Multiple Choice
Which of the following salts would produce a basic solution?
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17. Acid and Base Equilibrium
The pH Scale
Multiple Choice
A 345 mL bottle of antacid (Mg(OH)2) contains 1.45 × 10−2 moles of hydroxide ions. Determine pH and pOH of the antacid.
A
pH = 12.384
pOH = 1.616
pOH = 1.616
B
pH = 12.623
pOH = 1.377
pOH = 1.377
C
pH = 12.161
pOH = 1.839
pOH = 1.839
D
pH = 12.338
pOH = 1.662
pOH = 1.662
Verified step by step guidance1
First, understand that the antacid contains magnesium hydroxide, Mg(OH)2, which dissociates in water to produce hydroxide ions (OH⁻). The dissociation can be represented as: Mg(OH)2 → Mg²⁺ + 2OH⁻.
Given that there are 1.45 × 10⁻² moles of hydroxide ions in the solution, calculate the concentration of OH⁻ ions. Since the volume of the solution is 345 mL, convert this to liters by dividing by 1000, resulting in 0.345 L.
Calculate the concentration of OH⁻ ions using the formula: [OH⁻] = moles of OH⁻ / volume in liters. Substitute the given values to find [OH⁻].
Use the concentration of OH⁻ ions to find the pOH of the solution. The formula for pOH is: pOH = -log[OH⁻]. Substitute the concentration of OH⁻ into this formula to calculate pOH.
Finally, calculate the pH of the solution using the relationship between pH and pOH: pH + pOH = 14. Rearrange this equation to solve for pH: pH = 14 - pOH. Substitute the calculated pOH to find the pH.
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