For #2: Odor, Temperature, and color
Answer:
-7.34 kilo Joules is the change in enthaply when 20.0 grams of nitrogen triiodide decomposes.
Explanation:
Mass of nitrogen triiodide = 20.0 g
Moles of nitrogen triiodide = 

According to reaction, 2 moles of nitrogen triiodide gives 290.0 kilo Joules of heat on decomposition ,then 0.05063 moles of nitrogen triiodide will give :

-7.34 kilo Joules is the change in enthaply when 20.0 grams of nitrogen triiodide decomposes.
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Zero error occur in every reading means that the measuring instrument needs to recalibrated and adjusted.
<h3>
What is Zero error?</h3>
This error occurs when a measuring instrument reflects a digit which isn't zero despite the real value being zero.
When this occurs, only the zero screw on the device should be adjusted so as to correct this technical error. This is why recalibration should be the most appropriate solution.
Read more about Zero error here brainly.com/question/4704005
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Answer:
No, i will not use a water pipe consisting of the two metals
Explanation:
Looking at the reduction potential of the both metals, it is clear that an electrochemical cell is set up with iron as the anode and copper as the cathode.
This will make the iron to quickly corrode and eventually destroy the water pipe. It is better to have a set up in which another metal that is higher than iron in the electrochemical series is combined with it.