Give the equation: 2k + 2h2o --> 2koh + h2 if 23.5 grams of potassium are reacted with excess water, how many grams of hydrogen will be formed?

0.6058g of Hydrogen wouldbe produced

Explanation:

2K + 2H2O --> 2KOH + H2

Our focus is on potassium and Hydrogen.

The question stated that water in excess, this means that water is not a limiting reactant and what that means is that the amount of product formed is dependent on potassium and not water.

From the equation,

2 mol of potassium produces 1 mol of Hydrogen;

Expressing in terms of mass;

Note that: Mass = Number of moles * Molar mass

78.1966g ( 2 * 39.0983) of potassium produces 2.01588g ( 1 * 2.01588) of hydrogen Hydrogen

How many grams of Hydrogen would then be produced from 23.5g of potassium?

78.1966 = 2.01588

23.5 = x

Upon cross multiplication and solving for x;

x = ( 23.5 * 2.01588) / 78.1966

x = 0.6058g

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.