properties of acids

what are acids

Acids are ionic compounds that produce positive hydrogen ions (H+ ) when dissolved in water. Ionic compounds are compounds that contain positive metal ions and negative nonmetal ions held together by ionic bonds. (Ions are atoms that have become charged particles by gaining or losing electrons.) An example of an acid is hydrogen chloride (HCl). When it dissolves in water, it separates into positive hydrogen ions and negative chloride ions (Cl ). This is represented by the chemical equation: H O 2 HCl H+ + Cl

strength of acids

The strength of acids is measured on a scale called the pH scale. The pH value of a solution represents its concentration of hydrogen ions. A pH value of 7 indicates a neutral solution, and a pH value less than 7 indicates an acidic solution. The lower the pH value is, the greater is the concentration of hydrogen ions and the stronger the acid. The strongest acids, such as battery acid, have pH values close to zero.

uses of acids

Acids have many important uses, especially in industry. For example, sulfuric acid is used to manufacture a variety of different products, including paper, paint, and detergent. Some other uses of acids are be seen in the Figure 1.3.


properties of acids

You already know that a sour taste is one property of acids. (Warning: Never taste an unknown substance to see whether it is an acid!) Acids have certain other properties as well. For example, acids can conduct electricity when dissolved in water because they consist of charged particles in solution. (Electric current is a flow of charged particles.) Acids can also react with metals, and when they do they produce hydrogen gas. An example of this type of reaction is hydrochloric acid reacting with the metal zinc (Zn). The reaction is pictured in the Figure 1.1. It can be represented by the chemical equation: Zn + 2HCl H2 + ZnCl2 Q: What sign indicates that a gas is being produced in this reaction? A: The bubbles are hydrogen gas rising through the acid. Q: Besides hydrogen gas, what else is produced in this reaction? A: This reaction also produces zinc chloride ZnCl2 , which is a neutral ionic compound called a salt.


detecting acids

Certain compounds, called indicators, change color when acids come into contact with them, so indicators can be used to detect acids. An example of an indicator is the compound called litmus. It is placed on small strips of paper that may be red or blue. If you place a few drops of acid on a strip of blue litmus paper, the paper will turn red. You can see this in the Figure 1.2. Litmus isnt the only indicator for detecting acids. Red cabbage juice also works well, as you can see in this entertaining video. Click image to the left or use the URL below. URL: Drawing of blue litmus paper turning red in acid.


instructional diagrams

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an example of an acid is hcl.

-->  a. true

b. false

all acids taste sour.

-->  a. true

b. false

when acids react with metals, they produce

a) hydrogen gas.

b) a salt.

c) a base.

-->  d) two of the above

which statement about ph is true?

a) a neutral solution has a ph of 0.

b) an acid has a ph greater than 7.

-->  c) an acid has a ph less than 7.

d) a very weak acid has a ph close to 0.

litmus paper is the only indicator of acids.

a. true

-->  b. false

diagram questions

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