CHEMISTRY COMMUNITY

Britney Pheng 1L

Hi!

AgBr is essentially telling you that you have Ag+; you're just including the Br- with it (these two combine to be AgBr) because that was how it was given in the equation. So you could replace AgBr with Ag+. Hope this helps!

Britney Pheng 1L

Hi Sanjay!

If you count the carbons of the cyclohexane counterclockwise from the double bond, you should get the methoxy attached to the 4th carbon. :)

Britney Pheng 1L

Hi Michael! It is an electrophilic addition reaction because step 1 involves the addition of an electrophile (which in this case is H^+) to the other molecule in the first step. For general electrophilic addition reactions, a pi (double) bond is broken and two sigma (single) bonds are formed. The bo...

Britney Pheng 1L

Hi! You would use the equation ln \frac{k_{2}}{k_{1}} =\frac{E_{a}}{R}*[\frac{1}{T}_{1}-\frac{1}{T_{2}}] , which can be derived by subtracting the Arrhenius equation for temperature 1 from the Arrhenius equation for temperature 2 (this eliminates A). For reference, see page 642 in the textbook! Hope...

Britney Pheng 1L

OH- is a catalyst because it is already in the basic solution from the beginning of Step 1 (so it is not formed during the reaction). It still cancels out, meaning it is not consumed and can be used repeatedly.

Britney Pheng 1L

Hi Angela! I think this has to do with the difference between instantaneous rate of change and average rate of change. The line tangent to the curve is the instantaneous rate. It is more accurate because it's exactly one point on the curve, and delta t is practically 0. If you take the average of th...

Britney Pheng 1L

Hi Olivia! Pretty sure that's a typo in the book and it's supposed to be 14H+. In regards to how you get 8H+ in the end, you have to multiply part b) by 3 to get the same amount of electrons for both half-reactions before you can add them. This means you will have 6H+ on the products side, and 14H+ ...

Britney Pheng 1L

Britney Pheng 1L

Hi!
My TA explained that entropy in the entire universe is always increasing, and ΔSsurr would have to take that into account.

Britney Pheng 1L

Hello! I think your lewis structure for CH3CH(OH)CH3 is a bit off. The structure should have a total of 26 e-. The lewis structure that gives you a formation of a C=O bond will only have a total of 24 electrons, whereas if you attach the oxygen atom to only one carbon atom, you will get all 26 elect...

Britney Pheng 1L

Britney Pheng 1L

Hi! Neutralization occurs at the stoichiometric point. For this titration, the stoichiometric point is where the moles of H^{+} of the added titrant (HCl) is equal to the moles of OH^{-} of the analyte (NaOH). Basically, we want to get the amount of moles of HCl = the amount of moles of NaOH. Just t...

Britney Pheng 1L

Hello! Since we didn't have to draw VESPR structures for the midterm, I don't think it will be on the final. I think all we need to know is how to identify the VSEPR formula, molecular shape, etc. However, drawing out the VESPR structures may help you identify the bond angles and the molecular shape...

Britney Pheng 1L

Hi!

I think because the ratio of $H_{3}O^{+}$ ions and $OH^{-}$ ions is 1:1 in the chemical equation: $2H_{2}O (l)\rightleftharpoons H_{3}O^{+}(aq)+ OH^{-}(aq)$ and because the conditions for both ions are the exact same, they must have the same molarity.

Britney Pheng 1L

Increasing pressure (by decreasing the volume) will make your chemical equation favor the side with less gas particles. Fall 2015 Question 10 So in this problem, you only need to look at the gas molecules ( I_{2} is a solid). After you balance the chemical equation, you get: 2HCl (g) + I_{2}...

Britney Pheng 1L

michaeljwilson3 wrote:if there is a double or triple bond, that only counts as one electron density correct?

Yes, double and triple bonds only count as one electron density!

For example, $H-C\equiv N:$ would only have two regions of electron densities.

Britney Pheng 1L

Hey Karla! For the second part (hybridization of atoms), you want to count the regions of electron density of each atom, which will be equivalent to how many hybrid orbitals that atom has. In this case, both B and N have the same amount of hybrid orbitals. Each bond and lone pair of an atom counts a...

Britney Pheng 1L

Hi Erik! To add on to what Eljie said: The trends of ionization energy, electron affinity, and electronegativity on the periodic table are the same. From left to right AND down to up on the table, the elements will have an increase in these trends. So if the ionization energy of an atom is high, the...

Britney Pheng 1L

Hi Julianne, After a quick online search, I think it’s safe to say the only requirement needed to determine that an ion has resonance is that it has more than one Lewis Dot structure (that is, the ion/molecule cannot be expressed by only one structure). I found this web page that explains resonance ...

Britney Pheng 1L

Hi Parsia, Sorry for the late reply! In this question, you are given two compounds that react together to form two new compounds. This is called a double replacement/displacement reaction : AB + XY \rightarrow XB + AY The products are formed when the two cations (or two anions) of the reactants swit...

Britney Pheng 1L

Hi Michelle! What I do first is write out the complete equation: Cu(NO_{3})_{2} (aq) + 2 NaOH (aq) \rightarrow Cu(OH)_{2} (s) + 2 NaNO_{3} (aq) (We get 2 NaNO_{3} from the other products in the chemical reaction) Next, we want to write out the complete...

Britney Pheng 1L

Hi Ashley! To set up this problem you want to use the Molarity equation: \mathit{M} = \frac{\mathit{n}}{V} (Molarity = moles of solute/Liters of solution). We are given the Molarity ( 2 M NaOH) and the volume ( .3 L ) and we must solve for the moles of solute (NaOH). \mathit{2 M} = \frac{\mathit{n}}...

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