Silver nitrate reacts with calcium chloride as shown.
2 AgNO3 + CaCl2 → 2 AgCl + Ca(NO3)2
How many grams of CaCl2 would be required to completely react with 420 mL of
0.506 M AgNO3 solution?
Answer in units of grams.

11.8g of CaCl₂ would be required

Explanation:

To solve this question we need to find the moles of AgNO₃ in the solution. Thus, and using the chemical reaction we can find the moles of CaCl₂ required for a complete reaction and its mass as follows:

Moles AgNO₃:

420mL = 0.420L * (0.506mol / L) = 0.213 moles AgNO₃

Moles CaCl₂:

Based on the chemical reaction, 2 moles of AgNO₃ react per mole of CaCl₂.

The moles of CaCl₂ that will react are:

0.213 moles AgNO₃ * (1mol CaCl₂ / 2 mol AgNO₃) = 0.106 moles CaCl₂

Mass CaCl₂ -Molar mass: 110.98g/mol-

0.106 moles CaCl₂ * (110.98g / mol) =

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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.