A $0.800 g$ antacid tablet containing $Mg (OH) X_{2}$ (molar mass $58$ ) is dissolved in $50.0 mL$ of $0.200 M$ $HCl$ . The excess acid needs $20.0 mL$ of $0.150 M$ $NaOH$ . Assuming no other base is present, the mass percent of $Mg (OH) X_{2}$ is

A50.8%
B36.3%
C25.4%
D12.7%

Answer: C

HCl taken = 0.0100 mol; excess = 0.0200 x 0.150 = 0.0030 mol; consumed = 0.0070 mol. Mg(OH)2 neutralises 2 H+, so mol = 0.0035, mass = 0.2030 g. Percent = 0.2030/0.800 x 100 = 25.38%.

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A 0.800 g antacid tablet containing Mg(OH)X2​ (molar mass 58) is dissolved in 50.0 mL of 0.200 M HCl. The excess acid needs 20.0 mL of 0.150 M NaOH. Assuming no other base is present, the mass percent of Mg(OH)X2​ is

Answer: C

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A $0.800 g$ antacid tablet containing $Mg (OH) X_{2}$ (molar mass $58$ ) is dissolved in $50.0 mL$ of $0.200 M$ $HCl$ . The excess acid needs $20.0 mL$ of $0.150 M$ $NaOH$ . Assuming no other base is present, the mass percent of $Mg (OH) X_{2}$ is