g Of the following substances, only has London dispersion forces as its only intermolecular force. Of the following substances, only has London dispersion forces as its only intermolecular force. AsH3 HI CCl4 C4H9OH F2S

CCl4

Explanation:

Let us look at the structure of CCl4 closely in order to really determine if it is the correct answer to the question or not.

While it is true that the electro negativity of carbon is 2.5 and that of chlorine is 3.0, hence an electro negativity difference of 0.5 exists between carbon and chlorine leading to the presence of four polar covalent bonds in the carbon tetrachloride molecule. We must also observe that the molecule, carbon tetrachloride, has a tetrahedral molecular geometry. This implies that the four dipoles in the molecule are symmetrical and cancel out each other hence the molecule is non polar. Being a non polar molecule, only London forces are expected to be present as an intermolecular force, hence the answer.

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.