Calculate mass (grams) needed for the following base equivalent: 0.18 mEq of Mg(OH)₂.

• A. 5.3×10^–3 g
• B. 0.010 g
• C. 10 g
• D. 5.3 g

Answer: (A)

Verified step by step guidance

1. Understand that the problem is asking for the mass of Mg(OH)_2 needed to provide 0.18 milliequivalents (mEq) of base.
2. Recall that the equivalent weight of a compound is the molecular weight divided by the number of equivalents per mole. For Mg(OH)_2, which provides 2 hydroxide ions (OH^-), the number of equivalents is 2.
3. Calculate the molar mass of Mg(OH)_2 by adding the atomic masses: Mg (24.31 g/mol), O (16.00 g/mol), and H (1.01 g/mol). The formula is Mg(OH)_2, so the molar mass is 24.31 + 2(16.00 + 1.01).
4. Determine the equivalent weight of Mg(OH)_2 by dividing its molar mass by the number of equivalents (2).
5. Use the formula: mass (g) = (mEq × equivalent weight) / 1000 to find the mass in grams needed for 0.18 mEq of Mg(OH)_2.