91Ó°ÊÓ

What is coal?

Describe two chemical differences between \(\mathrm{CO}\) and \(\mathrm{CO}_{2}\).

Describe the reaction between \(\mathrm{CO}_{2}\) and \(\mathrm{OH}^{-}\) in terms of a Lewis acid-base reaction.

Draw a Lewis structure for the \(\mathrm{C}_{2}^{2-}\) ion.

Unlike \(\mathrm{CaCO}_{3}, \mathrm{Na}_{2} \mathrm{CO}_{3}\) does not readily yield \(\mathrm{CO}_{2}\) when heated. On the other hand, \(\mathrm{NaHCO}_{3}\) undergoes thermal decomposition to produce \(\mathrm{CO}_{2}\) and \(\mathrm{Na}_{2} \mathrm{CO}_{3}\). (a) Write a balanced equation for the reaction. (b) How would you test for the \(\mathrm{CO}_{2}\) evolved? [Hint: Treat the gas with limewater, an aqueous solution of \(\left.\mathrm{Ca}(\mathrm{OH})_{2} .\right]\)

Two solutions are labeled A and B. Solution A contains \(\mathrm{Na}_{2} \mathrm{CO}_{3},\) and solution \(\mathrm{B}\) contains \(\mathrm{NaHCO}_{3} .\) Describe how you would distinguish between the two solutions if you were provided with an \(\mathrm{MgCl}_{2}\) solution. (Hint: You need to know the solubilities of \(\mathrm{MgCO}_{3}\) and \(\mathrm{MgHCO}_{3} .\) )

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

A few drops of concentrated ammonia solution added to a calcium bicarbonate solution cause a white precipitate to form. Write a balanced equation for the reaction.

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 \(\mathrm{CO}_{2}\).)

A piece of red-hot magnesium ribbon will continue to burn in an atmosphere of \(\mathrm{CO}_{2}\) even though \(\mathrm{CO}_{2}\) does not support combustion. Explain.