Select all the correct statements, there is more than one. a. Experiments to determine mechanisms involve looking at indirect evidence to help support or disprove a proposed mechanism.
b. Most intermediates are not typically isolated to determine reaction mechanisms.
c. Transition states can be isolated and characterized to determine reaction mechanisms.
d. Carbocations are very reactive and are typically not isolated for analysis.
e. Carbocations can be routinely isolated (separated from a reaction mixture) and analyzed.
f. Scientists can prove that a specific mechanism exists.
g. Evidence of intermediates sometimes can be seen using techniques such as nuclear magnetic resonance spectroscopy.

Experiments to determine mechanisms involve looking at indirect evidence to help support or disprove a proposed mechanism.

Most intermediates are not typically isolated to determine reaction mechanisms.

Carbocations are very reactive and are typically not isolated for analysis.

Scientists can prove that a specific mechanism exists.

Evidence of intermediates sometimes can be seen using techniques such as nuclear magnetic resonance spectroscopy

Explanation:

The study of reaction mechanism and chemical kinetics often form the main thrust of study in organic, inorganic and physical chemistry.

We often want to know the actual processes involved in the conversion of one specie to another. Unfortunately, this information may have to be obtained indirectly by certain chemical reactions or by the use of new instrumental methods such as nuclear magnetic resonance spectroscopy.

Many organic reactions have carbocation intermediates. These carbocations are relatively short-lived and are transient intermediates which are rarely isolated unless they are isolated in a molecular cage using a macromolecule or in superacids.

By intensive study, scientists can proof or disprove the authenticity of any proposed mechanism.

We must know that a transition state has partial bonds. It is often an extremely short-lived specie which cannot be isolated.

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.