What change occurs during the reaction: mno4- > mn2+? five electrons are lost. three electrons are lost. five electrons are gained. three electrons are gained.

Five electrons are gained.

Explanation:

Oxidation number or oxidation state of an atom in a chemical compound is  the number of electrons lost or gained. It is also defined as the degree of oxidation of the atom in the compound.

This is a theoretical number which can help to decipher the oxidation and reduction in a redox reaction.

Oxidation is the loss of electrons. The specie which is oxidized has has elevation in its oxidation state as compared in the reactant and the products.

The given reaction is shown below as:

Manganese in has oxidation state of +7

Manganese in has an oxidation state of +2

It reduces from +7 to +2 . It means that 5 electrons are gained.

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.