CHEMISTRY COMMUNITY

Brandon Fujii 1K

I think that we assume that this is an ideal gas because we assume that it only interacts with the water vapor and is not affected by other external forces.

Brandon Fujii 1K

Hi if I recall correctly, Dr. Lavelle gave the example of the throwing tennis balls in the air. The probability of throwing three balls in the air and having them collide at the exact same time is lower than the probability of throwing two balls in the air and having them collide at the exact same t...

Brandon Fujii 1K

Here are the connections that I made for each functional group Alcohol --> Ether (The H in OH becomes an R group) Alcohol --> Aldehyde (Dehydrogenation OH becomes H + O) Aldehyde --> Ketone (H becomes R group = reason why Ketone is in the middle of the carbon chain unlike Aldehydes which are found a...

Brandon Fujii 1K

We cannot simply multiply the half life by a factor of 4 because the half life of a second order reaction is reliant on the initial concentration of the reactant (while the first order half life reaction only relies on the equilibrium constant.) Second order half life equation: 1/k[A] o First order ...

Brandon Fujii 1K

Note that the unique rate is the rate of formation, and the rate of formation for reactants is negative (because reactants are consumed in the reaction). Therefore, we must put a negative sign in front of the reactant's rate of formation to give it a positive value that equals the positive rate of f...

Brandon Fujii 1K

A negative first order would occur if a the rate is halved when the concentration of a reactant is doubled.

Brandon Fujii 1K

Half life can also tell you how fast a substance decays.

ie. A substance that has a half life of 10 seconds has a faster rate of decay in comparison to a substance that has a half life of 10 days.

Brandon Fujii 1K

Although the formulas for Rate Laws and Integrated Rate Laws are given, it is helpful to know how to derive the integrated rate law to have a better understanding of the concepts.

Brandon Fujii 1K

I know that the overall reaction order for:

RATE= k[NH₄⁺]ⁿ [NO₂^-]^m

is n+m (if n=1 and m=1) the overall reaction rate is 2

But what do we call the individual orders (only n or only m)?

Brandon Fujii 1K

How do we solve for Q when we are given both molarity and partial pressure?

What if the partial pressures in 14.37a were different?

Brandon Fujii 1K

Without an inert solid metal conductor, a cell with only aqueous ions would not be able to transfer electrons from the anode to the cathode.

Brandon Fujii 1K

An example might be: if the oxidation half reaction produces 2 mol of e- and reduction half reaction produces 3 mol of e- you’d have to multiply the oxidation half rxn by a factor of 3 and the reduction half rxn by a factor of 2 because the moles of e- must cancel in this case 2mol e- * 3 = 6mol e- ...

Brandon Fujii 1K

Additionally, if you were asked when does Delta U = q, your answer would be:

When w=0 because Delta U=w and q=0 under adiabatic conditions

Brandon Fujii 1K

If you are wondering why Cl₂ has an oxidation number of 0, it is because neutral uncombined atoms or atoms in pure element is assigned an oxidation number of 0.

ex. Cl₂(g), Na(s), Hg(l)

Brandon Fujii 1K

In the image below, the Reducing Agent (A) is oxidized because it loses its electrons. The Oxidizing Agent (B) is reduced because it gains electrons.

Brandon Fujii 1K

You would only use the Cv,m and Cp,m values (3/2R, 5/2R, etc) as the heat capacity for ideal gases. Additionally, if water were a vapor, Cp,m would equal 4R not 5/2R because water is a nonlinear molecule.

Brandon Fujii 1K

Can someone explain why the units for the answers are "kJ/mol"? Since we are decomposing 2 moles of Hydrogen Peroxide, shouldn't the answer be in just "kJ" because we already accounted for the 2 moles of Hydrogen Peroxide? In the Solutions Manual: for part A, delta G is -233.6 kJ...

Brandon Fujii 1K

If we were given 1mol Ar(g) @ 1atm and .5mol Ar(g) (instead of 1mol) @ 2atm would the entropy be the same or would 1mol @1 atm still have more entropy because of its larger volume?

Brandon Fujii 1K

Unless we learn how to calculate the entropy changes for non-ideal gases, I believe that --for this class-- we assume that all gases are ideal gases.

Brandon Fujii 1K

In the internal energy equation

Delta U = q+w

our w value would be negative because the w is work done by the surroundings (system does work to expand)

Brandon Fujii 1K

q=0 because heat is neither released nor absorbed by the system. Therefore, the only energy transfer is done by work (w).

Brandon Fujii 1K

Entropy is also represented by the equation

deltaS= Q_rev/T

Therefore the units of Entropy are J * K^-1

Brandon Fujii 1K

Whenever a substance is being heated AND is not going through a phase change, the temperature of the substance (average Kinetic Energy of each particle) increases. As the total kinetic energy of the particles of the substance increases, entropy increases. Therefore, because a gas has a higher temper...

Brandon Fujii 1K

One can argue that the universe is an isolated system because matter and energy is neither created nor destroyed.

Brandon Fujii 1K

101.325 is the conversion of kPa to atm (101.325 kPa = 1 atm). 1 Joule = 1 Pa * m3 Work = Pressure * Volume For irreversible expansion W=-P ex * Delta V For this system, we would use 101.325 kPa to convert our units from atm to Pa. (Then we would convert our liters to cubic meters) Ex 8.11: w= -(1.0...

Brandon Fujii 1K

101.325 is the conversion of kPa to atm (101.325 kPa = 1 atm).

1 Joule = 1 Pa*m³

1.20 L = 1.2x10^-3m³

Therefore, w= -(101325 Pa)(1.2x10^-3m³) = -122J

Brandon Fujii 1K

Work = -Pressure external * Delta V When Delta V is positive, the system expands. This means that the work done on the system is negative (system is doing work on surroundings). When Delta V is negative, the system compresses. This means that the work done on the system is positive (surroundings doi...

Brandon Fujii 1K

Take the vaporization of water as an example. When we boil water at 100C= 373K the heat source provides energy to break the water molecules' bonds instead of heating up the temperature of the water. Thus, the temperature of the water remains the same during a phase change.

Brandon Fujii 1K

We use 298K for the standard temperature for thermodynamics because 298K = 25C which is room temperature

Brandon Fujii 1K

In 8.57 each individual enthalpy value is given in kJ/mol. Thus, I believe that the question is asking us to solve for the enthalpy for the hydrogenation of 1 mole of ethane. 8.61 gives each individual enthalpy value in kJ (possibly because it is not solving for the enthalpy of 1 mole of Bromide Gas...

Brandon Fujii 1K

If we are given a coordination compound, i.e. [HgF₂(OH₂₎)₂]¹⁺, do we use the total charge of the compound (1+) to find the formal charge of the lewis structure in addition to finding the oxidation state of the metal atom?

Brandon Fujii 1K

PO 4 3- has a resonance structure which creates a uniform negative polar charge around the Phosphate (in a tetrahedral). Because the negative polar charge and strength of each Oxygen is equal, the charges cancel each other out and there is no dipole moment. PCl 5 is the same in the sense that each C...

Brandon Fujii 1K

Here's a table of all of the VSEPR Shapes that we need to know. I hope that this helps!

Brandon Fujii 1K

The solution manual states that the dissociation of Cl₂ is more stable than F₂ because F₂ has a larger equilibrium constant. Why does a smaller equilibrium constant make a molecule more stable?

Brandon Fujii 1K

Sorry I pasted twice, and I can't delete one of the images. I hope that the visual helps!

Brandon Fujii 1K

A tetrahedral has 4 bonds and no lone pairs.

A square planar molecular shape has an octahedral electron structure with 4 bonds and 2 lone pairs about the central atom. (see image in link)

https://image.slidesharecdn.com/10lectu ... 1381918593

Brandon Fujii 1K

For a small value of K (K< 1x10 -3 ) then the "equilibrium sits to the left" Because K=[products]/[reactants], a small K would have a large reactant concentration (left of the equation) and a small product concentration (right of the equation) at equilibrium. i.e. if K=[0.00110M]/[2.30M], ...

Brandon Fujii 1K

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj2gO_Am8bXAhXjh1QKHZevDo0QjRwIBw&url=http%3A%2F%2Fphilschatz.com%2Fchemistry-book%2Fcontents%2Fm51058.html&psig=AOvVaw06y99Sy5o2HwIBwz1IOUVH&ust=1511028916311529 We...

Brandon Fujii 1K

Hello, unless we test it experimentally, we do not know the exact angles of bonds caused by electron repulsion. Thus, we just assume that the bond angles are slightly less than 109.5 degrees for a trigonal pyramidal molecular structures.

Brandon Fujii 1K

yes for example if our velocity is 20m/s \pm 5m/s our velocity would range from 15m/s to 25m/s. Delta v is the range of the velocity. This is found subtracting the upper and lower range of the velocity (25m/s-15m/s= 10m/s ). We can use the shortcut of multiplying the velocity found after the \pm (5m...

Brandon Fujii 1K

If we were to try to add or subtract an electron from a noble gas, it would require an extensive amount of energy.

Brandon Fujii 1K

First we must find the total number of electrons in the molecule. I usually make everything a single bond first and then adjust accordingly by adding double/triple bonds if I have too many electrons (more than the calculated total number of electrons that belongs in the molecule). Then we would calc...

Brandon Fujii 1K

Also if you use number 1.45 as a practice problem, the solutions manual is incorrect. The actual velocity given is 5.00 $\pm$ 5.0m/s
Thus, $\Delta v$ =10.0m/s NOT 5.0m/s as the solution manual incorrectly states. Therefore, your answer is $\Delta x$ =6.7x10^-37m

Brandon Fujii 1K

Some examples of molecules that use covalent bonds are

Bromine (Br₂)
Iodine (I₂)
Nitrogen (N₂)
Chlorine (Cl₂)
Hydrogen (H₂)
Oxygen (O₂)
Fluorine (F₂)

Carbon Dioxide (CO₂)
Methane (CH₄)
Water (H₂O)

Brandon Fujii 1K

Electronegativity is an atom's numerical value which measures its ability to form a covalent bond. Electron affinity is the amount of energy that an atom releases when an electron is added to it. Additionally, Electron affinity is a given value for each atom, but electronegativity varies based on di...

Brandon Fujii 1K

We assume that n=1 because this is a Lyman Series, and the lowest possible energy level is n=1.

For Balmer, the lowest energy level is n=2
For Paschen n=3
For Brackett n=4
For Pfund n=5

Brandon Fujii 1K

Also, know which types of wavelengths correspond to higher or lower frequency.

i.e. x-rays have short wavelengths and therefore have a higher frequency than radio waves which have long wavelengths.

Brandon Fujii 1K

Yes, for the mass of an electron use kg

Equation: E_(kinetic)=(1/2)m_e-(v_e-)²

Units: Joules = kg (m²/s²)

Brandon Fujii 1K

Note the Photoelectric Effect equation: E (Photon) - Work Function = E (Kinetic) . E (Kinetic) = 1/2 (m e- v e- 2 ) The equation for E (Photon) = h v (Plank's Constant * Frequency) We know that the equation for the speed of light is: C= Wavelength * Frequency. Therefo...

Brandon Fujii 1K

In addition, if we have to convert our calculated number of moles into grams, do not round off the number of moles. We only round to our number of significant figures at the very end of the problem. i.e. Say we are limited to 3 sig figs, and we calculated 3.45654 moles of Oxygen gas. We would multip...

Brandon Fujii 1K

In addition, Oxygen must be present in order for a combustion reaction to occur. In most cases, Oxygen is in excess because it is found in the atmosphere. i.e. When we burn Butane in an outdoor barbecue, we have an excess Oxygen.

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