What is the number of moles of H2 produced when 23 g of sodium react with water according to the equation 2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)

0.5 mole of H₂.

Explanation:

We'll begin by calculating the number of mole in 23 g of Na. This can be obtained as follow:

Mass of Na = 23 g

Molar mass of Na = 23 g/mol

Mole of Na =?

Mole = mass / Molar mass

Mole of Na = 23 / 23

Mole of Na = 1 mole

Next, the balanced equation for the reaction.

2Na + 2H₂O —> 2NaOH + H₂

From the balanced equation above,

2 moles of Na reacted to produce 1 mole H₂.

Finally, we shall determine the number of mole of H₂ produced by the reaction of 23 g (i.e 1 mole) of Na. This can be obtained as follow:

From the balanced equation above,

2 moles of Na reacted to produce 1 mole H₂.

Therefore, 1 mole of Na will react to produce = (1 × 1) / 2 = 0.5 mole of H₂.

Thus, 0.5 mole of H₂ is obtained from the reaction.

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 answers would be

the first one and the second one