Water-soluble toxic chromium compounds are waste products of electroplating operations, but the chromium can be precipitated as Cr(OH)₃ to remediate the water.How many grams of solid NaOH (40.00 g/mol) are needed to remove the chromium from 200.L of a solution that is 1.0 *10^-3 M in Cr³⁺?

Question

Quizplus · Accepted Answer

The correct answer is A because 24 g of solid NaOH are needed to remove the chromium from 200.L of a solution that is 1.0 F1F1F1S1F1F1F10 10^{F1F1F1S1F1F1F103} M in Cr^{3F1F1F1S1F1F1F10}. The balanced chemical equation for the reaction is:Cr^{3F1F1F1S1F1F1F10} + 3NaOH → Cr(OH)₃ + 3Na^{F1F1F1S1F1F1F10}From the balanced chemical equation, we can see that 1 mole of Cr^{3F1F1F1S1F1F1F10} reacts with 3 moles of NaOH. Therefore, the number of moles of NaOH needed to remove the chromium from 200.L of a solution that is 1.0 F1F1F1S1F1F1F10 10^{F1F1F1S1F1F1F103} M in Cr^{3F1F1F1S1F1F1F10} is:200.L × 1.0 F1F1F1S1F1F1F10 10^{F1F1F1S1F1F1F103} M × 3 moles NaOH/1 mole Cr^{3F1F1F1S1F1F1F10} = 600 moles NaOHThe mass of NaOH needed is:600 moles NaOH × 40.00 g/mol = 24,000 g = 24 gTherefore, the correct answer is A.

Water-Soluble Toxic Chromium Compounds Are Waste Products of Electroplating Operations