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 freeSulfur forms a wide variety of compounds in which it has \(+6\) \(+4,+2,0,\) and \(-2\) oxidation states. Give examples of sulfur compounds having each of these oxidation states.
Sodium tripolyphosphate \(\left(\mathrm{Na}_{5} \mathrm{P}_{3} \mathrm{O}_{10}\right)\) is used in many synthetic detergents. Its major effect is to soften the water by complexing \(\mathrm{Mg}^{2+}\) and \(\mathrm{Ca}^{2+}\) ions. It also increases the efficiency of surfactants, or wetting agents, that lower a liquid's surface tension. The pK value for the formation of \(\mathrm{MgP}_{3} \mathrm{O}_{10}^{3-}\) is \(-8.60 .\) The reaction is $$ \mathrm{Mg}^{2+}(a q)+\mathrm{P}_{3} \mathrm{O}_{10}^{5-}(a q) \rightleftharpoons \mathrm{MgP}_{3} \mathrm{O}_{10}^{3-}(a q) $$ Calculate the concentration of \(\mathrm{Mg}^{2+}\) in a solution that was originally \(50 . \mathrm{ppm} \mathrm{Mg}^{2+}(50 . \mathrm{mg} / \mathrm{L} \text { of solution) after } 40 . \mathrm{g} \text { of }\) \(\mathrm{Na}_{5} \mathrm{P}_{3} \mathrm{O}_{10}\) is added to 1.0 \(\mathrm{L}\) of the solution.
In each of the following pairs of substances, one is stable and known, and the other is unstable. For each pair, choose the stable substance, and explain why the other is unstable. a. \(\mathrm{NF}_{5}\) or \(\mathrm{PF}_{5} \quad\) b. AsF_r \(\mathrm{AsI}_{5} \quad\) c. \(\mathrm{NF}_{3}\) or \(\mathrm{NBr}_{3}\)
Hydrogen is produced commercially by the reaction of methane with steam: $$ \mathrm{CH}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow \mathrm{CO}(g)+3 \mathrm{H}_{2}(g) $$ a. Calculate \(\Delta H^{\circ}\) and \(\Delta S^{\circ}\) for this reaction (use the data in Appendix 4\()\) b. What temperatures will favor product formation at standard conditions? Assume \(\Delta H^{\circ}\) and \(\Delta S^{\circ}\) do not depend on temperature.
Write equations describing the reactions of Sn with each of the following: \(\mathrm{Cl}_{2}, \mathrm{O}_{2},\) and \(\mathrm{HCl}\) .
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