A 35.161 mg sample of a chemical known to contain only carbon, hydrogen, sulfur, and oxygen is put into a combustion analysis apparatus, yielding 62.637 mg of carbon dioxide and 25.641 mg of water. In another experiment, 31.321 mg of the compound is reacted with excess oxygen to produce 13.54 mg of sulfur dioxide. Add subscripts to the formula provided to correctly identify the empirical formula of this compound. Do not change the order of the elements.

The empirical formulae is C6H12S02

Explanation:

1. First we need to obtain the mass of each element in the sample and compound formed

Carbon = (62.637 mg * 12.011 g/mol / 44.009 g/mol) = 17.094 mg of Carbon

Hydrogen = ( 25.641 mg * (2 *1..008 g/mol) / 18.015 g/mol) = 2.869 mg of Hydrogen

Sulphur = (13.54 mg * 32.066 g/mol / 64.066 g/mol) = 6.777 mg of Sulphur

2. Next is to determine the percentage composition. Here we divide the respective mass by the mass of the sample

Carbon = 17.094 / 35.161 * 100 = 48.62 %

Hydrogen = 2.869/ 35.161 *100 = 8.16 %

Sulphur = 6.777/ 31.321 *100 = 21.64 %

Oxygen = (100 - (48.62 + 8.16 + 21.64)) = 21.58 %

3. Next is to divide the mass assuming there are 100 mg by the respective atomic masses to obtain the number of moles

Carbon = 48.62 / 12.011 = 4.048 mol

Hydrogen = 8.16 / 1.008 = 8.095 mol

Sulphur = 21.64 / 32.066 = 0.675 mol

Oxygen = 21.58 / 16.000 = 1.348 mol

Next is to divide by the smallest value

Carbon = 4.048/ 0.675 =5.997 = 6

Hydrogen = 8.095 / 0.675 =11.993 =12

Sulphur = 0.675/ 0.675 = 1

Oxygen = 1.348 / 0.675 = 1.997 = 2

So therefore the empirical formulae of the sample is C6H12SO2

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.