Chapter 18: The Representative Elements

Provide a reasonable estimate for the number of atoms in aadult human. Use the information given in Table 18.2.

EDTA is used as a complexing agent in chemical analysis. Solutions of EDTA, usually containing the disodium salt $\mathbf{\text{Na}}{}_{\mathbf{\text{2}}}\mathbf{\text{H}}_{\mathbf{\text{2}}}\mathbf{\text{EDTA}}$, are also used to treat heavy metal poisoning. The equilibrium constant for the following reaction is $\mathbf{6}\mathbf{.7}\mathbf{\times }{\mathbf{10}}^{\mathbf{21}}$:

${\mathbf{\text{Pb}}}^{\mathbf{\text{2+}}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}\mathbf{+}{\mathbf{\text{H}}}_{\mathbf{\text{2}}}{\mathbf{\text{EDTA}}}^{\mathbf{\text{2-}}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}\mathbf{\rightleftharpoons }{\mathbf{\text{PbEDTA}}}^{\mathbf{\text{2-}}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}\mathbf{+}{\mathbf{\text{2H}}}^{\mathbf{\text{+}}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}$

Calculate $\mathbf{\left[}{\mathbf{\text{Pb}}}^{\mathbf{\text{2+}}}\mathbf{\right]}$at equilibrium in a solution originally $\mathbf{\text{0.0050M}}$in ${\mathbf{\text{Pb}}}^{\mathbf{\text{2+}}}$,$\mathbf{\text{0.075M}}$ in ${\mathbf{\text{H}}}_{\mathbf{\text{2}}}{\mathbf{\text{EDTA}}}^{\mathbf{\text{2-}}}$, and buffered at $\mathbf{\text{pH}}\mathbf{=}\mathbf{\text{7.00}}$.

Lead forms compounds in the $\mathbf{+}\mathbf{2}$and $\mathbf{+}\mathbf{4}$oxidation states. All lead (ll) halides are known (and are known to be ionic). Only${\mathbf{\text{PbF}}}_{\mathbf{\text{4}}}$ and${\mathbf{\text{PbCl}}}_{\mathbf{\text{4}}}$ are known among the possible lead (IV) halides. Presumably lead (IV) oxidizes bromide and iodide ions, producing the lead (II) halide and the free halogen:

${\mathbf{\text{PbX}}}_{\mathbf{\text{4}}}\mathbf{\to }{\mathbf{\text{PbX}}}_{\mathbf{\text{2}}}{\mathbf{\text{+X}}}_{\mathbf{\text{2}}}$

Suppose$\mathbf{\text{25.00g}}$ of a lead (IV) halide reacts to form$\mathbf{\text{16.12g}}$ of a lead (II) halide and the free halogen. Identify the halogen.

(a) Many biochemical reactions that occur in cells require relatively high concentrations of potassium ion $\mathbf{\left(}{\mathbf{\text{K}}}^{\mathbf{\text{+}}}\mathbf{\right)}$. The concentration of ${\mathbf{\text{K}}}^{\mathbf{\text{+}}}$in muscle cells is about $\mathbf{\text{0.15M}}$. The concentration of ${\mathbf{\text{K}}}^{\mathbf{\text{+}}}$in blood plasma is about $\mathbf{\text{0.0050M}}$. The high internal concentration in cells is maintained by pumping ${\mathbf{\text{K}}}^{\mathbf{\text{+}}}$from the plasma. How much work must be done to transport role="math" localid="1663854169668" $\mathbf{\text{1.0mole}}$of ${\mathbf{\text{K}}}^{\mathbf{\text{+}}}$from the blood to the inside of a muscle cell at${\mathbf{\text{37}}}^{\mathbf{\text{o}}}\mathbf{\text{C}}$ (normal body temperature)?

(b) When $\mathbf{\text{1.0mole}}$of ${\mathbf{\text{K}}}^{\mathbf{\text{+}}}$is transferred from blood to the cells, do any other ions have to be transported? Why or why not?

(c) Cells use the hydrolysis of adenosine triphosphate, abbreviated $\mathbf{\text{ATP}}$, as a source of energy. Symbolically, this reaction can be represented as

$\mathbf{\text{ATP}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}{\mathbf{\text{+H}}}_{\mathbf{\text{2}}}\mathbf{\text{O}}\mathbf{\left(}\mathbf{I}\mathbf{\right)}\mathbf{\to }\mathbf{\text{ADP}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}{\mathbf{\text{+H}}}_{\mathbf{\text{2}}}{\mathbf{\text{PO}}}_{\mathbf{\text{4}}}^{\mathbf{-}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}$where $\mathbf{\text{ADP}}$represents adenosine diphosphate. For this reaction at ${\mathbf{\text{37}}}^{\mathbf{\text{o}}}\mathbf{\text{C}}$, role="math" localid="1663854582755" $\mathit{K}\mathbf{=}\mathbf{1}\mathbf{.7}\mathbf{\times }{\mathbf{10}}^{\mathbf{5}}$. How many moles of $\mathbf{\text{ATP}}$must be hydrolysed to provide the energy for the transport of $\mathbf{\text{1.0mole}}$of ${\mathbf{\text{K}}}^{\mathbf{\text{+}}}$? Assume standard conditions for the$\mathbf{\text{ATP}}$ hydrolysis reaction.

How long will it take to produce $\mathbf{1}\mathbf{.}\mathbf{00}\mathbf{\times }{\mathbf{10}}^{\mathbf{3}}\mathit{K}\mathit{g}$ of magnesium metal by the electrolysis of molten magnesium chloride using a current of $\mathbf{5}\mathbf{.}\mathbf{00}\mathbf{\times }{\mathbf{10}}^{\mathbf{4}}\mathit{A}$ ?

Supposeof an alkaline earth metal reacts withof water to produceof hydrogen gas at and . Identify the metal and determine of the solution.

What ions are found in hard water? What happens when water is "softened"?

Write balanced equations describing the reaction of sr with each of the following: ${\mathbf{\text{O}}}_{\mathbf{2}}\mathbf{,}{\mathbf{\text{S}}}_{\mathbf{8}}\mathbf{,}{\mathbf{\text{Cl}}}_{\mathbf{2}}\mathbf{,}{\mathbf{\text{P}}}_{\mathbf{4}}\mathbf{,}{\mathbf{\text{H}}}_{\mathbf{2}}\mathbf{,}{\mathbf{\text{H}}}_{\mathbf{2}}\mathbf{\text{O}}$and $\mathit{H}\mathit{C}\mathit{I}$

One harmful effect of acid rain is the deterioration of structures and statues made of marble or limestone, both of which are essentially calcium carbonate. The reaction of calcium carbonate with sulfuric acid yields carbon dioxide, water, and calcium sulfate. Because calcium sulfate is marginally soluble in water, part of the object is washed away by the rain. Write a balanced chemical equation for the reaction of sulfuric acid with calcium carbonate.

What mass of barium is produced when molten BaCl2 is electrolyzed by a current $\mathbf{2}\mathbf{.}\mathbf{50}\mathbf{\times }{\mathbf{10}}^{\mathbf{5}}$A for $\mathbf{6}\mathbf{.}\mathbf{00}\mathbf{}\mathit{h}$?