CHEMISTRY COMMUNITY

Selena Quispe 2I

Hi! So remember that [H3O+][OH-]=Kw. You are given hydronium concentrations. In order to find the concentration of hydroxide you divide 3.1 mol/L from your kw (1.00*10^-14). Your answer should be 3.2*10^-15 mol/L. I hope this helps!

Selena Quispe 2I

Hi! I don't think you would need to use PV= nRT. You would look at the Table and find that your Kc is 160 and then input the concentrations of [HI] and [I2] in the equilibrium constant equation to solve for x which is [H2].

Selena Quispe 2I

Ka is the equilibrium constant for acids and acids produce hydronium and remember pH is -log(H3O+). If you leave Kb then you would find the concentration of your hydroxide reactant and then convert to pOH and then subtract your pOH from 14 to find your pH. I believe just changing the kb to ka is jus...

Selena Quispe 2I

Yes! You answered this question correctly! I think we need the ka values to solve for pH as when you use the ka we are finding the concentration of hydronium which is needed when calculating the pH (-log[H3O+]). I hope this helps!

Selena Quispe 2I

Hi! So number 5 is a little tricky as you are only given the pH and Kb but not the initial concentration. You start by first subtracting the pH from 14 to find your pOH then do 10^-pOH to get your concentration of OH-. Then you need to find your initial concentration of B so you know that your x is ...

Selena Quispe 2I

You would need the ka and kb values to find the pH so what I did was I referred back to the tables in 6C and 6D. Sometimes you would be given the pKa or pKb but to get the ka you would just set the pka to 10^-pka. I hope this helps!

Selena Quispe 2I

They are getting the pH by either finding the pKa or the Ka from the tables in 6C or 6D. They then set there ice table and continue solving for x. If you like I can post my calculations if you want a visual of how to solve for x and find the pH.

Selena Quispe 2I

The equilibrium constant has to be smaller than 10^-3 in order for the x to be negligible. But try to double check by using the 5 percent rule!! Which is when your x has to be less than 5 percent of your initial concentration!!

Selena Quispe 2I

You solved for the X but now you have to enter 0.07 to the E in your ice table.
[PCl3]: 6-0.071 = 5.929
[Cl2]: 1-0.071 = 0.929
[PCl5]: 3 + 0.071 = 3.071

Selena Quispe 2I

Okay! I tried doing that, but I still got the incorrect concentration for SO3. I'm sorry for the late response bur your x in the end should equal to about 4.94*10^-6 so to find the concentration of SO3 you would multiply that by 2 since there are two moles of SO3 in the reaction. Your SO3 in the en...

Selena Quispe 2I

You would use the Kw given in the problem because you only use neutral water's Kw when the temperature is at 25 degrees Celsius. To find the concentrations for hydronium and hydroxide you would take the square root of the given Kw.

Selena Quispe 2I

Hi! I think you read the question wrong because it says 2HD (g) ⇌ H2 (g) + D2(g). So there will be no change because there are two moles on the reactants and two moles on the products.

Selena Quispe 2I

Hi! You would not use ammonium carbamate at all! And yes you would convert 17.4 mg of CO2 to moles of CO2 and then divide by liters to get your molarity. When making your ice table you should note that CO2 would be +x and NH3 would be +2x (2 because of the coefficient of NH3). So, because the Molari...

Selena Quispe 2I

For part b you replace Cl with F. Your reaction should be F2(g) 2F(g). The molarity for F2 is the same as the molarity for Cl2 (1*10^-3). You then set up your ice table: F2(g). 2F(g) I. 1*10^-3. 0 C. -x. +2x E (1*10^-3 -x). 2x Then set your equilibrium constant equation 1.2*10-4 (K) = (2x)^2/(1*10^-...

Selena Quispe 2I

In the beginning of the module post-assessment they had a for SO2 b for O2 and c for SO3. These are not variables we have to solve. Just multiply two times your x value to find the concentration of SO3.

Selena Quispe 2I

You know x is small because of the equilibrium constant. If the equilibrium constant is small (less than 10^-3) then the x must be very small. If we subtract a very small x then we will approximate the term to essentially stay the same. I hope this helps!!

Selena Quispe 2I

Hi! A forward reaction is when the reactants are forming products and the reverse reaction is when products form reactants. For a reaction to "favor" or "lie" or "shift" towards products it means the products are the most stable and will proceed towards it (also known a...

Selena Quispe 2I

Pertaining to a comment above, how does one go about using the reverse reaction to solve. Have we learned that in lecture and when do you know that it is okay to do this? They gave an equilibrium constant so to do the reverse reaction you would solve 1/K. Then switch the reaction to the reverse: PC...

Selena Quispe 2I

Pertaining to a comment above, how does one go about using the reverse reaction to solve. Have we learned that in lecture and when do you know that it is okay to do this? They gave an equilibrium constant so to do the reverse reaction you would solve 1/K. Then switch the reaction to the reverse: PC...

Selena Quispe 2I

I believe those assignments are optional just focus on the weekly sapling assignments, he usually has the sapling assignment that is assigned for the week on ccle :)

Selena Quispe 2I

A coordination compound can have multiple type of ligands so for example Myoglobin can have 4 NH3 and an oxygen and an amino acid (pyridine).

Selena Quispe 2I

So Cl does not have a subscript of three because the sulfato has a charge of -2 and the chlorine has a charge of -1 making it have an overall charge of -3 but the oxidation state of Cobalt (+3) cancels the charges out. For part c NH3 does not have a charge and neither does water so the bromine has t...

Selena Quispe 2I

If the pH is lower than the pka then it will be neutral, this is because the solution is more acidic than the actual acidity of the weak acid. Therefore, the acid will protonate and keep its proton. If the pH is bigger than the pKa, the solution is more basic so the weak acid will deprotonate and g...

Selena Quispe 2I

A bond is polar if there is an unequal share of electrons, causing a dipole moment. Just look at which element is more electronegative and you can infer that one end will have a partial positive charge and the other end will have partial negative charge! Attached below is an example! I hope this hel...

Selena Quispe 2I

Yes lone pairs do affect hybridization. For example if your Oxygen has three lone pairs and one bonding pair then your hybridization would be sp3. Attached below are more examples! I hope this helps and good luck studying!!

Selena Quispe 2I

If the pH is lower than the pka then it will be neutral, this is because the solution is more acidic than the actual acidity of the weak acid. Therefore, the acid will protonate and keep its proton. If the pH is bigger than the pKa, the solution is more basic so the weak acid will deprotonate and gi...

Selena Quispe 2I

Hi! So the strength of a bond can be measured by its dissociation energy so the stronger the bond the greater the dissociation energy. Also bond strength increases as multiplicity increases, which is single, double, and tripe bonds. A triple is stronger than a double which is stronger than a single....

Selena Quispe 2I

Hi! So bond angles vary so although AX3E has four regions of electron density, and has an electron arrangement of tetrahedral it's molecular shape is trigonal pyramidal so the bond angles would not be 109.5 (bond angle for tetrahedral) because the lone pair has higher repulsion and pushes the bonded...

Selena Quispe 2I

Either is correct but I believe OH2 is preferred as the Oxygen is the atom bonding with the central metal atom.

Selena Quispe 2I

The coordination number would be 4 because the en is bidentate and can form two bonds and the two chlorines form two bonds so you will have a total of 4 bonds, giving you a coordination number of 4.

Selena Quispe 2I

The coordination number would be 6 because you have 5 ammine ligands and 1 sulfato ligand bonded to the central metal atom.

Selena Quispe 2I

Cyano and cyanido are the same thing. Cyanido is the New IUPAC Name convention but either one is correct :)

Selena Quispe 2I

Ligands are inside the brackets/coordination sphere. For example, in [AlCl4]-, the ligands are the chlorines so there would be four ligands bonded to the central atom and as a result your coordination number would be 4. A great way to identify these ligands is by memorizing the sheet Lavelle has on ...

Selena Quispe 2I

You can determine the coordination number by counting the number of bonds connected to the metal central atom (the ligands inside the brackets). In this case the coordination number of this molecule would be 6 because there are four ammine ligands and 2 Bromines in the brackets which means the ligan...

Selena Quispe 2I

The charge for Cobalt is +3 because there are three chlorines which all have a -1 charge and the three NH3 do not have a charge. Therefore, to balance the charge you would need Cobalt to have a +3 charge. I hope this helps!

Selena Quispe 2I

To determine the coordination number of a coordinate compound you count the bonds connected to the central atom. For example the coordination number in [Fe(CN)6] is 6 as there are 6 ligands connected to the central transition metal atom. I hope this helps! Thank you, this makes a lot of sense! For ...

Selena Quispe 2I

You can tell if a ligand is polydentate if it has 2 or more binding sites. A great example of this is ethylenediamine which has two binding sites at the Nitrogens, it is considered to be bidentate! Another example is diethylenetriamine which has three binding sites as the molecule has three nitrogen...

Selena Quispe 2I

To determine the coordination number of a coordinate compound you count the bonds connected to the central atom. For example the coordination number in [Fe(CN)6] is 6 as there are 6 ligands connected to the central transition metal atom. I hope this helps!

Selena Quispe 2I

I don't think he mentioned all of the strong acids yet but there a total of 7 strong acids:
Hydrochloric acid (HCl), Hydrobromic acid (HBr), Hydroiodic acid (HI), Perchloric acid (HClO4), Nitric acid (HNO3), Periodic acid (HIO4), Sulfuric Acid (H2SO4), Chloric Acid (HClO3)

Selena Quispe 2I

Hi! So a molecule can be linear and have lone pairs. A great example is I3- it has five domains of electron density, 2 bond pairs, 3 lone pairs, and has a linear shape (180 degrees bond angles). I hope this helps!!

Selena Quispe 2I

Hi! So the longer the bond (weaker bonds) = stronger acids. For a strong acid you want the bond to break easily so it can easily give off its proton. And in HBr the Bromine is much bigger than the chlorine in HCl therefore the bond would be longer (weaker bond) and is a much stronger acid than HCl. ...

Selena Quispe 2I

Hi! So I like to calculate how many valence electrons I should have and then count the electrons again to make sure that I have drawn the lewis structure correctly. Also calculate the formal charges and remember you want the most stable/less charged structure. However, if you do have a charge like l...

Selena Quispe 2I

Hi! So remember that Carbon has four valence electrons and since it is not in the third period it cannot form an expanded octet, it will form four bonds. Therefore, you would have three hydrogens bonded to it and then bond oxygen and bond that oxygen with hydrogen, forming a hydroxyl group. I hope t...

Selena Quispe 2I

Isoelectronic is when atoms and ions have the same number of electrons. However, this does not imply they have the same chemical or physical properties because they have different nuclear charges. I hope this helps!!

Selena Quispe 2I

You determine the shape by the atoms bonded and not lone pairs. However if you have 4 regions of electron density and three atoms bonded and 1 lone pairs the shape would not be trigonal planar but it would be trigonal pyramidal. I would suggest memorizing AXnEn because the VSEPR formula determines t...

Selena Quispe 2I

Hi! This worksheet is pretty helpful!
https://www.angelo.edu/faculty/kboudrea ... _VSEPR.pdf

Selena Quispe 2I

Hi! So lone pairs have the greatest repulsion and they occupy a larger volume so they will push the bonding pairs down and slightly distort the bond angles by forcing the bond pairs together slightly. I hope this helps!!

Selena Quispe 2I

Hi! So bond strength increases as the multiplicity of a bond increases. In CO you have a triple bond, CO2 you have a double bond and CO32- you have a mixture of double and single bonds. Single Bonds has weaker bond strength/longer bonds than double which is also less than triple bonds. The question ...

Selena Quispe 2I

AsF3 would have a higher boiling point than AsF5 because it is a polar molecule that has Dipole-Dipole and LDF. AsF5 only experiences LDF because all of the Fluorines are pulling it equally. Could you please walk me through how you realized that AsF5 is a polar molecule? Hey! Sorry AsF3 is the pola...

Selena Quispe 2I

C and F would be more ionic because Fluorine is the most electronegative element by a lot. Fluorine has an electronegative value of 4 and Carbon has an electronegative value of 2.5 and Hydrogen has an electronegative value of 2.1. So HF would be more ionic because it has a greater electronegative di...

Selena Quispe 2I

The last one does not have dipole-dipole interactions because all of the Chlorines are pulling the Carbon equally. If you compare CCl4 to CHCl3, there is a hydrogen present that is making it dipole-dipole because there is not an equal pull as the chlorine atoms will pull the electrons to itself more...

Selena Quispe 2I

AsF3 would have a higher boiling point than AsF5 because it is a polar molecule that has Dipole-Dipole and LDF. AsF5 only experiences LDF because all of the Fluorines are pulling it equally.

Selena Quispe 2I

Expanded octets can only happen on elements in period 3 and up so if you the central atom of the lewis structure you are drawing is in period 3 or period 4, etc then it could have an expanded octet! I hope this helps :)

Selena Quispe 2I

Hi! Yes you are allowed to draw the lone pairs on the central atom. SO2 has 18 electrons and has no charge. Therefore, the Oxygens will develop a double bond with the Sulfur and have two lone pairs on it (because it needs to form an octet). You would then have two electrons left over so you will put...

Selena Quispe 2I

Hi! I believe you can look at the symmetry (if there is an unequal pull then it is polar). Also, if a molecule has lone pairs it is usually polar. For example, AsF5 is non-polar as the fluorines are pulling on the Arsenic equally. However, AsF3 is polar because there is a lone pair on Arsenic. I hop...

Selena Quispe 2I

If you go on sampling they have solutions to the textbook problems. Attached below is a pdf to the solutions in case you can't find it!

Selena Quispe 2I

Expanded octets can happen for atoms in period 3 and below. This happens when you have a full octet on the atoms in the lewis dot structure but still have left over electrons. For example, BrF3 has an expanded octet. The fluorines have a complete octet and so does bromine but there are still left ov...

Selena Quispe 2I

Hi! So the order from weakest to strongest intermolecular forces are as follows: London Dispersion Forces < Dipole-Dipole < Hydrogen Bonding < Ion-Dipole The difference between dipole-dipole and dipole-induced dipole is dipole-dipole is present with polar molecules verses dipole-induced dipole (or L...

Selena Quispe 2I

The trend for electronegativity and ionization energy generally decreases down a group and increases across the periodic table from left to right. Ionization energy is the minimum energy needed to remove an electron and as you go down a group the shells increase so the electrons are further from the...

Selena Quispe 2I

Hi! London Dispersion forces are the weakest intermolecular force. LDF is pretty much anything that interacts with each other. So hydrogen bonding has LDF, Dipole-Dipole has LDF. However, London dispersion forces are mainly in non-polar molecules. So for example, all hydrocarbons are only LDF becaus...

Selena Quispe 2I

Hi! So the inner or core electrons are the electrons from the previous noble gas in your electron configuration. Your outer electrons are your electrons in the highest energy level so you would look at the largest coefficient in your electron configuration. Lastly your valence electrons is the last ...

Selena Quispe 2I

Hi! So for the atomic radius a good way to remember the trend is thinking of a snowman. So the snowman get bigger as you go down and then imagine the snowman falling to the right. However, you should still be aware of the actual reason why the atomic radius increases going down (because energy level...

Selena Quispe 2I

Hi! For the memorization questions, I made flashcards but also made a study guide from the notes I took from the textbook and lectures. This helped me focus on the conceptuals and prevented me from getting stressed from all the notes in my notebook. Also, if you know something will be tested on like...

Selena Quispe 2I

Hi! I believe so. Lavelle said that electrons involved in resonance structures are delocalized and the real structure of that compound will have equal length bonds. In other words the real structure is the average or blending of the structures. I hope this makes sense!

Selena Quispe 2I

Hi! So because the valence electrons are being shielded by inner electrons, it reduces the effective nuclear charge. So let's say we have fluorine and are calculating the effective nuclear charge we would subtract the two inner electrons from the number of protons fluorine has. The effective nuclear...

Selena Quispe 2I

Hi! There can only be two electrons in each orbital because of the Pauli Exclusion Principle!

Selena Quispe 2I

Hi! So the textbook answer is wrong and Lavelle clarifies this through his Solution Manual Sheet on his website! You were supposed to double in this problem! I hope this helps!!

Selena Quispe 2I

Hi! Because you are trying to find the maximum number of electrons that could be ejected you would divide 6.07*10^-7 by the answer you got in part a (4.32*10^-19). I hope this helps!!

Selena Quispe 2I

Hi! So first step would be to balance your reaction! So you would put a three in front of AgCl. You identified that C6H9Cl3 was the limiting reactant so then you would multiply 0.004 mol times the moles of AgCl in the reaction which is three and then multiply by AgCl's molar mass which is 143.32g/mo...

Selena Quispe 2I

Hi! Your work is correct maybe you just messed up when calculating. I like to make sure Planck's constant is always in parenthesis so maybe try that (6.626*10^-34)/4pi=(5.2728*10^-53)/(2.73*10^-24)=2.0*10^-11m. I hope this helps!

Selena Quispe 2I

Hi! 10^-38 is to small any numbers less that 10^-15 will not be detected :)

Selena Quispe 2I

Hi! I don't think we are expected to use the equation to make the calculations of the wave function and energy. However, in Saturday's workshop with Justin he stated that we should know the conceptual aspects of Schrodinger's wave function and how squaring the wave function represents the probabilit...

Selena Quispe 2I

Hi! The modules have a lot of conceptual problems that I think could be helpful to study! Also reviewing worksheets you have completed with the the UA's can help :)

Selena Quispe 2I

Hi! Lavelle has a Solution manual error sheet on his website where he clarifies that it should be from n=3 to n=1 as energy is being emitted!

Selena Quispe 2I

Hi! I believe it depends on what the question is asking. It will sometimes tell you to solve the wavelength (nm) so you would convert meters to nanometers at the end. For the midterm I would suggest looking at your answer options and seeing if it is in nm or meters then converting if needed! I hope ...

Selena Quispe 2I

Hi! For this problem I first multiplied 0.05 nm by 0.01 and then converted it to meters to get 5*10^-13. Then used the Heisenberg's Indeterminacy Equation: delta p times delta x = h/4pi. We know that P is mass times velocity so we have (9.11*10^-31kg * delta v)(5*10^-13)=h/4pi. You then divide the d...

Selena Quispe 2I

Hi! So the energy of the incident light is equal to the sum of the kinetic energy and work function. The work function is given to you (9.83*10^-19J). So you solve for the kinetic energy which is 1/2mv^2. After plugging in your velocity into that equation you should add that plus the work function t...

Selena Quispe 2I

The Bohr Frequency Condition is if the frequency of the incoming light matches the energy difference between 2 electronic energy levels, then you will have absorption. Neils Bohr was discussing this in respect to Hydrogen. The Bohr Frequency only works for Hydrogen. I hope this helps :)

Selena Quispe 2I

Hi! So when having to do conversions I believe you have to have memorized the common SI prefixes. An example could be having to go from meter to nanometers, in every 1 nm there is 10^-9 m so that would be your conversion. I hope this helps!!

Selena Quispe 2I

In one of his video modules, Lavelle mentioned that all matter has particle and wavelike properties but only noticed for objects (like electrons) with small masses and high velocity! I hope this helps :)

Selena Quispe 2I

They are the same thing :)

Selena Quispe 2I

I believe when he says "quantized" it means that they have to have certain values like n=1, n=2, n=3, etc. There is no in between. He also mentioned that when there is conditions it is quantized meaning there is discrete variables it is not continuous like in classical mechanics. I hope th...

Selena Quispe 2I

Nitric Acid is a strong acid ( I don't know if he expects us to memorize it) but I know in AP Chem we had to memorize the 8 strong acids.

Selena Quispe 2I

Hey! So we are given the mass of Na2CO3 so we divide it by 105.991g to get the number of moles which should total to 0.02 and then we are given the volume which is 240mL but to find the molarity we need to convert mL to L so we divide it by 1000 to get Liters (0.25L). To calculate molarity you divid...

Selena Quispe 2I

In the previous questions you determined that A is the limiting reactant, so to determine the amount of product that can be produced you focus on what A can produce. You do dimensional analysis and divide 2 mol of A from 3 mol C and should get 1.5 mol C as product. Let me know if you would like me t...

Selena Quispe 2I

Hi! So you are trying to find how many moles of CO2 are produced when 1Kg of CaCO3 is used so you start first by converting Kg to g. To do this you multiply 1kg by 1000. Then you find the number of moles by dividing 100.086g of CaCO3 from 1000g and you should get a total of 9.991 mol of CaCO3. Then ...

Selena Quispe 2I

Hi! You are correct the formula for magnesium sulfate is MgS04 and then heptahydrate would be 7H20. Hepta means 7 and hydrate refers to water (H20).

Selena Quispe 2I

Hi! So you are trying to determine the mass of C in CO2 so you would divide 44.009g CO2 from 2.275g CO2 and then you would determine that in 1 mole of CO2 there is only 1 mol of Carbon and in 1 mole of Carbon there is 12.011g. You should get a total of about 0.62089g C. You would repeat this process...

Selena Quispe 2I

Hi! So you are correct!! In order to find the mass of 2-butanone you must multiply the density by 0.40mL and then to find the moles you must divide it by 72.1g. Because 2-butanone is your limiting reactant the number of moles for 3-methyl-3-hexanol will be the same number of moles you got for 2-buta...

Selena Quispe 2I

Hi! There was a typo for this problem. It should have been typed Fe3Br8 + 4Na2CO3 --> 8NaBr+ 4CO2 + Fe3O4.

Selena Quispe 2I

The number of moles would stay the same because of the Law conservation of Mass only the molarity and volume could be changed.

Selena Quispe 2I

I don't think we're expected to know the molar mass of 2-butanone or 3-methyl-3-hexanol so I simply found the molar mass from the internet. As for molar ratios a good way to think of it is the product is determined from the limiting reactant so in this case because 6.18*10^-3 mol of 2-butanone was p...

Selena Quispe 2I

Hi I thought the same way as you did! The first step would be to convert the given density for 2 butanone into grams so you would multiply the density (0.81 g/ml) by the given volume (0.55mL) to get 0.445g of 2 butanone. Then you would find the moles so divide 72.1g (the molar mass of butanone) from...

Search found 93 matches