Question

An alloy of Cu and Au will show complete miscibility as per Hume-Rothery if: (A) The metallic radii of the Cu and Au differs only by 12.5%.
(B) Cu and Au have the same crystal structure.
(C) The chemical properties of both the metals are similar.
(D) The number of valence electrons is different in both.

• A. (A), (B) and (D) only
• B. (A), (B) and (C) only
• C. (A), (B), (C) and (D)
• D. (B), (C) and (D) only

Hint:

The Hume-Rothery rules are important for determining the miscibility of metals in alloys. Key factors include atomic radii, crystal structure, and chemical properties.

Answer 1

The Correct Option is B

Step 1: Hume-Rothery Rules.
The Hume-Rothery rules help determine the conditions under which two metals will form a solid solution (miscibility in alloys). The key criteria are: 1. The atomic radii of the two metals should not differ by more than 12.5%. 2. The metals must have the same crystal structure. 3. The chemical properties of the metals should be similar.

Step 2: Analyze the Options.
- (A) The metallic radii of Cu and Au differ by only 12.5%, satisfying the first condition. - (B) Cu and Au have the same crystal structure, satisfying the second condition. - (C) The chemical properties of both metals are similar, satisfying the third condition. - (D) The number of valence electrons does not significantly impact the miscibility in this case.

Step 3: Conclusion.
Thus, the correct answer is option (2): (A), (B) and (C) only.