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Answer: Metals react with oxygen to form metal oxides, but their reactivity varies. Sodium (Na) is highly reactive and combines rapidly with oxygen, often catching fire in air. It forms sodium oxide (Na₂O): 4Na + O₂ → 2Na₂O. Sodium is so reactive that it is stored under kerosene to avoid contact with oxygen and moisture. Magnesium (Mg) burns with a bright white flame, forming magnesium oxide (MgO): 2Mg + O₂ → 2MgO. This is a typical demonstration in labs using a clean Mg ribbon. Iron (Fe) requires strong heating to react with oxygen and forms magnetite (Fe₃O₄): 3Fe + 2O₂ → Fe₃O₄, which appears blackish. Most metal oxides are basic, and some can be amphoteric. Observations include flame, heat, and solid oxide formation, differing due to each metal’s reactivity.
Answer: Metals react with water to form hydroxides (with cold or hot water) or oxides (with steam) and release hydrogen gas (H₂). Sodium (Na) and potassium (K) react explosively even with cold water, forming strong bases and H₂: 2Na + 2H₂O → 2NaOH + H₂, 2K + 2H₂O → 2KOH + H₂. This reaction is so vigorous that the hydrogen may catch fire. Calcium (Ca) reacts vigorously (but not explosively) with cold water: Ca + 2H₂O → Ca(OH)₂ + H₂, producing bubbles; calcium often floats due to H₂ sticking to its surface. Magnesium (Mg) reacts very slowly with cold water, faster with hot water: Mg + 2H₂O (hot) → Mg(OH)₂ + H₂, and fastest with steam: Mg + H₂O (steam) → MgO + H₂. Less reactive metals like zinc and iron react only with steam, while copper, silver, gold do not react with water at all.
Answer: Metals react with dilute acids (like HCl, H₂SO₄) to form a salt and hydrogen gas (H₂). The general rule is: Metal + Acid → Salt + Hydrogen. For example, zinc reacts briskly with hydrochloric acid: Zn + 2HCl → ZnCl₂ + H₂, producing bubbles and warming the test tube. Magnesium reacts rapidly with sulphuric acid: Mg + H₂SO₄ → MgSO₄ + H₂, with noticeable fizzing and a quick decrease in the metal strip size. Iron reacts more slowly: Fe + 2HCl → FeCl₂ + H₂. Metals like copper, silver, and gold do not react with dilute acids because they are less reactive than hydrogen and cannot displace it. A ‘pop’ sound confirms hydrogen when a burning matchstick is brought near the mouth of the test tube. The rate depends on the metal’s position in the reactivity series.
Answer: A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its salt solution. This is guided by the reactivity series. When an iron nail is dipped in copper sulphate (CuSO₄), iron displaces copper: Fe + CuSO₄ → FeSO₄ + Cu. The blue solution turns green (FeSO₄), and a reddish-brown copper layer appears on the nail. Similarly, zinc displaces copper: Zn + CuSO₄ → ZnSO₄ + Cu, and the blue fades toward colourless (ZnSO₄ forms). Magnesium is more reactive than zinc, so it displaces zinc from zinc sulphate: Mg + ZnSO₄ → MgSO₄ + Zn, producing a grey deposit of zinc. These reactions visually reinforce that a stronger (more reactive) metal can push a weaker metal out of its compound in solution.
Answer: Choose calcium (Ca) for a safe and clear demonstration of metal reaction with cold water. Calcium reacts vigorously but not explosively, producing calcium hydroxide and hydrogen gas: Ca + 2H₂O → Ca(OH)₂ + H₂. Procedure: take a beaker with cold water, drop a small piece of calcium, and observe bubbling. The metal may float due to hydrogen bubbles. Test the evolved gas with a burning matchstick for a soft ‘pop’ indicating H₂. Dip blue litmus into the water after reaction; it turns blue, showing the formation of basic Ca(OH)₂. Precautions: use small quantities, keep face away, and do not use highly reactive metals like sodium or potassium (they are explosive with water). This experiment clearly shows the trend in reactivity and formation of a base in water reactions.
Answer:
Answer: This is a displacement reaction where iron, being more reactive than copper, displaces copper from copper sulphate. The reaction is: Fe + CuSO₄ → FeSO₄ + Cu. The blue color of CuSO₄ changes to green due to formation of iron sulphate (FeSO₄). The brown coating on the nail is copper metal. To confirm products: filter and scrape the coating, then gently rub it—its reddish-brown color and metallic luster confirm copper. Test the solution with potassium ferricyanide (if available) to see a color change indicating Fe²⁺ (extension). Alternatively, compare the solution’s color with a known FeSO₄ sample. Rinse the nail in dilute acid to remove loosely adhered Cu and weigh before and after to see mass increase due to copper deposition, supporting the displacement explanation.
Answer: Potassium is extremely reactive. On contact with water, you’ll observe violent fizzing, rapid heat production, and hydrogen gas (H₂) evolving so fast that it may ignite, producing a flame and possibly small explosions. The reaction is: 2K + 2H₂O → 2KOH + H₂. Immediate steps:
Answer: Step 1: Add a zinc strip to Solution A.
Step 2: Confirm with iron in the suspected CuSO₄.
Step 3: Use magnesium against the suspected ZnSO₄.
Logic: A more reactive metal displaces a less reactive one. Mg > Zn > Fe > Cu in reactivity, so choose pairs that should react and observe color changes and deposits to label the solutions confidently.
Answer: Reaction rates align with the reactivity series and the reaction conditions. Sodium (Na) is highly reactive; it donates electrons readily, and with cold water forms NaOH and H₂ so quickly that heat ignites hydrogen, causing explosive behavior. Magnesium (Mg) is less reactive than Na, so with cold water it reacts very slowly, but hot water increases particle energy and steam drives the reaction efficiently to form MgO and H₂. Iron (Fe) is further down the series relative to Mg, so with dilute acids it reacts slowly, producing FeCl₂ (or FeSO₄) and H₂, with fewer bubbles and less heat compared to Mg or Zn. Observations—explosive fizzing (Na), gentle bu...