Problem 37 - Chemistry: The Central Science

Question

Which of these statements about alloys and intermetallic compounds is false? (a) Bronze is an example of an alloy. (b) "Alloy" is just another word for "a chemical compound of fixed composition that is made of two or more metals." (c) Intermetallics are compounds of two or more metals that have a definite composition and are not considered alloys. (d) If you mix two metals together and, at the atomic level, they separate into two or more different compositional phases, you have created a heterogeneous alloy. (e) Alloys can be formed even if the atoms that comprise them are rather different in size.

Step-by-Step Solution

Answer

The false statement is (b) "Alloy is just another word for a chemical compound of fixed composition that is made of two or more metals." Alloys have variable compositions and are not restricted to fixed compositions like chemical compounds.

Step 1: Understanding Alloys and Intermetallic Compounds

Alloys are metallic materials composed of two or more elements, usually metals, which are combined to enhance or modify their properties. Intermetallic compounds, on the other hand, are solid-state compounds that consist of two or more metallic elements with a fixed stoichiometry and ordered crystal structure.

Step 2: Analyzing Each Statement

(a) Bronze is an example of an alloy. Bronze is a well-known alloy, typically made by combining copper and tin. This statement is true. (b) "Alloy" is just another word for "a chemical compound of fixed composition that is made of two or more metals." Alloys have variable compositions and are not restricted to fixed compositions like chemical compounds. This is the false statement. (c) Intermetallics are compounds of two or more metals that have a definite composition and are not considered alloys. Intermetallic compounds have a fixed stoichiometry and ordered crystal structure, distinguishing them from alloys. This statement is true. (d) If you mix two metals together and, at the atomic level, they separate into two or more different compositional phases, you have created a heterogeneous alloy. A heterogeneous alloy consists of multiple phases with different compositions. Mixing two metals that separate into different compositional phases creates a heterogeneous alloy. This statement is true. (e) Alloys can be formed even if the atoms that comprise them are rather different in size. The size difference between the constituent atoms of an alloy can lead to unique properties and the formation of various types of solid solutions. Thus, this statement is also true.

Step 3: Conclusion

Based on the analysis, statement (b) "Alloy is just another word for a chemical compound of fixed composition that is made of two or more metals." is false. This is because alloys have variable compositions and are not restricted to fixed compositions like chemical compounds.