Chapter 20: Problem 90
In large doses, selenium is toxic. However, in moderate intake, selenium is a physiologically important element. How is selenium physiologically important?
Chapter 20: Problem 90
In large doses, selenium is toxic. However, in moderate intake, selenium is a physiologically important element. How is selenium physiologically important?
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Get started for freeHow could you determine experimentally whether the compound $\mathrm{Ga}_{2} \mathrm{Cl}_{4}$ contains two gallium(Il) ions or one gallium(I) and one gallium(III) ion? (Hint: Consider the electron configurations of the three possible ions.)
In many natural waters, nitrogen and phosphorus are the least abundant nutrients available for plant life. Some waters that become polluted from agricultural runoff or municipal sewage become infested with algae. The algae flourish, and fish life dies off as a result. Describe how these events are chemically related.
Captain Kirk has set a trap for the Klingons who are threatening an innocent planet. He has sent small groups of fighter rockets to sites that are invisible to Klingon radar and put a decoy in the open. He calls this the “fishhook” strategy. Mr. Spock has sent a coded message to the chemists on the fighters to tell the ships what to do next. The outline of the message is Fill in the blanks of the message using the following clues. (1) Symbol of the halogen whose hydride has the second highest boiling point in the series of HX compounds that are hydrogen halides. (2) Symbol of the halogen that is the only hydrogen halide, HX, that is a weak acid in aqueous solution. (3) Symbol of the element whose existence on the sun was known before its existence on earth was discovered. (4) The Group 5A element in Table 20.13 that should have the most metallic character. (5) Symbol of the Group 6A element that, like selenium, is a semiconductor. (6) Symbol for the element known in rhombic and monoclinic forms. (7) Symbol for the element that exists as diatomic molecules in a yellow-green gas when not combined with another element. (8) Symbol for the most abundant element in and near the earth’s crust. (9) Symbol for the element that seems to give some protection against cancer when a diet rich in this element is consumed. (10) Symbol for the smallest noble gas that forms compounds with fluorine having the general formula \(\mathrm{AF}_{2}\) and \(\mathrm{AF}_{4}\) (reverse the symbol and split the letters as shown). (11) Symbol for the toxic element that, like phosphorus and antimony, forms tetrameric molecules when uncombined with other elements (split the letters of the symbol as shown). (12) Symbol for the element that occurs as an inert component of air but is a very prominent part of fertilizers and explosives.
List two major industrial uses of hydrogen.
While selenic acid has the formula \(\mathrm{H}_{2} \mathrm{SeO}_{4}\) and thus is directly related to sulfuric acid, telluric acid is best visualized as \(\mathrm{H}_{6} \mathrm{TeO}_{6}\) or \(\mathrm{Te}(\mathrm{OH})_{6}\) a. What is the oxidation state of tellurium in Te(OH) \(_{6} ?\) b. Despite its structural differences with sulfuric and selenic acid, telluric acid is a diprotic acid with \(\mathrm{p} K_{\mathrm{a}_{1}}=7.68\) and \(\mathrm{p} K_{\mathrm{a}_{2}}=11.29 .\) Telluric acid can be prepared by hydrolysis of tellurium hexafluoride according to the equation $$ \mathrm{TeF}_{6}(g)+6 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{Te}(\mathrm{OH})_{6}(a q)+6 \mathrm{HF}(a q) $$ Tellurium hexafluoride can be prepared by the reaction of elemental tellurium with fluorine gas: $$ \mathrm{Te}(s)+3 \mathrm{F}_{2}(g) \longrightarrow \mathrm{TeF}_{6}(g) $$ If a cubic block of tellurium (density \(=6.240 \mathrm{g} / \mathrm{cm}^{3} )\) measuring 0.545 \(\mathrm{cm}\) on edge is allowed to react with 2.34 \(\mathrm{L}\) fluorine gas at 1.06 \(\mathrm{atm}\) and \(25^{\circ} \mathrm{C},\) what is the pH of a solution of \(\mathrm{Te}(\mathrm{OH})_{6}\) formed by dissolving the isolated TeF \(_{6}(g)\) in 115 \(\mathrm{mL}\) solution? Assume 100\(\%\) yield in all reactions.
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