21. Which gas is released during cement manufacture?
A) O₂
B) CO₂
C) H₂
D) N₂
Answer: B
22. Glass is mainly composed of:
A) SiO₂
B) CaCO₃
C) NaCl
D) Al₂O₃
Answer: A
23. Which is used as flux in glass manufacture?
A) Na₂CO₃
B) CaO
C) SiO₂
D) Al₂O₃
Answer: A
24. Steel is an alloy of:
A) Iron and carbon
B) Iron and copper
C) Copper and zinc
D) Aluminum and iron
Answer: A
25. Which furnace is used for iron extraction?
A) Blast furnace
B) Electric furnace
C) Reverberatory furnace
D) Bessemer converter
Answer: A
26. Coke is used in blast furnace as:
A) Fuel
B) Reducing agent
C) Both A and B
D) None
Answer: C
27. The main ore of iron is:
A) Bauxite
B) Hematite
C) Galena
D) Zinc blende
Answer: B
28. Which industry produces fertilizers?
A) Petrochemical
B) Agrochemical
C) Metallurgical
D) Textile
Answer: B
29. Urea is a:
A) Nitrogen fertilizer
B) Phosphate fertilizer
C) Potash fertilizer
D) Organic solvent
Answer: A
30. Which acid is used in fertilizer production?
A) HCl
B) HNO₃
C) H₂SO₄
D) All of these
Answer: D