`20 multiple-choice questions (MCQs) about chemistry` --- 1. **What is the chemical symbol for water?** A) *H₂O* 💧 B) *CO₂* 🌫️ C) *O₂* 🌬️ D) *NaCl* 🧂 **Answer:** `A) H₂O 💧` 2. **Which element has the atomic number 1?** A) *Helium* 🎈 B) *Hydrogen* 🚀 C) *Oxygen* 🌬️ D) *Carbon* 🔥 **Answer:** `B) Hydrogen 🚀` 3. **What is the pH of a neutral solution?** A) *0* 🔴 B) *7* 🟢 C) *14* 🔵 D) *10* 🟡 **Answer:** `B) 7 🟢` 4. **Which gas is most abundant in Earth's atmosphere?** A) *Oxygen* 🌬️ B) *Carbon Dioxide* 🌫️ C) *Nitrogen* 🌍 D) *Argon* ⚡ **Answer:** `C) Nitrogen 🌍` 5. **What is the main component of natural gas?** A) *Methane* 🔥 B) *Ethane* ⛽ C) *Propane* � D) *Butane* � **Answer:** `A) Methane 🔥` 6. **Which of the following is a noble gas?** A) *Helium* 🎈 B) *Chlorine* 🧪 C) *Fluorine* ⚡ D) *Bromine* 🟤 **Answer:** `A) Helium 🎈` 7. **What is the chemical formula for table salt?** A) *NaCl* 🧂 B) *H₂SO₄* 🧪 C) *NaOH* 🔥 D) *KCl* ⚡ **Answer:** `A) NaCl 🧂` 8. **Which element is known as the "king of chemicals"?** A) *Oxygen* 🌬️ B) *Hydrogen* 🚀 C) *Sulfur* 🟡 D) *Sulfuric Acid* 🧪 **Answer:** `D) Sulfuric Acid 🧪` 9. **What is the smallest unit of an element?** A) *Molecule* 🔬 B) *Atom* ⚛️ C) *Compound* 🧪 D) *Ion* ⚡ **Answer:** `B) Atom ⚛️` 10. **Which of the following is a halogen?** A) *Fluorine* ⚡ B) *Neon* 💡 C) *Argon* 🌬️ D) *Krypton* 🦸 **Answer:** `A) Fluorine ⚡` 11. **What is the chemical formula for glucose?** A) *C₆H₁₂O₆* 🍬 B) *H₂O* 💧 C) *CO₂* 🌫️ D) *NaCl* 🧂 **Answer:** `A) C₆H₁₂O₆ 🍬` 12. **Which metal is liquid at room temperature?** A) *Mercury* 🌡️ B) *Iron* 🛠️ C) *Gold* 🏅 D) *Aluminum* ✈️ **Answer:** `A) Mercury 🌡️` 13. **What is the atomic number of carbon?** A) *6* 🔢 B) *12* 🔟 C) *14* 🔟 D) *8* 🔢 **Answer:** `A) 6 🔢` 14. **Which gas is responsible for the greenhouse effect?** A) *Oxygen* 🌬️ B) *Nitrogen* 🌍 C) *Carbon Dioxide* 🌫️ D) *Hydrogen* 🚀 **Answer:** `C) Carbon Dioxide 🌫️` 15. **What is the chemical symbol for gold?** A) *Ag* 🥈 B) *Au* 🥇 C) *Fe* 🛠️ D) *Cu* 🔌 **Answer:** `B) Au 🥇` 16. **Which of the following is a strong acid?** A) *Vinegar* 🍶 B) *Lemon Juice* 🍋 C) *Hydrochloric Acid* 🧪 D) *Water* 💧 **Answer:** `C) Hydrochloric Acid 🧪` 17. **What is the process of converting a liquid to a gas called?** A) *Condensation* 🌧️ B) *Evaporation* ☀️ C) *Sublimation* ❄️ D) *Freezing* 🧊 **Answer:** `B) Evaporation ☀️` 18. **Which element is essential for combustion?** A) *Nitrogen* 🌍 B) *Oxygen* 🌬️ C) *Carbon* 🔥 D) *Hydrogen* 🚀 **Answer:** `B) Oxygen 🌬️` 19. **What is the chemical formula for sulfuric acid?** A) *H₂SO₄* 🧪 B) *HCl* ⚡ C) *NaOH* 🔥 D) *NaCl* 🧂 **Answer:** `A) H₂SO₄ 🧪` 20. **Which of the following is a transition metal?** A) *Iron* 🛠️ B) *Sodium* ⚡ C) *Calcium* 🦴 D) *Potassium* 🍌 **Answer:** `A) Iron 🛠️` ---