Ch.4 - Reactions in Aqueous Solution

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.4 - Reactions in Aqueous Solution

Problem 94

Chapter 4, Problem 94

Assume that you are given a solution of an unknown acid or base. How can you tell whether the unknown substance is acidic or basic?

Verified step by step guidance

insert step 1> Determine the pH of the solution using a pH meter or pH paper.

insert step 2> Compare the pH value to the neutral pH of 7.

insert step 3> If the pH is less than 7, the solution is acidic.

insert step 4> If the pH is greater than 7, the solution is basic.

insert step 5> If the pH is exactly 7, the solution is neutral, indicating neither acidic nor basic properties.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. A pH less than 7 indicates an acidic solution, while a pH greater than 7 indicates a basic solution. A pH of exactly 7 is considered neutral, typical of pure water. Understanding the pH scale is essential for determining the nature of the unknown substance.

Indicators

Indicators are substances that change color in response to the pH of a solution, providing a visual means to determine whether a solution is acidic or basic. Common indicators include litmus paper, which turns red in acidic solutions and blue in basic ones, and phenolphthalein, which is colorless in acidic solutions and pink in basic ones. Using indicators is a practical method for identifying the nature of the unknown substance.

Acid-Base Theory

Acid-base theory encompasses various definitions, including the Arrhenius, Brønsted-Lowry, and Lewis theories, which describe acids as proton donors and bases as proton acceptors. Understanding these theories helps in predicting the behavior of the unknown substance in reactions and its interaction with water. This theoretical framework is crucial for classifying the unknown substance as either an acid or a base.

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02:08

Bronsted-Lowry Acid-Base Theory

Related Practice

Textbook Question

Why do we use a double arrow to show the dissociation of a weak acid or weak base in aqueous solution?

Textbook Question

Write balanced ionic equations for the following reactions. (a) Aqueous perchloric acid is neutralized by aqueous calcium hydroxide.

Textbook Question

The following three solutions are mixed: 100.0 mL of 0.100 M Na2SO4, 50.0 mL of 0.300 M ZnCl2, and 100.0 mL of 0.200 M Ba(CN)2. (b) What is the molarity of each ion remaining in the solution assuming complete precipitation of all insoluble compounds?

Textbook Question

A 250.0 g sample of a white solid is known to be a mixture of KNO3, BaCl2, and NaCl. When 100.0 g of this mixture is dis-solved in water and allowed to react with excess H2SO4, 67.3 g of a white precipitate is collected. When the remaining 150.0 g of the mixture is dissolved in water and allowed to react with excess AgNO3, 197.6 g of a second precipitate is collected. (a) What are the formulas of the two precipitates?

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Textbook Question

(b) What is the mass of each substance in the original 250 g mixture?

Textbook Question

Write balanced ionic equations for the following reactions. (b) Aqueous sodium hydroxide is neutralized by aqueous acetic acid.