Which of the following represents a chemical change? MCQ with Answer and Explanation

Explanation:
Germanium (Ge) is a metalloid, exhibiting properties of both metals and non-metals. It is a semiconductor used in transistors. Sodium and aluminium are metals. Chlorine is a non-metal. Metalloids are located along the zigzag line in the p-block.

Explanation:
Sodium bicarbonate (NaHCO₃), baking soda, is a mild base that neutralizes excess stomach acid (HCl) providing relief from acidity. Reaction: NaHCO₃ + HCl → NaCl + H₂O + CO₂. It is a component of many antacid formulations. Sodium chloride is table salt, ammonium chloride is not safe, and calcium sulfate is plaster of Paris ingredient. Milk of magnesia (Mg(OH)₂) is also an antacid.

Explanation:
Graham's law: r ∝ 1/√M. If rA = rB, then MA = MB (at same T,P). Different gases can have same molar mass (e.g., N₂ and CO both 28).