QuestionJune 22, 2025

A chemist dissolves 138 mg of pure hydroiodic acid in enough water to make up 210.mL of solution. Calculate the pH of the solution. Be sure your answer has the correct number of significant digits. square

A chemist dissolves 138 mg of pure hydroiodic acid in enough water to make up 210.mL of solution. Calculate the pH of the solution. Be sure your answer has the correct number of significant digits. square
A chemist dissolves 138 mg of pure hydroiodic acid in enough water to make up 210.mL of solution. Calculate the pH of the solution. Be sure your answer has
the correct number of significant digits.
square

Solution
4.6(235 votes)

Answer

0.35 Explanation 1. Calculate moles of hydroiodic acid Convert mass to grams: 138 \text{ mg} = 0.138 \text{ g}. Use molar mass of HI (127.91 \text{ g/mol}) to find moles: \text{moles} = \frac{0.138}{127.91}. 2. Calculate concentration of HI Volume in liters: 210 \text{ mL} = 0.210 \text{ L}. Concentration: \text HI = \frac{\text{moles}}{0.210}. 3. Determine pH from concentration HI is a strong acid, dissociates completely: \text H}^+\text{ = \text HI . **pH = -\log(\text H}^+\text{ )**.

Explanation

1. Calculate moles of hydroiodic acid<br /> Convert mass to grams: $138 \text{ mg} = 0.138 \text{ g}$. Use molar mass of HI ($127.91 \text{ g/mol}$) to find moles: $\text{moles} = \frac{0.138}{127.91}$.<br /><br />2. Calculate concentration of HI<br /> Volume in liters: $210 \text{ mL} = 0.210 \text{ L}$. Concentration: $\text{[HI]} = \frac{\text{moles}}{0.210}$.<br /><br />3. Determine pH from concentration<br /> HI is a strong acid, dissociates completely: $\text{[H}^+\text{]} = \text{[HI]}$. **pH = -\log(\text{[H}^+\text{]})**.
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