91Ó°ÊÓ

Carbon is usually classified as a nonmetal. However, the graphite used in "lead" pencils conducts electricity. Look at a pencil, and list two nonmetallic properties of graphite.

Predict the outcome of the following reactions: (a) \(\mathrm{CuO}(s)+\mathrm{H}_{2}(g)\) (b) \(\mathrm{Na}_{2} \mathrm{O}(s)+\mathrm{H}_{2}(g)\)

Briefly discuss the preparation and properties of carbon monoxide and carbon dioxide.

Magnesium chloride is dissolved in a solution containing sodium bicarbonate. On heating, a white precipitate is formed. Explain what causes the precipitation.

Sodium hydroxide is hygroscopic - that is, it absorbs moisture when exposed to the atmosphere. A student placed a pellet of \(\mathrm{NaOH}\) on a watch glass. A few days later, she noticed that the pellet was covered with a white solid. What is the identity of this solid? (Hint: Air contains \(\mathrm{CO}_{2}\).)

Describe a laboratory and an industrial preparation of nitrogen gas.

Nitrogen can be obtained by (a) passing ammonia over red-hot copper(II) oxide and (b) heating ammonium dichromate [one of the products is \(\mathrm{Cr}(\mathrm{III})\) oxide]. Write a balanced equation for each preparation.

Explain why, under normal conditions, the reaction of zinc with nitric acid does not produce hydrogen.

Explain why two \(\mathrm{N}\) atoms can form a double bond or a triple bond, whereas two \(\mathrm{P}\) atoms normally can form only a single bond.

Hydrogen peroxide can be prepared by treating barium peroxide with sulfuric acid. Write a balanced equation for this reaction.