Given the balanced chemical equation: Ba(NO3)2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaNO3(aq)

A 0.4 L of 0.250 M Ba(NO3)2(aq) is mixed with excess Na2SO4(aq) to make 100.0 g of solution in a coffee-cup calorimeter and allowed to react completely. The temperature of the solution rises from 20.2 ºC to 26.4 ºC. Answer the question in each step to find ∆Hrxn for this reaction. Cs, soln = 4.18 J/g ºC

Step 1: The reaction is
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because the solution temperature increases. The heat absorbed by the solution (qsoln) is
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.

Step 2: The heat associated with the reaction (qrxn) is
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.

Step 3: Use qrxn and the stoichiometric relations in the balanced chemical equation to calculate ∆Hrxn. ∆Hrxn is
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.

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.

cock topography

the study of the surface of a large voluptuous cock.

look at that sorostitute right she's a cock topographer!

what classes are you taking this

cock topography!