Problem 42 - Chemistry: The Central Science

Question

Indicate whether each statement is true or false: (a) Intermetallic compounds have a fixed composition. (b) Copper is the majority component in both brass and bronze. (c) In stainless steel, the chromium atoms occupy interstitial positions.

Step-by-Step Solution

Answer

(a) True: Intermetallic compounds have a fixed composition with a well-defined crystal structure. (b) True: Copper is the majority component in both brass (copper-zinc alloy) and bronze (copper-tin alloy). (c) False: In stainless steel, chromium atoms act as a substitutional alloying element, not occupying interstitial positions.

Step 1: Statement (a) analysis

Intermetallic compounds are formed by the combination of two or more metallic elements in a specific ratio, and they have a well-defined crystal structure. Thus, they do have a fixed composition. So, statement (a) is true.

Step 2: Statement (b) analysis

Brass and bronze are both metal alloys that mainly consist of copper. Brass is made from a combination of copper and zinc, with copper being the majority component. Bronze is an alloy of copper and tin, again with copper as the majority component. Hence, statement (b) is true.

Step 3: Statement (c) analysis

Stainless steel is a metal alloy composed of iron, chromium, nickel, and small amounts of other elements. Chromium is added to stainless steel to form a thin, invisible, and passive layer of chromium oxide on the surface, which provides corrosion resistance. However, chromium does not occupy interstitial positions in the crystal lattice; it substitutes some of the iron atoms and is present as a substitutional alloying element. Therefore, statement (c) is false.