1. Consider a so-called 'open system', i.e., a volume of 1L demineralized water is out into...

Transcribed Image Text:

1. Consider a so-called 'open system', i.e., a volume of 1L demineralized water is out into the open air at 25°C. Na,C204 (sodium oxalate, 134g mol-1) can be dissolved in the given volume before precipitation occurs; this happens at 34.1 g L-1. (a) What is the solubility product, Ksp, of the sodium oxalate? (1pt) (b) If no oxalate is added, the equilibrium pH is 5.66. What is the corresponding speciation of the carbonate species? (0.5pt) How is the equilibrium pH determined? (0.5pt) (c) If 0.2g of the sodium oxalate is added, the equilibrium pH is 6.35. What is the corresponding speciation of the carbonate and the oxalate species? (1pt) [H,L] [H*][HL*] Oxalate (L = C20,) logK = 1.23 [HL] [H*][L*] logK = 4.19 [H,L] [H*][HL*] Carbonate (L = co,?) logK = 6.36 [HL] [H*][L*] logk = 10.33 Note: Carbon dioxide, at pressure of 10-3.5 atm in the atmosphere has the characteristics: со, (0) + H,о о н,со, (ад) log(H,CO3) = -1.46 + logPco, (atm) Surface water is sampled with a Winkler bottle of 297.6mL. In the analysis 4mL of MnSO4 solution and 4mL of KOH/KI are added. After adding the acid, using 2.5mL of H2S04, the solution is brought into an Erlenmeyer. The subsequent titration requires 10.4ml of a 0.035M Na,S203 solution. What is the value for DO? 1. Consider a so-called 'open system', i.e., a volume of 1L demineralized water is out into the open air at 25°C. Na,C204 (sodium oxalate, 134g mol-1) can be dissolved in the given volume before precipitation occurs; this happens at 34.1 g L-1. (a) What is the solubility product, Ksp, of the sodium oxalate? (1pt) (b) If no oxalate is added, the equilibrium pH is 5.66. What is the corresponding speciation of the carbonate species? (0.5pt) How is the equilibrium pH determined? (0.5pt) (c) If 0.2g of the sodium oxalate is added, the equilibrium pH is 6.35. What is the corresponding speciation of the carbonate and the oxalate species? (1pt) [H,L] [H*][HL*] Oxalate (L = C20,) logK = 1.23 [HL] [H*][L*] logK = 4.19 [H,L] [H*][HL*] Carbonate (L = co,?) logK = 6.36 [HL] [H*][L*] logk = 10.33 Note: Carbon dioxide, at pressure of 10-3.5 atm in the atmosphere has the characteristics: со, (0) + H,о о н,со, (ад) log(H,CO3) = -1.46 + logPco, (atm) Surface water is sampled with a Winkler bottle of 297.6mL. In the analysis 4mL of MnSO4 solution and 4mL of KOH/KI are added. After adding the acid, using 2.5mL of H2S04, the solution is brought into an Erlenmeyer. The subsequent titration requires 10.4ml of a 0.035M Na,S203 solution. What is the value for DO?

Answer rating: 100% (QA)

1 a Ksp 00659 or 65910 2 b At pH566 log K636 s... View the full answer