Water "softeners" remove metal ions such as Ca2+ and Fe3+ by replacing them with enough Na+ ions to maintain the same number of positive charges in the solution. If 1.0×103 L of "hard" water is 0.015 M Ca2+ and 0.0010 M Fe3+, how many moles of Na+ are needed to replace these ions?

16 moles of Na^+ is needed to replace Ca^2+ and Fe^3+.

Explanation:

Number of moles ions is given by concentration of ions multiplied by volume of hard water.

Concentration of Ca^2+ = 0.015 M

Concentration of Fe^3+ = 0.001 M

Volume of hard = 1×10^3 L

Number of moles of Ca^2+ = 0.015 × 1×10^3 = 15 moles

Number of moles of Fe^3+ = 0.001 × 1×10^3 = 1 mole

Number of moles of Na^+ needed to replace these ions = 15 + 1 = 16 moles.

Explanation:

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