For common soda–lime window glass used in buildings and glazing, what is the typical percentage range of silica (SiO2) in its composition? Select the most appropriate range widely cited in practice.

Introduction / Context:
Soda–lime glass dominates window glazing. Its properties (softening temperature, durability, workability) are governed by the relative amounts of silica, soda, and lime. Remembering the SiO2 band helps in material identification and quality discussions with vendors and site staff.

Given Data / Assumptions:

• Glass type: soda–lime (typical float glass).
• We seek the silica fraction only.
• Ranges are approximate but reflect standard recipes.

Concept / Approach:

Soda–lime glass generally contains a high proportion of silica as the network former. Typical nominal compositions cluster around SiO2 ≈ 70–74%, Na2O ≈ 12–16%, CaO ≈ 8–12%, with small MgO/Al2O3. Thus, the best choice among discrete ranges is 70% to 75%.

Step-by-Step Solution:

Verification / Alternative check:

Manufacturer datasheets for architectural float glass consistently report silica near 72%, confirming the range.

Why Other Options Are Wrong:

Lower ranges (40–65%) underestimate the network former for soda–lime glass; 80–85% is typical of special high-silica glasses, not standard window glass.

Common Pitfalls:

Mixing up fused silica (very high SiO2) with soda–lime compositions; overlooking flux (soda) and stabilizer (lime) fractions.

Final Answer:

70% to 75%