CHEMISTRY COMMUNITY

Chloe Shamtob 2H

In the cathode of a galvanic cell, reduction occurs and at the anode oxidation occurs.

Chloe Shamtob 2H

Yes, the anode is always oxidizing and the cathode is always reducing.

Chloe Shamtob 2H

Bond enthalpies are given to you in the chart. Also remember that bond enthalpies are always positive

Chloe Shamtob 2H

You add pt to the sides with no conducting metal. Mg is also an exception and can conduct even though it’s a liquid.

Chloe Shamtob 2H

We need degeneracy to calculate entropy and the disorder of the system.

Chloe Shamtob 2H

Yes you have the correct reasoning. The larger the value of k the faster the reaction.

Chloe Shamtob 2H

The rate of the reaction does not depend on the concentration of the reactants when considering a zero order reaction.

Chloe Shamtob 2H

You have the correct reasoning. Intermediates are produced then consumed in a reaction while catalysts continue to show up in the reactions.

Chloe Shamtob 2H

Thank you so much Dr Lavelle for an amazing quarter!! I have never learned so much chemistry in my life and had fun learning. It was great having you as my professor for the past two quarters! Also shoutout to all the UAs and TAs you guys are the best!

Chloe Shamtob 2H

I think final grades will be released in a week or so. In chem 14a, it took about a week.

Chloe Shamtob 2H

If the concentrations are the same, E will always be zero because the system is at equilibrium. Therefore Q would be equal to one and ln of 1 is zero which means E would be zero.

Chloe Shamtob 2H

I sometimes use the acronyms stated above but most of the time I just remember that when a substance is being reduced it it gaining more electrons and therefore has a lower exponent number so it literally gets "reduced". From there I just remember that oxidation is the losing of electrons....

Chloe Shamtob 2H

For this problem I wrote out the half equations for each element and used the table to find the E naught of each half reaction. From there I found the E naught of the reaction and put it into the nernst equation which also consists of Q which is found using the concentrations given.

Chloe Shamtob 2H

What range (in volts) does a voltmeter need to have to measure pH in the range of 1 to 14 at 25 °C if the voltage is zero when pH = 7?
Can someone help me begin this problem?

Chloe Shamtob 2H

A 1.0 m NiSO4(aq) solution was electrolyzed by using inert electrodes. Write (a) the cathode reaction; (b) the anode reaction. (c) With no overpotential or passivity at the electrodes, what is the minimum potential that must be supplied to the cell for the onset of electrolysis? How do you know the ...

Chloe Shamtob 2H

In lecture, Lavelle mentioned there must be a salt bridge for a redox reaction. Why must we include this salt bridge in the reaction along with the ions being oxidzied or reduced?

Chloe Shamtob 2H

After the midterm I took a long nap and ate my favorite foods. I completely took my mind off school for the rest of the day and tried to enjoy what was left of my night.

Chloe Shamtob 2H

You need to pay attention to the context f the problem when deciding the sign of work. Work will be negative if the system is doing work on the surroundings. Work is positive when the surroundings is doing work on the system (work is being done to the system).

Chloe Shamtob 2H

The units of work is usually liters atm because the w=-pdeltaV with pressure being in atm and volume in liters. Most of the time the answer is in joules so you must convert liters atm to joules using 1 L.atm= 101.325 Joules.

Chloe Shamtob 2H

An anode is where electrons are given off or released. It is where the oxidation happens. These released electrons glow toward the cathode where the reduction of another substance happens.

Chloe Shamtob 2H

Thermodynamically favorable is usually in reference to delta G or Gibbs free energy. The term means that delta g is negative so the reaction is spontaneous and the products are stable.

Chloe Shamtob 2H

For this formula, you should always convert celsius to kelvin. I have often made that mistake in the past and have got a question wrong, So make sure you convert your temperatures to kelvin.

Chloe Shamtob 2H

Which of the following compounds become less stable with respect to the elements as the temperature is raised:
(a) PCl5(g); (b) HCN(g); (c) NO(g); (d) SO2(g)?

Can someone help me with this question from the textbook? I keep getting a different answer than the solution manual.

Chloe Shamtob 2H

Enthalpy, which is denoted by H, is used to describe the amount of heat released or absorbed at a constant pressure. Entropy, which is denoted by S, is used to measure of the likelihood that the system will be in a particular state and the disorder of the particles. The more possible states a system...

Chloe Shamtob 2H

Most of the time you need to convert temperature from celsius to kelvin. Especially when you using the gas constant you should make sure to do this. I always covert to SI units to be on the safer side. The only time when its acceptable not to change the units is when your calculating the change in T...

Chloe Shamtob 2H

I used the same method as you did and got the right answer. Double check that you calculated your delta G correctly and that your units match up and cancel out.

Chloe Shamtob 2H

The textbook is using this equation to show that the heat of the calorimeter is equal to the negative heat of the surroundings. It is basically saying that the values are equal and opposite of eachother.

Chloe Shamtob 2H

First you must calculate delta G. Using delta G, you will check if the reaction is spontaneous or not. If delta G is negative the reaction is spontaneous and if delta G is positive the reverse reaction is spontaneous. Therefore, when the reaction is spontaneous it naturally forms products and when i...

Chloe Shamtob 2H

Considering positional disorder, would you expect a crystal of octahedral cis-MX2Y4 to have the same, higher, or lower residual entropy than the corresponding trans isomer? Explain your conclusion. Can someone explain why cis has 12 orientations and trans has four? It was on the answer key but I was...

Chloe Shamtob 2H

Internal energy is dependent on work and heat. The change in internal energy is equal to the amount of heat plus the amount of work. The internal energy is positive if theres work done of the system and there is heat absorbed. The internal energy is negative if the system does work on something (suc...

Chloe Shamtob 2H

The gas constant you are suppose to use always depends on your units. Make sure to write down your units when doing a problem to make sure not to mix them up. The way I do it is I look to see if the values are in L.atm or joules. This helps a lot. Make sure things cancel out in the end or you will g...

Chloe Shamtob 2H

Delta H should always be positive in endothermic reactions. Whenever a reaction is endothermic, it is gaining heat and therefore there is an increase or positive amount of heat absorbed. Therefore, the enthalpy is positive. It's the opposite for exothermic reactions. For a reaction that is exothermi...

Chloe Shamtob 2H

Yes, as said above, the equations that you have designated for reversible and irreversible are correct. You know the second step is irreversible because it usaully will tell you in the problem and differentiate between reversible/isothermal reactions and irreversible. Most of the time if it doesn't ...

Chloe Shamtob 2H

I 100% know what you mean. Careless errors always happen and the best thing to do is check over your work. Also repeat the problems a few times to make sure you get the same answer again. I would also put my full attention to what I'm writing and calculating.

Chloe Shamtob 2H

Hydrochloric acid oxidizes zinc metal in a reaction that produces hydrogen gas and chloride ions. A piece of zinc metal of mass 8.5 g is dropped into an apparatus containing 800.0 mL of 0.500 M HCl(aq). If the initial temperature of the hydrochloric acid solution is 25°C, what is the final temperatu...

Chloe Shamtob 2H

An ice cube with a mass of 54.8 g at 0.0 ∘C is added to a glass containing 414 g of water at 45.0 ∘C . Determine the final temperature of the system at equilibrium. The specific heat capacity of water, Cs , is 4.184 J/g⋅∘C , and the standard enthalpy of fusion, ΔH∘fus , of water is 6.01×103 J/mol . ...

Chloe Shamtob 2H

Taking the anti log is a very important skill to have when your dealing with acid and base concentrations and equilibrium. To take the anti log of a pka value first you must make it negative and then put that negative value to the power of 10 (10^-pka). This will give you the Ka value you are lookin...

Chloe Shamtob 2H

HCIO3 is considered to be a strong acid. It is one of the 7 strong acids you should remember. The conjugate base of this strong acid would be very weak.

Chloe Shamtob 2H

For calculations concerning with finding the Kc of a reaction you should convert the products and reactant to mol/per liter. For calculations regarding Kp you must convert the reactants or products to partial pressure in bar or atm.

Chloe Shamtob 2H

You should be familiar will this equation and be able to convert from moles to pressure easily. There were a couple homework and module questions on this so expect to see it on this exam and other future exams as well.

Chloe Shamtob 2H

It will most likely take a couple days to a week to get our scores back. For Chem 14A it took about a week so I'm expecting the same for this class.

Chloe Shamtob 2H

You would make x negligible for equilibrium problems if the Ka or Kb is 10^-4 or smaller. Therefore, the change X would be too small to be significant. Make sure that the shortcut is allowed by finding the % ionization. If the percent ionization is less than 5%, your approximation is valid.

Chloe Shamtob 2H

You would make x negligible for equilibrium problems if the Ka or Kb is 10^-4 or smaller. Therefore, the change X would be too small to be significant. Make sure that the shortcut is allowed by finding the % ionization. If the percent ionization is less than 5%, your approximation is valid.

Chloe Shamtob 2H

I feel the same way! But keep your head up there's more opportunities to do well and raise your grade. You might of not done as bad as you think. You tried your hardest and thats all that matters.

Chloe Shamtob 2H

I had Lavelle last quarter for 14A and something that really helped me study for the exams was definitely the textbook. You should go over the textbook problems several times until you know how to do them completely without any hesitation or looking back at your notes. You should also mark any probl...

Chloe Shamtob 2H

To know whether a change in equilibrium is negative or positive for the reactants, you must pay attention to the direction of the reactions. When a reaction favors the products (reactants form from product), the reactant's change (or C in the ice box) would be negative. When a reaction favors the re...

Chloe Shamtob 2H

Temperature is constant even when heat is being supplied or released during a phase change because the heat that is being added to the substance is being absorbed to break the bonds of that substance and change its phase. Therefore, because the heat is being used up to break the bonds the additional...

Chloe Shamtob 2H

To know whether a change in equilibrium is negative or positive for the reactants, you must pay attention to the direction of the reactions. When a reaction favors the products (reactants form from product), the reactant's change (or C in the ice box) would be negative. When a reaction favors the re...

Chloe Shamtob 2H

Ka and Kb are both equilibrium constants with the difference of Ka being the acidity constant and Kb is the basicity constant. They both can be solved using the equilibrium constant equation products/reactants [P]/[R] (including exponents when there are stoichiometric coefficients).

Chloe Shamtob 2H

The kb for an amine is 3.056×10−5. What percentage of the amine is protonated if the pH of a solution of the amine is 9.249 ? Assume that all OH− came from the reaction of B with H2O.

Can someone help me start this problem? Thank you!

Chloe Shamtob 2H

Rank the following solutions in order of increasing pH: a) 1.0x10^-5 M HCl, b) 0.20 M CH3NH3Cl(aq), c) 0.20 M CH3COOH(aq), d) 0.20 M C6H5NH2

The answer key in the textbook does this question without any calculations but I don't know where they are getting the pH from? Can someone explain this to me

Chloe Shamtob 2H

To figure out whether to use a ice table or the equilibrium constant equation you must pay attention to what is given in the problem. If you are given the initial concentrations of the reactants and an equilibrium concentration, you should use the ICE table to find the concentrations of the products...

Chloe Shamtob 2H

Last quarter I attended all the lectures and took notes. I also would continually look back at those notes as I was doing textbook problems. Attending UA workshops also helped me a lot. I would recommend redoing all the assigned textbook problems the week of the midterm as a refresher.

Chloe Shamtob 2H

To figure out whether you must you -x or +x you must pay attention to the given initial concentrations in the problem. When the problem gives the concentration of the initial reactant only and excludes the product, you use -x because the reactants are being used up to make the products in the reacti...

Chloe Shamtob 2H

If H2O is shown as a gas, you do not omit it from your ice table. It H2O is a liquid and is used as a solvent, you would not include it because it is in excess and the concentration of H2O does not change in the reaction.

Chloe Shamtob 2H

The value of Kw for water at body temperature (37°C) is 2.1 X 10^-14. (a)What is the molarity of H3O+ ions and the pH of neutral water at 37°C? (b) What is the molarity of OH- in neutral water at 37"C?

For this problem why do we assume that the concentrations of H3O and OH are the same?

Chloe Shamtob 2H

5J.5 State whether reactants or products will be favored by an increase in the total pressure (resulting from compression) on each of the following equilibria. If there is no change, explain why that is so. (d) 2HD(g)+H2(g)⇌D2(g) Can someone help me with this question? The answer key says there's no...

Chloe Shamtob 2H

13. State whether the equilibrium shifts towards products, reactants, or neither when the given change occurs. 2 HI(g) + Cl2(g) ⇌ 2 HCl(g) + I2(s) delta H° = -238.0 kJ.mol-1 i. The volume of the system is compressed. ii. The temperature of the system is decreased. A. i = Products, ii = Products B. i...

Chloe Shamtob 2H

29. A researcher fills a 1.00 L reaction vessel with 1.84 x 10-4 mol of BrCl gas and heats it to 500 K. At equilibrium, only 18.3 % of the BrCl gas remains. Calculate the equilibrium constant, assuming the following reaction is taking place. 2BrCl(g) ⇌ Br2 (g) + Cl2(g) A. 19.5 B. 8.39 x 10-5 C. 4.98...

Chloe Shamtob 2H

12. For a chemical reaction that has reached equilibrium which statement is false? A. The forward reaction rate is the same as the reverse reaction rate. B. No matter what combination of concentrations of reactants and products we start with, the reaction will reach equilibrium. C. There is no react...

Chloe Shamtob 2H

Yes the equation must be balanced before finding the equilibrium constant because you must use the stoichiometric coefficients in the equation for the equilibrium constant. The concentration of the reactants and products are raised to their coefficients in the equation.

Chloe Shamtob 2H

For part A I said true because when a chemical equilibrium is reached, the concentration of reactants and products stays the same so therefore the composition remains the same. For part B, I said false because speeding up the reaction does the affect the amount of concentration of reactants or produ...

Chloe Shamtob 2H

I would review my notes to help remember what we had learned and do simple problems to make sure I still remember how to do them.

Chloe Shamtob 2H

Our final grades should be up by Saturday and our week ten chemistry community post are due this Thursday at 10am

Chloe Shamtob 2H

The bong angels for a T shaped molecule are slightly less than 90 degrees because of electron repulsion of the lone pairs

Chloe Shamtob 2H

Acetonitrile, CH3CN, is used as a solvent in the pharmaceutical industry. Describe the structure of the CH3CN molecule in terms of hybrid orbitals, bond angles, and σ- and π-bonds. The N atom is a terminal atom. The answer for this questions was not in the solutions manual so I was wondering if anyo...

Chloe Shamtob 2H

HClO2 is a stronger acid than HBrO2. Doesn't the fact that Cl and Br are in the same group and the Br-O bond is longer and weaker than the Cl-O bond outweigh the greater electronegativity of the Cl bond though?

Chloe Shamtob 2H

6C.17 Which is the stronger base, the hypobromite ion, BrO−, or morphine, C17H19O3N? Justify your answer. The answer key for this question says that hypobromite is smaller because it has a smaller KPB value. How are we suppose to know what the KPB value of a base is? Can someone help me out with thi...

Chloe Shamtob 2H

The molar concentration of HCl in hydrochloric acid is reduced to 12% of its initial value by dilution. What is the difference in the pH values of the two solutions?

Can someone help me start this problem?

Chloe Shamtob 2H

When writing the formula for a coordinate compound with more than one ligand, how do you know which one to put first in the brackets?

Chloe Shamtob 2H

When writing the formula for a coordination compound, how do you know whether tow rite water as H2O or OH2. Does it matter?

Chloe Shamtob 2H

2.57 Acetonitrile, CH3CN, is used as a solvent in the pharmaceutical industry. Describe the structure of the CH3CN molecule in terms of hybrid orbitals, bond angles, and σ- and π-bonds. The N atom is a terminal atom.
Does anyone know the answer to this question? It wasn't on the answer key.

Chloe Shamtob 2H

Are terminal atoms hybridized or just central atoms?

Chloe Shamtob 2H

When a question asks to find the hybrid orbitals of an atom such as CH2O, why do we find the hybridization of C and O?

Chloe Shamtob 2H

Noting that the bond angle of an hybridized atom is 109.5° and that of an hybridized atom is 120°, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased? I'm a little confused on what this question is asking. Can someone pleas...

Chloe Shamtob 2H

To find the hybridization of the oxygen atom you must first consider the region of electron densities on the atom. By looking at the oxygen atom, you can see it that it has two bonds and two lone pairs giving it four regions of electron density. Therefore, you can conclude that the oxygen atom has a...

Chloe Shamtob 2H

How can you tell if something is a delocalized pi bond? I know pi bonds on a lewis structure are the additional bonds formed between two atoms but what exactly does a delocalized pi bond imply?

Chloe Shamtob 2H

How do you find the negative pole on a molecule? Is it just between the two atoms with the most electronegativity difference?

Chloe Shamtob 2H

What is the difference between axial and equatorial atoms in a 3-d structure? One of the sapling problems asked to identify them and I was a little confused. Can someone help me out?

Chloe Shamtob 2H

In one of the lectures, Dr. Lavelle kept mentioning how lone pairs are "more diffuse" than bonding pairs. I was a little confused on this statement. Can someone further explain what he means by this?

Chloe Shamtob 2H

A good rule of thumb is that the smaller and more highly charged a cation is the higher polarizing power it has. Polarizing power refers to the cation's ability to pull the anion's electrons into the shared/bonding region distorting them from the original anion. When looking at polarizability, large...

Chloe Shamtob 2H

I usually make a study guide for each exam. I go through the textbook and write down the main point of each section. After I grasp the content of that section, I do all textbook problems assigned to that section. I also do all of the corresponding UA worksheets and attend as many session as I can. T...

Chloe Shamtob 2H

I felt pretty good after this midterm but how you feel now is the way I felt after midterm 1. Don't worry, everything will be okay! Just study hard for the final exam!

Chloe Shamtob 2H

A coordinate covalent bond is a type of covalent bond between a Lewis acid and lewis base. The base is the donor of an electron pair and the lewis acid is the accepter of the electron pair, lacking a pair, forming a bond. A common example is between BF3 and NH3.

Chloe Shamtob 2H

Why would CF4 have more ionic character then CH4? Isn't there a bigger electronegativity difference between C and H then between C and F?

Chloe Shamtob 2H

For one of the questions in the textbook, it mentions vapor pressure. How does vapor pressure correlate with boiling point? If something has a lower boiling point does that mean they have a lower vapor pressure?

Chloe Shamtob 2H

Hi, Im confused about the topic of oxidation numbers. What are they and how do you find them? Have we learned them yet?

Chloe Shamtob 2H

We won't have more time. It will still be 56 minutes.

Chloe Shamtob 2H

3.F15 Explain for the differences in boiling points of the three molecules; CH3F, CH2F2 and CF4.? Hi, can someone help me out with this question? What makes the boiling points different?

Chloe Shamtob 2H

2D.3 Which of these compounds has bonds that are primarily ionic? (a) BBr3;(b) BaBr2;(c) BeBr2
How would you know which are primarily ionic? Can someone help me start his problem?

Chloe Shamtob 2H

2B.9 Draw the complete Lewis structure for each of the following compounds: (a) ammonium chloride; (b) potassium phosphide; (c) sodium hypochlorite. How do we figure out the subscript for each element when we are writing the formula for the compound? Also, how come we draw the lewis structure for (a...

Chloe Shamtob 2H

2A.23 On the basis of the expected charges on the monatomic ions, give the chemical formula of each of the following compounds: (a) magnesium arsenide; (b) indium(III) sulfide; (c) aluminum hydride; (d) hydrogen telluride; (e) bismuth(III) fluoride. How would you do this problem? Would this be inclu...

Chloe Shamtob 2H

Question 11: Which M3+ ions (where M is a metal) are predicted to have the following ground-state electron configurations? (a) [Ar]3d6 (b) [Ar]3d5 (c) [Kr]4d5 (d) [Kr]4d3 For this question, I'm using the periodic table and looking at what element corresponds to the electron configuration. For (a), I...

Chloe Shamtob 2H

2A.1 Give the number of valence electrons (including d electrons) for each of the following elements: (a) Sb; (b) Si; (c) Mn; (d) B.
Does anyone have an easy way to figure the number of valence electrons just from looking at the periodic table? Thank you so much for your help!

Chloe Shamtob 2H

In lecture 16, it was mentioned that if there is an electronegativity difference greater that 2 between two elements there is ionic bond and if there is an electronegativity difference less than 1.5 between two elements there is a covalent bond. What happens if there is an electronegativity differen...

Chloe Shamtob 2H

Yes you are correct. The distortion of electrons refers to the electrons being pulled into a shared space. The electrons from a larger anion will have a larger distortion and the electrons more likely to be pulled into the shared space making the ion exhibit covalent bond characteristics. The higher...

Chloe Shamtob 2H

Electronegativity is defined as the electron pulling power of an atom. It depends on both electron affinity and ionization energy. Therefore electronegativity increases across a period because elements to the right of a period are able to attract electrons more easily. Down a group, electronegativit...

Chloe Shamtob 2H

1F.19 Why are s-block metals typically more reactive than p-block metals?

Hi, can someone explain this question to me? What does it mean by more reactive?

Chloe Shamtob 2H

Can someone clarify the term isoelectronic in respect to ions? Why is it significant and is there any characteristics of isoelectronic ions I should be aware of? I was very confused on this term and it showed up throughout the homework. Please let me know if you can help!

Chloe Shamtob 2H

To find the uncertainty in velocity you would use the heisenbergs uncertainty equation delta p= h/delta x *4pi and plug in the uncertainty of position given. Then you would solve for momentum and once you have found that you could plug your momentum and the mass of an electron into the equation v=p/...

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