3.83 Calculate the ratio [PbT^-]/[HT^2-] for NTA in equilibrium with PbCO_3 in a

Question

3.83

Calculate the ratio [PbT^-]/[HT^2-] for NTA in equilibrium with PbCO_3 in a medium having [HCO_3^-] = 3.00 Times 10^-3 M (See equation 3.83 for this reactions K value). What does this ratio tell you about the reaction? The increased solubility of carbon dioxide in water with an elevated alkalinity can be illustrated by comparing its solubility in pure water (alkalinity 0) to its solubility in water initially containing 1.00 Times 10^-3 M NaOH (alkalinity 1.00 Times 10^-3 eq/L). The number of moles of CO_2 that will dissolve in a liter of pure water from the atmosphere containing 390 ppm carbon dioxide is Solubility = [CO_2 (aq)] + [HCO_3^-] Substituting values calculated in Section 3.7 gives Solubility = 1.276 Times 10^-5 + 2.38 Times 10^-6 = 1.514 Times 10^-5 M The solubility of CO_2 in water, initially 1.00 Times 10^-3 M in NaOH, is about 100-fold higher because of uptake of CO_2 by the reaction CO_2 (aq)+OH^- rightarrow HCO_3^- so that Solubility = [CO_2 (aq)] + [HCO_3^-] = 1.276 Times 10^-5 + 1.00 Times 10^-3 = 1.01 Times 10^-3 M The kinds and concentrations of metal ions in water are determined largely by the rocks that the water contacts. Metal ions in water, commonly denoted M^n+, exist in numerous forms. A bare metal ion, Ca^2+ for example, cannot exist as a separate entity in water. In order to secure the highest stability of their outer electron shells, metal ions in water are bonded, or coordinated, to other species. These may be water molecules or other stronger bases (electron-donor partners) that might be present. Therefore, metal ions in water solution are present in forms such as the hydrated metal cation M(H_2O)_x^n+. Metal ions in aqueous solution seek to reach a state of maximum stability through chemical reactions including acid-base

Explanation / Answer

the number of moles of CO2 that will dissolved in a litre pure water from the atmosphere containing 390ppm carbon dioxide is

solubility = [CO2(aq)]+[HCO-3]

from the given data substituting values

solubilty = 1.276x10-5+2.38x10-6= 1.514x10-6M

the solubility of CO2 in water, initially 1.00x10-3M in NaOH,

CO2(aq)+OH- --> HCO-3

hence , solubility = [CO2(aq)]+[HCO-3] = 1.276x10-5 + 1.00x10-3 = 1.01x10-3 M

from the given data, NTA in equilibrium with PbCO3 in a medium having

[HCO3-] = 3x10-3M

so that , solubilty =  [CO2(aq)]+[HCO-3] = 1.276 x 10-5 + 3.00x 10-3 = 3.01 x 10-3 M

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