Chapter 24

What is the main characteristic that determines whether or not an element is a main-group element?

Does the metallic characteristic of a main-group element increase or decrease as we move down a family? Explain why.

Briefly define each term. a. orthosilicate b. amphibole c. pyroxene d. pyrosilicate e. feldspar

Why does boron form electron-deficient bonds? Provide an example.

Explain why solid \(\mathrm{CO}_{2}\). is referred to as dry ice.

Describe how nitrogen can be separated from the other components of air.

In the pyroxene kanoite, the formula unit has two \(\mathrm{SiO}_{3}^{2-}\) units and is balanced by manganese and magnesium ions. Determine the formula unit of kanoite. Assume that the oxidation state of Mn is +2 .

Tremolite is a double-chain silicate in the amphibole class. Use charge balancing to determine how many hydroxide ions are in the formula for tremolite, \(\mathrm{Ca}_{2} \mathrm{Mg}_{5} \mathrm{Si}_{8} \mathrm{O}_{22}(\mathrm{OH})_{x}\)

How are the silica tetrahedrons linked for CaSiO \({ }_{3}\) ? Which class of silicates does this compound belong to?

An uncommon mineral of boron is ulexite, \(\mathrm{NaCaB}_{5} \mathrm{O}_{9} \cdot 8 \mathrm{H}_{2} \mathrm{O}\). How many grams of boron can be produced from \(5.00 \times 10^{2} \mathrm{~kg}\) of ulexite-bearing ore if the ore contains \(0.032 \%\) ulexite by mass and the process has an \(88 \%\) yield?

Explain why the bond angles in \(\mathrm{BCl}_{3}\) and \(\mathrm{NCl}_{3}\) are different.

Predict the number of vertices and faces on each closo-borane. a. \(\mathrm{B}_{6} \mathrm{H}_{6}^{2-}\) b. \(\mathrm{B}_{12} \mathrm{H}_{12}^{2-}\)

Predict the number of vertices and faces on each closo-borane. a. \(\mathrm{B}_{4} \mathrm{H}_{4}^{2-}\) b. \(\mathrm{B}_{9} \mathrm{H}_{9}^{2-}\)

Describe the differences among a closo-borane, a nido-borane, and an arachno- borane.

Describe the difference between regular charcoal and activated charcoal.

Explain why the structure of charcoal allows carbon to act as a good filter while the diamond structure does not.

Describe the difference between an ionic carbide and a covalent carbide. Which types of atoms will form these carbides with carbon?

Give the oxidation state for carbon in: a. CO b. \(\mathrm{CO}_{2}\) c. \(\mathrm{C}_{3} \mathrm{O}_{2}\)

Write a balanced reaction for the gas release reaction of AlkaSeltzer, sodium bicarbonate with citric acid, \(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}\). (The acid is a triprotic acid and consists of a chain of three carbon atoms, each with a carboxylic acid group, COOH.)

Describe the differences in the allotropes of white and red phosphorus. Explain why red phosphorus is more stable.

Rank the nitrogen ions from the one with \(\mathrm{N}\) in the highest oxidation state to the one with \(\mathrm{N}\) in the lowest. \(\mathrm{N}_{3}^{-}, \mathrm{N}_{2} \mathrm{H}_{5}^{+}, \mathrm{NO}_{3}^{-}, \mathrm{NH}_{4}^{+}, \mathrm{NO}_{2}^{-}\)

Determine the oxidation state of \(\mathrm{N}\) in the compounds in the reaction for the formation of nitric acid. Identify the oxidizing agent and the reducing agent. $$ 3 \mathrm{NO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 2 \mathrm{HNO}_{3}(l)+\mathrm{NO}(g) $$

Draw the Lewis structures for the phosphorus halides \(\mathrm{PCl}_{3}\) and \(\mathrm{PCl}_{5}\). Describe their VSEPR shape.

Explain why either greatly decreasing or increasing the percentage of oxygen in the atmosphere is dangerous.

Identify each compound as an oxide, peroxide, or superoxide. a. \(\mathrm{LiO}_{2}\) b. \(\mathrm{CaO}\) c. \(\mathrm{K}_{2} \mathrm{O}_{2}\)

Identify each compound as an oxide, peroxide, or superoxide. a. MgO b. \(\mathrm{Na}_{2} \mathrm{O}_{2}\) c. \(\mathrm{CsO}_{2}\)

Determine the oxidation state of Xe and give the VSEPR structure for each compound. a. \(\mathrm{XeF}_{2}\) b. \(\mathrm{XeF}_{6}\) c. XeOF \(_{4}\)

Describe the shape of each halogen compound. a. \(\mathrm{BrF}_{4}^{-}\) b. IF \(_{3}\) 3 c. \(\mathrm{BrO}_{2}{\underline{\phantom{xx}}}^{-}\) d. \(\mathrm{ClO}_{4}^{-}\)

Describe the difference in the types of bonds (single, double, triple) and the shapes of the following two iodine ions: \(\mathrm{ICl}_{4}^{-}\) and \(\mathrm{IO}_{4}\).

The halogens form oxoacids with different amounts of oxygen. Explain why \(\mathrm{HClO}_{4}\) is a stronger acid than \(\mathrm{HClO}_{2}\).

Determine the ratio of effusion rates of HCl compared to each gas. a. \(\mathrm{Cl}_{2}\) b. HF c. HI

Calculate the ratio of effusion rates for each pair of gases. a. \({ }^{238} \mathrm{UF}_{6}\) and \(\mathrm{ClF}\) b. \({ }^{238} \mathrm{UF}_{6}\) and \({ }^{235} \mathrm{UF}_{6}\)

Sodium peroxide is a very powerful oxidizing agent. Balance the reaction of sodium peroxide with elemental iron to give sodium oxide and \(\mathrm{Fe}_{3} \mathrm{O}_{4}\).

Sulfur dioxide is a reducing agent. When it is bubbled through an aqueous solution containing \(\mathrm{Br}_{2}\), a red-colored solution, it reduces the bromine to colorless bromide ions and forms sulfuric acid. Write a balanced equation for this reaction and identify the oxidizing and reducing agent.

Explain why fine particles of activated charcoal can absorb more (as a filter) than large briquettes of charcoal.

The two major components of the atmosphere are the diatomic molecules of nitrogen and oxygen. Explain why pure nitrogen is used as a protective atmosphere in the laboratory and pure oxygen is much more reactive.

Explain why nitrogen can form compounds with many different oxidation numbers.

Describe how sodium dihydrogen phosphate can be used as a pH buffering agent.

Explain why fluorine is found only with the oxidation state of-1 or \(0,\) while the other halogens are found in compounds with other oxidation states.

Why do some substances burn in fluorine gas even if they do not burn in oxygen gas?

Explain why \(\mathrm{SO}_{2}\) is used as a reducing agent but \(\mathrm{SO}_{3}\) is not.

Have each group member select a different element from this list: \(\mathrm{B}, \mathrm{C}, \mathrm{N}, \mathrm{O},\) and \(\mathrm{F} .\) Have all group members look up the following values for their elements: valence electron configuration, covalent atomic radius, effective nuclear charge, first ionization energy, and Pauling electronegativity. All members should compare the values for their elements with those of the group. Repeat with \(\mathrm{O}, \mathrm{S}, \mathrm{Se},\) Te, and Po. Account for the trends you see by referring to quantum-mechanical shells. Note and provide a tentative explanation for any exceptions to trends you observe.

As a group, create a single schematic drawing of a factory that uses the Haber-Bosch process and the Ostwald process to make \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) fertilizer. The factory may only take in \(\mathrm{N}_{2}(g), \mathrm{H}_{2}(g)\) and \(\mathrm{O}_{2}(g) .\) Pass your diagram around the group and have each group member add one step in the process. Where might the factory obtain \(\mathrm{H}_{2} ?\)