Look at the four chemical reactions. Reaction 1: 4Na + O2 → 2Na2O
Reaction 2: 2NaCl → 2Na + Cl2
Reaction 3: CaCO3 → CaO + CO2
Reaction 4: 2KClO33 → 2KCl + 3O2

Which statement identifies the reaction that is different from the rest and explains correctly why it is different?

Reaction 2, because two ions are interchanged
Reaction 2, because two products are formed
Reaction 1, because a single product is formed
Reaction 1, because a single ion is replaced in a compound

3 hours because it is a decent distance.

answer: you could do some invislibe ink.

explanation: i will tell you how to if u answer my question.

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.

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.