A piece of copper metal is dipped into an aqueous solution of AgNO3. Which net ionic equation describes the reaction that occurs? A. Cu(s) + 2Ag+(aq) + 2NO3–(aq) → 2AgNO3(s) + Cu2+(aq) B. 2Ag+(aq) + 2NO3–(aq) → 2AgNO3(s) C. Cu(s) + 2Ag+(aq) → 2Ag(s) + Cu2+(aq) D. 2NO3–(aq) + Cu2+(aq) → Cu(s) + 2Ag(s)

Cu(s) + 2Ag+(aq) → 2Ag(s) + Cu2+(aq) (option C)

Explanation:

Step 1: the unbalanced equation

Cu(s) + AgNO3(ag) → Ag + Cu(NO3)2

Step 2: The balanced equation

Cu(s) + AgNO3(ag) → Ag + Cu(NO3)2

On the left side we have 1x NO3 (in AgNO3), on the right side we have 2x NO3, in Cu(NO3)2. To balance the amount of NO3 on both sides we have to multiply AgNO3, on the left side, by 2

Cu(s) + 2AgNO3(ag) → Ag + Cu(NO3)2

On the left side we have 2x Ag (in 2AgNO3) , on the right side we have 1x Ag. To balance the amount of Ag on both sides we have to multiply Ag, on the right side, by 2. Now the equation is balanced.

Cu(s) + 2AgNO3(ag) → Ag(s) + Cu(NO3)2(aq)

The net ionic equation, for which spectator ions are omitted - remember that spectator ions are those ions located on both sides of the equation - will , after canceling those spectator ions in both side (Ba^2+ and Br-), look like this:

Cu(s) + 2Ag+(aq) → 2Ag(s) + Cu2+(aq) (option C)

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.

bcde is the incorrect answer it is a