Chemistry · Chemical equations and stoichiometry
Magnesium hydroxide is the white milky substance in milk of magnesia. What mass
Magnesium hydroxide is the white milky substance in milk of magnesia. What mass of \( M g(O H)_{2} \) is formed when \( 15 m l \) of \( 0.2 M-N a O H \) is combined with \( 12 \mathrm{ml} \) of \( 0.15 M- \) \( M g C l_{2} ? \)
- A. \( 0.087 g \)
- B. \( 0.079 g \)
- C. \( 0.1044 g \)
- D. \( 0.522 g \)
Step-by-step solution
Moles NaOH = 0.015 L × 0.2 mol/L = 0.003 mol; moles MgCl2 = 0.012 L × 0.15 mol/L = 0.0018 mol. Reaction: MgCl2 + 2NaOH → Mg(OH)2 + 2NaCl; requires 2 mol NaOH per 1 mol MgCl2. For 0.0018 mol MgCl2, needed NaOH = 0.0036 mol; only 0.003 mol available, so NaOH limiting. Moles Mg(OH)2 = 0.003/2 = 0.0015 mol. Molar mass Mg(OH)2 = 58.3 g/mol; mass = 0.0015 × 58.3 = 0.08745 g ≈ 0.087 g.
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