Chemistry, 16.07.2020 09:01 lin550

An open flask sitting in a lab refrigerator looks empty, but it is actually filled with a mixture of gases called air. If the flask volume is 4.00 L, and the air is at standard temperature and pressure, how many gaseous molecules does the flask contain

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Answer from: qwertylol12345

$1.07\times 10^{23}$ molecules

Explanation:

According to the ideal gas equation:

PV=nRT

P = Pressure of the gas = 1 atm ( at STP)

V= Volume of the gas = 4.00 L

T= Temperature of the gas in kelvin = 273 K ( at STP)

R= Gas constant = 0.0821Latm/kmol

n= moles of gas= ?

Putting in the values we get:

$1atm\times 4.00L=n\times 0.0821Latm/Kmol\times 273K$

n=0.178mol

Now 1 mole of any substance contains $6.023\times 10^{23}$ molecules at STP

Thus 0.178 mole of any substance contains = $\frac{6.023\times 10^{23}}{1}\times 0.178=1.07\times 10^{23}$ molecules at STP

Thus there are $1.07\times 10^{23}$ gaseous molecules in the flask.

Answer from: Quest

668900 atoms in total

Answer from: Quest

Answer: abeexplanation:

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.

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