CHEMISTRY COMMUNITY

yaosamantha4F

Is this the problem about the empirical/molecular formulas of gallic acid? After calculating the number of g of H produced through combustion using the molar mass of H2O and the molar ratio of H and H2O, you divide by H's molar mass (1.007) to find the number of moles!

yaosamantha4F

I believe carbonato is bidentate!

yaosamantha4F

I would memorize them just to be safe!

yaosamantha4F

Thank you for posting these!

yaosamantha4F

Thank you so much for these problems!

yaosamantha4F

If you get at least 250 points, you're guaranteed a C-. I believe Dr. Lavelle said he would work out the specific letter grade/point distributions after the final?

yaosamantha4F

The bond angles for a seesaw shape will be a little bit less than 90 and 120 degrees due to the lone pairs' repulsion pushing the bonds slightly.

yaosamantha4F

Single, double, and triple bonds all count as one region of electron density, so the bond type doesn't affect naming using VSEPR.

yaosamantha4F

I think it's helpful but not 100% necessary to memorize the bond angles, since you can usually determine them by visualizing the shape.

yaosamantha4F

Adding on, because sigma bonds overlap end-to-end, they allow bound atoms to rotate, while pi bonds, which overlap side-to-side, do not allow bound atoms to rotate. Sigma bonds are also formed between atoms, while pi bonds are formed above/under/beside sigma bonds.

yaosamantha4F

Thank you again for posting these worksheets!

yaosamantha4F

Electron geometry refers to how electron groups are arranged, while molecular shape how all the atoms in a molecule are arranged. Lone and bonding electron pairs are considered in electron geometry, while molecular shape only considers bonding electron pairs. For example, using electron geometry, a ...

yaosamantha4F

We just need to submit 14 problems (for both week 8 and week 9) the week after we get back from break!

yaosamantha4F

The energy between the 3d and 4s orbitals is not very big, so the d-orbitals can take in additional e- to give an expanded octet. In the first and second periods of the periodic table, no d-orbital exists, but starting with the third period, the d-orbital is present and can accomodate additional e-.

yaosamantha4F

Actual yield is calculated based off of the results of an experiment while theoretical yield is calculated based off of the complete reaction of the limiting reactant. Actual yield should be given to us in any problem that requires it since it's impossible to determine without conducting the experim...

yaosamantha4F

First, calculate the molar mass of KMnO4 (158.09g/mol). Next, concert 5g KMnO4 to moles and 150mL to L and use the formula M=mol/L to calculate the molarity of the first solution. Lastly, use the equation M1V1=M2V2 equation to calculate the concentration of the second flask by using the value you pr...

yaosamantha4F

Ionic bonds are usually formed between a metal and a nonmetal; the metal loses electrons are transferred to the nonmetal so that both atoms can have the same electron configuration as the preceding/following noble gas. Covalent bonds, on the other hand, involve electrons being shared between atoms t...

yaosamantha4F

There's also a Facebook Messenger chat that's fairly active!

yaosamantha4F

Thanks for the practice midterm problems!

yaosamantha4F

The normal ground state configuration for Ag is [Kr]4d^10 5s^1. Based off of the Aufbau principle, silver's expected configuration would be [Kr]4d^9 5s^2, but since a full or half-full subshell is more stable than a partially-filled one, the s electron is transferred to the d orbital since having th...

yaosamantha4F

He focused mainly on the differences between ionic and covalent bonds and how they each achieved the octet rule, and also demonstrated how to draw several different Lewis structures.

yaosamantha4F

Ionic radii increase in size down a group (column) since more shells means that valence electrons are further away from the nucleus and decrease across a period (row) since atoms' increased nuclear charge means that they will pull their electrons in more closely (shell contraction).

yaosamantha4F

That should be correct, although when you're plugging numbers into your calculator, make sure to put parentheses around (m*wavelength). It is not reasonable for an electron to be faster than the speed of light, but if the electron is below 10^5m/s, this may also be too slow to be reasonable.

yaosamantha4F

Both are okay to use but 2.998*10^8 m/s will give you a more accurate answer!

yaosamantha4F

Starting with 348kJ/mol, you would multiply by 348kJ/mol C-C bonds * 1mol C-C bonds/6.022*10^23 C-C bonds *1000J/kJ to ultimately end up 5.78*10^(-19)J as ΔE. You can then use the equation λ=hc/ΔE and plug in Planck's constant, the speed of light, and ΔE to get 3.44*10^-7m (or 344nm). This falls und...

yaosamantha4F

I would try to round at the very end whenever possible! Keeping more sig figs in your calculations allows you to end up with a more accurate final result.

yaosamantha4F

Your steps look right; maybe double check that you're using the right molar masses and inputting the correct numbers into your calculator?

yaosamantha4F

I would go with whatever your TA says to your discussion section; our TA specified that we would be given formulas for any chemical compounds!

yaosamantha4F

If you go ahead and balance the chemical equation first, you get B2O3 + 3Mg(s) -> 3MgO(s) + 2B(s). You then need to calculate the mass of boron that is produced from both Mg and B2O3. First, convert the masses of both from kg to g, divide by the molar mass of the compound, multiply by the ratio of B...

yaosamantha4F

The coefficients are used to represent the number of atoms/molecules on each side! With coefficients of 2, 2, 2, and 1, both sides of the reaction end up with 2 atoms of Na, 4 atoms of H, and 2 atoms of O.

yaosamantha4F

1.001 has 4 significant figures! A trick I use to remember which numbers to count as sig figs is the the Atlantic/Pacific analogy. If there's a decimal point present, start from the left (since the Pacific ocean is on the left/west coast of the US) and count starting from the first non-zero number. ...

CHEMISTRY COMMUNITY

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Re: Midterm Solutions Fall 2018-2019 year

Re: Polydentate

Re: memorizing complexes?

Re: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]

Re: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]

Re: Final Grades

Re: Seesaw

Re: double and triple bonds

Re: Naming the Shape

Re: Sigma and Pi bonds

Re: DOWNLOAD SESSION WORKSHEETS HERE - Sundays 4-6pm (Karen) [ENDORSED]

Re: Molecular Shape vs. Electron Geometry

Re: Turning in Homework (Thanksgiving Break)

Re: Atoms with 8+ valence e-

Re: Actual Yield

Re: Midterm Review Q2

Re: Ionic vs Covalent Bonds

Re: Group Me

Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]

Re: 2A.21 7th Edition Question

Re: Friday 10/26/18 lecture

Re: Trend of Ionic Radii

Re: DeBroglie Equation Post Assessment

Re: Calculating the wavelength of light

Re: Question 1.65 (Sixth Edition)

Re: When to round the answers to significant figures

Re: L.5 Part B Sixth Edition [ENDORSED]

Re: Chemical compounds

Re: Comparing Calculated Moles step M7(b)

Re: Mole Coefficients in Chemical Equations

Re: sig figs urgent question!