Asample of gas contains 0.1300 mol of n2(g) and 0.2600 mol of o2(g) and occupies a volume of 23.9 l. the following reaction takes place: n2(g) + 2o2(g)2no2(g) calculate the volume of the sample after the reaction takes place, assuming that the temperature and the pressure remain constant.

Answer : The volume of the sample after the reaction takes place is, 15.93 liters.

Explanation : Given,

Moles of = 0.13 mole

Moles of = 0.26 mole

Initial volume of gas = 23.9 L

First we have to calculate the moles of gas.

The balanced chemical reaction is :

From the balanced reaction, we conclude that

As, 1 mole of react with 2 moles of to give 2 moles of .

So, 0.13 mole of react with moles of to give moles of .

According to the Avogadro's Law, the volume of the gas is directly proportional to the number of moles of the gas at constant pressure and temperature.

or,

where,

= initial volume of gas = 23.9 L

= final volume of gas = ?

= initial moles of gas = 0.13 + 0.26 = 0.39 mole

= final moles of gas = 0.26 mole

Now put all the given values in the above formula, we get the final temperature of the gas.

Therefore, the volume of the sample after the reaction takes place is, 15.93 liters.

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.

that tool would be a compass