CHEMISTRY COMMUNITY

Helen Mejia 1I

work being done on the system is positive while work being done by the system is negative.

Helen Mejia 1I

yes it is equal to zero.

Helen Mejia 1I

Can someone help me on how to solve problem 7D.5? It says "The rate constant of the reaction between CO 2 and OH- in aqueous solution to give HCO 3 - ion is 1.5 x 10^10 Lmol-1s-1 at 25 Celsius. Determine the rate constant at human body temperature (37 Celsius) given that the activation energy f...

Helen Mejia 1I

Always remember that the goal is to have a positive E naught because a positive value indicates that it is spontaneous.

Helen Mejia 1I

How can you rank elements by increasing reducing power?

Helen Mejia 1I

Helen Mejia 1I

When do you add Pt to the voltaic cell? Are there some conditions to memorize? Are there some special conditions that we need to remember?

Helen Mejia 1I

For acidic solutions, you add H20 to balance the oxygens and then you add H+ to balance the hydrogens. Then you should balance the charges.

Helen Mejia 1I

The oxidizing agent helps a substance get oxidized. It accepts an electron.
The reducing agent helps a substance get reduced. It gives an electron

Helen Mejia 1I

What does it mean when delta G is equal to zero? Does it have to do something with the amount of work the reaction can do?

Helen Mejia 1I

Why is that standard delta G is not measured directly unlike heat in a calorimeter to measure standard delta H?

Helen Mejia 1I

When you calculate Gibbs free energy using enthalpy and entropy in cal will our final units for Gibbs free energy be cal per mole or just cal?

Helen Mejia 1I

What are some conditions that allow delta G to be negative?

Helen Mejia 1I

Can someone explain why temperature is dependent on K in the Van't Hoff Equation?

Helen Mejia 1I

Can someone explain how to do 6d?

Helen Mejia 1I

Can someone explain the conditions when the change internal energy is equal to the change of enthalpy?

Helen Mejia 1I

Can someone explain how to identify which of BF₃ or COF₂ will have a higher molar entropy?

Helen Mejia 1I

I need help on worksheet #4 (First Law of Thermo). On the answer key, it said -631 kJ, but I got -631J. What is the correct unit? The given information is in J.

Helen Mejia 1I

I think we do continue on Thermochemistry because he just started to lecture on thermodynamics.

Helen Mejia 1I

Can someone explain how after a while the temperature of metal and water can have the same temperature after a while? If one is absorbing while the other is losing heat?

Helen Mejia 1I

Are we supposed to memorize the Heat curve or will we be given the heat curve?

Helen Mejia 1I

Since there are 3 methods can we use any in all the problems? Or is there a method that is more accurate than the other two depending on the question being asked?

Helen Mejia 1I

For an element, it is the most stable at 1 atm and the temp of interest is usually 25 celsius

Helen Mejia 1I

Can someone please explain why is the bond enthalpies the least accurate method?

Helen Mejia 1I

Thank you!

Helen Mejia 1I

Thank you!

Helen Mejia 1I

Using the formula we were given K_a x K_b= K_w will be the best thing to do.

Helen Mejia 1I

6B.9 is asking to complete a table where the concentration of H 3 O + is equal to 1.50. In the table, it is asking for the pH. I have gotten a negative answer. I get -.176 but in the solution manual it says that the pH is positive .176 Can someone please explain what happens to the negative. I have ...

Helen Mejia 1I

Can someone please explain why the concentration of H₃O⁺ equals the concentration of OH_-?
I am referring to question 6A.21. This question is asking what is the concentration of H₃O⁺ ions at 37 C. Kw= 2.1 x 10^-14

Helen Mejia 1I

Can someone explain why intermediate values of K result to neither the products or reactants are not strongly favored at equilibrium?

Helen Mejia 1I

When is it okay to use parathesis or brackets when solving for K? What is the difference between them?

Helen Mejia 1I

I second this!! Also, how did you figure out part a and b? How do we determine equilibrium by looking at the molecules? For part a, you will see that the diatomic molecules are decreasing. It goes from 11 to 8 to 5. It has reached equilibrium in flask #3 because in flask #4 it has the same amount o...

Helen Mejia 1I

Can someone explain the difference between Bronsted and Lewis acids and bases? Is there any easy way to identify what it is in an equation?

Helen Mejia 1I

Hi I am so confused about conjugate acids and bases? Can someone explain it and provide an example?

Helen Mejia 1I

I don't understand the biological importance of hemoglobin and how it is formed?
Can someone please explain it.

Helen Mejia 1I

For the problem, J.17, it says " in each of the following salts, either the cation or anion is a weak acid or a weak base in water. Write the chemical equation for the proton transfer reaction of this cation or anion with water: (a) NaC 6 H 5 O How do you start this problem? I saw the solution ...

Helen Mejia 1I

How can we determine if a ligand is polydentate? Can we tell by drawing the Lewis structure?

Helen Mejia 1I

haleyervin7 wrote:Will we be expected to memorize the names of several ligands according to the naming convention?

Yes, we are expected to know the names of the ligands. The professor has a chart that will help us to memorize the name of a ligand. The chart is in the class website.

Helen Mejia 1I

Memorizing the chart that he provides on the website is very helpful. I do not think we are given a chart to help us out. Most of the exercises on the textbook expect us to know the names already.

Helen Mejia 1I

The A in the VSEPR formula stands for the central atom.

Helen Mejia 1I

Also can someone please explain by giving an example?

Helen Mejia 1I

How does hybridization arise from atomic orbitals?

Helen Mejia 1I

For the Test do we have to put the exact bond angle when it is slightly less?
For example for AX₃E it is slightly less than 109.5, it is 107. For the Test do have to put that the bond angle is 107 or is it okay to say it is slightly less than 109.5.

Helen Mejia 1I

For test #3, can we draw the Lewis structure symmetrically? Or do we need to draw the Lewis structure as it would look with its molecular shape? For example, in class, the professor drew the Lewis structure for SF 4 and he put the fluorines all in the right side of Sulfur and the lone pair in the le...

Helen Mejia 1I

Can someone please explain pi bonds?
And also why double bonds have one sigma bond and one pi bond

Helen Mejia 1I

Can someone explain why polarizability depends on the number of electrons and the size of the atom?

Helen Mejia 1I

Hydrogen bonding is a dipole-dipole bonding. It interacts with N,O,F atoms.

Helen Mejia 1I

Hi can someone explain dipole and induced dipole?

Helen Mejia 1I

okay, thank you!

Helen Mejia 1I

Hi, can someone explain how does the speed of the ejected electron in part (a) change when the intensity of the light is increased?

Helen Mejia 1I

Hi, can someone help me on question 2 on the midterm? My T.A. tried to explain it but they only said to change km to m. Question 2: The uncertainty in the momentum of a cricket ball which is traveling at 150 m/hour is 2x 10^-6 times its momentum. Its mass is .160kg. Calculate its minimum uncertainty...

Helen Mejia 1I

Yes it does relate with the shape of orbital.

Helen Mejia 1I

So memorize that
s= 0 nodal planes
p=1 nodal planes
d= 2 nodal planes
f= 3 nodal pleanes

Helen Mejia 1I

You need to find the energy of the photon in order to find the wavelength.
The formula to find the energy of a photon is the work function plus kinetic energy.
Work function is 1.66 x 10^-17 J a
Kinectic Energy: 1/2(m)(v^2)

Helen Mejia 1I

What does it mean for an electron configuration to be in ground state? Can someone give an example?

Helen Mejia 1I

Hi, can someone please explain multi-electron atoms and electrostatic (coulomb) potential energy?
I did not understand today's lecture at all.

Helen Mejia 1I

So there is two values for m_s which are -1/2 and 1/2. If it is negative then the electron will spin down and if it is positive it will spin up.

Helen Mejia 1I

What is the exact reason that the car does not have any wavelength properties even though it is moving? The car does not have any wavelength properties because the wavelength was too small. The professor mentioned how it was even smaller than the gamma rays. I think he said that the smallest wavelen...

Helen Mejia 1I

I recall that the professor said that the smallest wavelength is 10^-18. Anything smaller such as 10^-38 is too small to be detected

Helen Mejia 1I

Hi confused why a number (4.09x10^-19J) that is negative was used as positive in a further step. Why did it change from negative to positive? The professor gave an example that said, "Calculate the frequency of light emitted by a hydrogen atom when an electron makes a transition from the fourth...

Helen Mejia 1I

Hi can someone explain how to do G5 (edition 7) It says " A student prepared a solution of sodium carbonate by adding 2.111g of the solid to a 250.0 mL volumetric flask and adding water to the mark. Some of this solution was transferred to a buret. What volume of solution should the student tra...

Helen Mejia 1I

Lynsea_Southwick_3F wrote:
Helen Mejia 3F wrote:Hey, so consider using Avogadros number (6.022 x 10^23) and multiplying it by twice the radius (which would be 288 pm).

6.022 x 10^23) Ag x (288 pm x 10^-12)= 1.73 x 10^14

Why do you multiply the radius twice?

Because you need to know how long the fiber will be.

Helen Mejia 1I

So you are given 1.00 mol of Ag, but what you are supposed to find is the number of Ag atoms from this given info. because only then can you use the radius given (144pm) to figure out how long the fiber is. Step 1: you would convert the mol of Ag to number of Ag atoms 1.00 mol Ag x (6.0221x10^23)/m...

Helen Mejia 1I

Hey, so consider using Avogadros number (6.022 x 10^23) and multiplying it by twice the radius (which would be 288 pm).

6.022 x 10^23) Ag x (288 pm x 10^-12)= 1.73 x 10^14

Helen Mejia 1I

Thank you! I see the mistake I did! I think the answer you got is correct since it was one of the options! (:

Helen Mejia 1I

Hi, I am having trouble with question 19 from the molarity post-assessment. The question says, calculate the volume of a 0.06 M sodium chloride solution containing 0.03 moles of sodium chloride. What I did to solve this was using the molarity formula. Molarity (M)= moles (n)/ volume(v). since it was...

Helen Mejia 1I

Hi Cecilia, for the readings for Chem, I am reading based on what the lectures are going to be about. For example, you can look at the lecture outlines he provided online. I am guessing that the lecture outline #1 is for week one and so on.

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