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Multiple Choice
How many grams of Mg(OH)2 are required to completely neutralize 20 mL of 0.1 M HCl?
A
0.145 g
B
0.116 g
C
0.029 g
D
0.058 g
Verified step by step guidance
1
Write the balanced chemical equation for the reaction: \( \text{Mg(OH)}_2 + 2\text{HCl} \rightarrow \text{MgCl}_2 + 2\text{H}_2\text{O} \). This shows that one mole of Mg(OH)2 reacts with two moles of HCl.
Calculate the moles of HCl present in the solution using the formula: \( \text{moles} = \text{concentration} \times \text{volume} \). Here, the concentration is 0.1 M and the volume is 20 mL (which needs to be converted to liters by dividing by 1000).
Use the stoichiometry from the balanced equation to find the moles of Mg(OH)2 needed. Since 1 mole of Mg(OH)2 neutralizes 2 moles of HCl, divide the moles of HCl by 2 to find the moles of Mg(OH)2 required.
Calculate the mass of Mg(OH)2 needed using the formula: \( \text{mass} = \text{moles} \times \text{molar mass} \). The molar mass of Mg(OH)2 is calculated by adding the atomic masses of Mg, O, and H: \( 24.31 + 2(16.00) + 2(1.01) \).
Convert the calculated mass of Mg(OH)2 to grams to find the final answer.