2. When washing clothes, the presence of manganese may lead to staining. Specifically, water with a manganese [Mn2* (ag)] concentration larger than 0.1 mg/L (1.8 x 10-6 M) may cause clothes to be...

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Extracted text: 2. When washing clothes, the presence of manganese may lead to staining. Specifically, water with a manganese [Mn2* (ag)] concentration larger than 0.1 mg/L (1.8 x 10-6 M) may cause clothes to be stained by the manganese upon oxidation. This can be remedied by reducing the amount of Mn2+ in the water through addition of a base, which precipitate manganese ions in the form of Mn(OH)2 (Ksp = 2 x 10-13). What pH is needed to keep the concentration of Mn2+ in water equal to 1.8 x 10-6 M?