Solve the Problem $\mathrm { pH }$ Scale to Represent the Level of Acidity or Alkalinity of Scale

question 234

Multiple Choice

Solve the problem.
-Scientists use the $\mathrm { pH }$ scale to represent the level of acidity or alkalinity of a liquid. This is based on the molar concentration of hydronium ions, $\left[ \mathrm { H } ^ { + } \right]$ . Since the values of $\left[ \mathrm { H } ^ { + } \right]$ vary over a large range, $1 \times 10 ^ { 0 }$ mole per liter to $1 \times 10 ^ { - 14 }$ mole per liter $( \mathrm { mol } / \mathrm { L } )$ , a logarithmic scale is used to compute the $\mathrm { pH }$ . The formula $\mathrm { pH } = - \log \left[ \mathrm { H } ^ { + } \right]$ represents the $\mathrm { pH }$ of a liquid as a function of its concentration of hydronium ions, $\left[ \mathrm { H } ^ { + } \right]$ . The pH scale ranges from 0 to 14 . Pure water is taken as neutral having a $\mathrm { pH }$ of 7 . A pH less than 7 is acidic. A pH greater than 7 is alkaline (or basic) .

Two acids have $\left[ \mathrm { H } ^ { + } \right]$ values of $3.2 \times 10 ^ { - 3 } \mathrm {~mol} / \mathrm { L }$ and $2.4 \times 10 ^ { - 6 } \mathrm {~mol} / \mathrm { L }$ respectively. Find the $\mathrm { pH }$ for each acid. Which substance is more acidic? Round $\mathrm { pH }$ values to 1 decimal place.

• A) \(2.5 ; 5.6\); The first acid is more acidic.
• B) \(5.7 ; 12.9\); The second acid is more acidic
• C) \(2.5 ; 5.6\); The second acid is more acidic.
• D) \(5.7 ; 12.9\); The first acid is more acidic.

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Definitions:

-logy

A suffix used to indicate the study or science of a particular subject.

Milliliter

A metric unit of volume equal to one-thousandth of a liter, commonly used to measure liquids.

Thousandth

A unit or measure representing one part in a thousand of something.

Liter

A metric unit of volume equal to 1000 cubic centimeters or approximately 0.26 U.S. gallons.