According to the following reaction, how much energy is required to decompose 55.0 kg of fe3o4? the molar mass of fe3o4 is 231.55 g mol-1. fe3o4(s) → 3fe(s) + 2o2(g) δrh° = +1118 kj

The first step is to convert the 55 kg of Fe₃O₄ to moles by using the molar mass, that is, 231.55 g/mol (55 kg = 55000 gms),

55000 gms × 1 mole / 231.55 gms = 237.53 moles of Fe₃O₄

For the decomposition of every 1 mole of Fe₃O₄, +1118 kJ of energy is needed. Therefore, the energy needed to decompose 237.53 moles will be:

237.53 moles of Fe₃O₄ × 1118 kJ / 1 mole = 265558 kJ

Thus, there is a need of 265558 kJ of energy to decompose 55 kg of Fe₃O₄.

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.

the atomic number will stay the same no matter how many electrons it has, so it doesn’t decrease nor increase. it’ll only change with a different number of protons