Q21. What is the formula of ammonia?
Correct: NH3
Ammonia has the formula NH3.
Q22. Which acid is in the human stomach?
Correct: Hydrochloric acid
Hydrochloric acid helps digestion.
Q23. What is the chemical symbol for gold?
Correct: Au
Gold's symbol is Au.
Q24. Which compound gives hardness to water?
Correct: Calcium carbonate
Calcium and magnesium salts cause hardness.
Q25. What is the atomic number of hydrogen?
Correct: 1
Hydrogen has one proton.
Q26. Which metal is used in batteries?
Correct: Lithium
Lithium is widely used in batteries.
Q27. What is the formula of carbon dioxide?
Correct: CO2
Carbon dioxide contains one carbon and two oxygen atoms.
Q28. Which element is needed for respiration?
Correct: Oxygen
Oxygen is required for breathing.
Q29. What is the main component of air?
Correct: Nitrogen
Nitrogen makes up about 78% of air.
Q30. Which gas turns limewater milky?
Correct: Carbon dioxide
CO2 forms calcium carbonate in limewater.
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