and effectively start replication whereas the TRANS version is unable to do this.

Madelyn Romberg 1H

There are two versions of a molecule that we use to identify shape. The molecular shape does NOT use lone pair electrons when determining shape; however, they play an influence in bond angles that can therefore slightly alter the molecular shape. The electronic geometry of a molecule does consider l...

Madelyn Romberg 1H

When you draw the lewis structure, you will be able to identify how many bonding regions there are. Then, you just need to make sure the hybridization state has the same number of orbitals as bonding regions.

Madelyn Romberg 1H

A rod shaped molecule has stronger intermolecular forces, meaning they have a stronger attraction to each other. To break this stronger connection requires more energy, resulting in a higher boiling point. The opposite is true for the spherical shape.

Madelyn Romberg 1H

A good thing to think about are organic molecules (hydrocarbons, more specifically, alkanes). Van Der Waals forces are a strong contributor to the boiling point of molecules. Longer, more linear alkanes have a stronger Van Der Waals forces and therefore it requires more energy to break this attracti...

Madelyn Romberg 1H

I would make plans for either option and he should tell us in the upcoming classes if it will be canceled

Madelyn Romberg 1H

In a less scientific way, it is easier to break a thin stick that is about 6 feet long (a single bond) rather than a stick that is 3 centimeters long (a triple bond). Hence, single bonds are weaker than double or triple because they are longer.

Note, the chosen lengths are arbitrary.

Madelyn Romberg 1H

When it comes to diagonal elements, it is generally difficult to [censored] their comparing electronegativity because you experience two opposing forces that influence electronegativity. In the case of sodium and calcium, sodium appears to have a higher electronegativity because it is in the period ...

Madelyn Romberg 1H

Can someone explain the difference between dipole-dipole versus dipole-induced dipole?

Madelyn Romberg 1H

Calculating formal charges allows us to draw the most stable structure. For example, it will tell us if we should consider double bonds within the molecules to create more stability.

Madelyn Romberg 1H

How do the electrons move within atoms to create the "blended" characteristic?

Madelyn Romberg 1H

Going off of this question, why does the boron trifluoride atom not form a coordinate covalent bond with the fluorine to get an octet opposed to adding an additional fluorine atom?

Madelyn Romberg 1H

Why do elements such as copper not follow our expected electron configurations

Madelyn Romberg 1H

Are remembering units for this equation, and others, necessary? Or are they given on the test?

Madelyn Romberg 1H

What is the difference between principal quantum number and magnetic quantum number?

Madelyn Romberg 1H

What is the difference between principal quantum number and magnetic quantum number?

Madelyn Romberg 1H

What does the numerical value given by the uncertainty principle actually mean?

Madelyn Romberg 1H

What is the relationship between energy and the shrodinger equation? I do not understand the "operate a change on" part of the notes.

Madelyn Romberg 1H

Can someone explain the concept of nodal planes and their relationship to orbital shapes.

Madelyn Romberg 1H

The scientists expected that increasing the intensity of the light would eject electrons from a metals surface (which did not happen). The scientists then had to change their thought process. Instead of increasing the intensity, they increased the frequency, which ejected electrons. This data reflec...

Madelyn Romberg 1H

How do we detect the electrons whose velocity is zero when the threshold energy and energy of the photon are equal?

Madelyn Romberg 1H

Question: Why does hydrogen emits multiple wavelengths to create its own "fingerprint", yet it only has one electron whose energy level could change can emit the frequencies?

Madelyn Romberg 1H

Can someone confirm the typical notation used for molarity? To clarify, which variables represent what?

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