chapter 9 molecular geometry and bonding Flashcards

Question

How many sigma bonds are in a molecule with 4 single bonds and 2 double bonds? hint: there's a picture of a molecule but I don't even know what it is. a. 5 b. 6 c. 7 d. 8 e. 9

Answer 1

e. none of these if you draw them out, you can see that they're all symetrical and therefore, non-polar

Answer 2

b. III only I took an educated guess here and got it right. Here is the book's explanation... BF3 is trigonal planar and the 3 bond dipoles ‘cancel’ resulting in a nonpolar molecule CO2 is linear and its bond dipoles are 180˚ apart and ‘cancel’ resulting in a nonpolar molecule. CH2Cl2 is tetrahedral and has bond angles of 109.5˚ (not 90˚ and 180˚). The bond dipoles are therefore not 180˚ apart and do not completely ‘cancel’ each other making CH2Cl2 polar.

Answer 3

d. II and III This is the book's answer which isn't very good: II and III are both polar as the individual bond dipoles do NOT cancel overall. I is nonpolar as all the individual bond dipoles all cancel. Me again: So they each have 4 electron orbitals with no lone pairs but I guess, since there are different types of atoms pulling on II and III, that's what makes them polar

Answer 4

e. I, II, and III This one I could sort of intuit. NH3 has a lone pair on top so that's going to throw off the molecular geometry causing it to be polar. H2O is famously really polar because it's 'bent' And CF2H2 (I'm probably not writing that right) is polar even though the Lewis drawing makes it look like it wouldn't be. It's 4 orbitals with no lone pair BUT, they'e all at 109.5 with one orbital sprouting out the top and the rest making sort of a tripod.

Answer 5

b. III only I guessed! And I got it. After drawing them out. BCl3... Cl is the only type of atom connected to B and they're all pulling an even 120 degrees so; non-polar CF4... There are no lone pairs and all the atoms are pulling at an even 109.5 In a previous question, there was a similar one where there were two each of different types of atoms connected to the carbon and this made it polar any way you sliced it so just keep that in mind.. It was like CCl2H2 or something And lastly, NF3 has a lone pair so it's going to push on the other 3 F atoms making it polar

Answer 6

b. II only I feel like I'm getting better at these finally. It helps to use the study guide with the pictures of the molecular geometry. SeF4 has a lone pair on the Se so that's going to throw off the symetry. XeF2 is non-polar even though there are 3 lone pairs on Xe. However, the F's will pull at 180 degrees aprt and then the lone pairs, all on their own plan, will pull in perfect 3rd's of each other. IF3 has 2 lone pair but one of the F's will be on the lone pairs' plane also so that will tip things in one direction.

Answer 7

b. 2 depite the double bonds made to improve the formal charge, there are still only 2 electron domains

Answer 8

d. 4 There are 26 total electrons. Phos has 5 valence. 3(6) oxygens make 18 valence. Plus 3 extra because it's a polyatomic ion. This will leave 2 extra for one lone pair.

Answer 9

b. tetrahedral There are four domains with no lone pairs. The molecular geometry and electron domain geometry would have the same name.

Answer 10

a. bent There is one lone pair making that 3 electron domains total. Because one of the domains is a lone pair, the shape and name will be different than it would for just the electron domain geometry.

Answer 11

d. square planar There are 6 total electron domains. Two of those domains are lone pairs. Kr has 8 valence. Br has 4(7) = 28 electrons. IF! the question was asking what the electron domain geometry was, it would be octahedral so just keep that in your back pocket.

Answer 12

d. This is almost a trick question. It's asking for the electron domain geometry not the molecular geometry so the fact that there are two lone pairs doesn't make a difference in this case.

Answer 13

c. 120 I honestly don't have these memorized but who cares? I know where to quickly find it in the study guide. BCl3 has 3 electron domains with no lone pairs (B is going under the octet rule which is common for it) which makes the angles 120

Answer 14

d. 180 degrees Again, just refer to the study guide. There are 6 total electron domains, 2 of them being lone pairs. This makes the molecular geometry square planar. The 4 F's are all 90 degrees apart but the lone pairs sprout out from each vertical end like north and south so... 180

Answer 15

c. sp3 I felt like this was a trick question but... Just s isn't a hybrid orbital so, despite the other atoms being hydrogens, you're still going to need an actual hybrid because there are 4 of them. 4 obritals (excluding s1)... Just count the boxes. s2 p1 p2 p3 = sp3

Answer 16

d. sp3 There is a lone pair so there are 4 total orbitals. When you count the boxes, you'll end up in the 3rd 'p' box. So... sp3

Answer 17

d. 1 sigma and 2 pi The first bond is a sigma. Any bonds after that are pi

Answer 18

b. NH3 This is because NH3 has a lone pair which slightly warps the symmetry required for something to be considered 'non-polar'

Answer 19

d. BCl3 I guessed and got it right. It was between that and CH2Cl2 which seems like, with the central atom being carbon, the other two atoms could sprout out perpendicular to each other but that's kind of far-fetched. BCl3 is just straight up 'the Cl's are pulling it evenly into 3rds

chapter 9 molecular geometry and bonding Flashcards

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