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13.9 A solution contains 4.00 g NaOH, 5.61 g KOH, and 1.03 g RBOH in 90.0 g of water. The solution has a density of 1.08 g/mL. What is the molality of OH-?
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<p>There are about 0.1 mols NaOH, 0.1 mols 5.61 KOH, and 0.01 mols RbOH. Since these are all strong bases, we assume they completely dissociate, giving us 0.21 mols of OH-. Since molality is (mols solute/kg of solvent) and we know there are 90.0g of water, it's just 0.21/0.090, which gives you 2.33 *m*.</p>