sapling 17 & 18

(Polar molecules, Non-polar molecules, etc.)

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Giselle_zamora_1L
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sapling 17 & 18

Postby Giselle_zamora_1L » Sun Nov 29, 2020 10:22 pm

Hey, I am stuck on the drawing portions of these problems in Sapling. I understand the other parts of the questions and got them right, which makes me think I understand the overall properties and have a general understanding but I can't seem to figure out the structures according to Sapling. Any tips?

Sondia Luong 1C
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Re: sapling 17 & 18

Postby Sondia Luong 1C » Sun Nov 29, 2020 10:26 pm

Hi! Generally, it's a good idea to first count all the total electrons present in the molecule. Then, find the atom with the lowest electronegativity and put it as your center atom. I like to connect the rest of the atoms to the central one with one bond, then figure out if there needs to be lone pairs or double bonds based on the number of electrons that are left and the formal charge. Hope this helps:)

Jason Nguyen_1B
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Joined: Wed Sep 30, 2020 9:34 pm

Re: sapling 17 & 18

Postby Jason Nguyen_1B » Sun Nov 29, 2020 10:27 pm

Hi! For question 17 there are 3 structures for C3H4 you have to draw. One of the structures has a C-C double bond. The other has a C-C triple bond. And the last has a C-C double bond but in a ring shape (the three carbons are formed in a triangle). For question 18, the C-C bonds for all 3 structures has a double bond. Hope that helps!

Callan Howard
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Re: sapling 17 & 18

Postby Callan Howard » Sun Nov 29, 2020 10:29 pm

Hi! I second what Jason said. The ring shaped Carbons really tripped me up, but I got it eventually, haha

Katherine_Douglas_1F
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Re: sapling 17 & 18

Postby Katherine_Douglas_1F » Sun Nov 29, 2020 10:33 pm

Hi! Drawing the structures was a little bit harder since sapling was looking for something in particular. As a general rule I would say just play around with the different bond types. First, calculate the number of valence electrons in the molecule. Then, try and form an octet for each atom. After that, calculate the formal charge to match them up. Some are easy to see after a while. For example, O has a formal charge of 0 when it has 2 bonded pairs and 2 lone pairs. C likes to have 4 bonded pairs. Generally, the more electronegative atom goes in the middle and I've noticed H atoms are usually on the outside (since they can only form 1 bond).

Hasan Mirza 3F
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Re: sapling 17 & 18

Postby Hasan Mirza 3F » Sun Nov 29, 2020 10:47 pm

For organic molecules like in #18, the chemical formulas are written to help you know the location of each atom. For problems like #17 just try to fill the octet of each atom and try using double bonds to help.

nayha a 1E
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Re: sapling 17 & 18

Postby nayha a 1E » Sun Nov 29, 2020 10:50 pm

Hi! I was stuck on #17 as well. One of the structures will have the C's connected in a ring shape. As for 18, each structure has a similar shape except that the chain of C's gets longer. They each have a double bond as well. Hope this helps!


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