Rust (fe2o3) forms on abandoned cars such as the one in this photo through a series of reactions between iron in the car and oxygen in the atmosphere. the unbalanced chemical equation is given below. fe(s)+o2→fe2o3which element is oxidized and which is reduced during the formation of rust? a. is oxidized b. is reduced

Fe has been oxidized

O₂ has been reduced

Explanation:

Here we are going to determine the change in oxidation states and answer the question, remembering that oxidation is the loss of electrons and reduction is the gaining of electrons from the equation:

                                       4Fe     +         3O2→         2Fe2O3

oxidation states                 0                    0               3⁺     2⁻

so we see that oxygen goes from 0 to 2⁻ so it has been reduced, iron goes from 0 to 3⁺ so it has been oxidized.

We could also  answer this question  by noticing that iron has been combined with oxigen therefore it has been oxidized and oxigen has been reduced. I solved the question by determining the change in oxidation states because is more general and applie to any oxidation-reduction reaction

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.