Worksheet on the Reactivity Series with Answers, covering metal reactivity, chemical equations, and displacement reactions.

You’ve uploaded a completed worksheet on the Reactivity Series of Metals, with handwritten answers filled in. I’ll now solve and explain each question as if you were asking for a full walkthrough — even though the answers are already written, I’ll clarify *why* they’re correct and provide deeper explanations.

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## 🔹 Question 1: Answer the following questions

a) Why does gold occur native (uncombined) whereas zinc does not?

✔ Answer:
Gold is an unreactive (inert) metal which will not readily combine with other elements and will not oxidize. Unlike zinc, which is more reactive and can easily react with other elements and oxidize to Zinc Oxide.

🧠 Explanation:
The reactivity series ranks metals by how readily they lose electrons (oxidize). Gold is near the bottom — very unreactive. It doesn’t corrode or react with air/water/acid under normal conditions, so it’s found pure (“native”) in nature. Zinc, higher up, reacts easily with oxygen and acids, forming compounds like ZnO or ZnCl₂ — so it’s never found native.

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b) Why was silver used to make coins in the past?

✔ Answer:
Silver is a rare metal, making it valuable to make coins; relatively unreactive.

🧠 Explanation:
Coins need to be durable (not corrode), recognizable (valuable), and easy to mint. Silver is corrosion-resistant (doesn’t tarnish easily compared to iron or copper), has intrinsic value due to rarity, and is malleable enough to shape into coins. Today, most coins are made of cheaper alloys, but historically, silver was ideal.

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c) Why is copper used to make electrical cables and wires?

✔ Answer:
Copper is abundant in nature and a very good conductor of electricity — copper is very ductile (turns into wire form).

🧠 Explanation:
Copper’s high electrical conductivity allows efficient electron flow. Its ductility means it can be drawn into thin wires without breaking. It’s also relatively inexpensive and resistant to corrosion — perfect for long-term use in wiring.

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d) Why does titanium commonly used for making space vehicles?

✔ Answer:
Titanium has many special characteristics as a durable metal with high melting point, high strength.

🧠 Explanation:
Titanium has an excellent strength-to-weight ratio — strong but lightweight. It resists extreme temperatures and corrosion (important in space environments). These properties make it ideal for aerospace applications like rockets and satellites.

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## 🔹 Question 2: Reactivity order — sodium > magnesium > zinc > copper

a) Describe what each metal does when:

#### i) Reacts with water
✔ Answer: Sodium only — making sodium hydroxide and hydrogen gas.

🧠 Explanation:
Only very reactive metals (like Na, K, Ca) react with cold water. Magnesium reacts slowly with hot water or steam. Zinc and copper don’t react with water at all under normal conditions.

> Reaction:
> `2Na + 2H₂O → 2NaOH + H₂`

#### ii) Heated in air
✔ Answer: Sodium and magnesium burn easily in air.

🧠 Explanation:
Sodium burns with a yellow flame, forming sodium oxide/peroxide. Magnesium burns with a bright white flame, forming MgO. Zinc forms a protective layer of ZnO when heated. Copper forms black CuO but doesn’t “burn” vigorously.

#### iii) Added to dilute hydrochloric acid
✔ Answer: Except copper, others react.

🧠 Explanation:
Metals above hydrogen in the reactivity series displace H⁺ from acids. So:
- Na, Mg, Zn → produce H₂ gas
- Cu → no reaction (below H)

> Example: `Zn + 2HCl → ZnCl₂ + H₂`

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b) Which metal suitable for saucepan? Why others are not?

✔ Answer: Copper — durable, unreactive to water/acids, good heat conductor.

🧠 Explanation:
Copper conducts heat evenly — great for cooking. It’s also stable (won’t corrode quickly with food acids). Sodium and magnesium are too reactive — they’d react violently with water/steam or food acids. Zinc might leach into food and is toxic in large amounts.

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## 🔹 Question 3: Magnesium ribbon in copper sulfate solution

✔ Answer:
Magnesium displaces copper because it’s more reactive.
Word equation:
Magnesium + Copper Sulfate → Magnesium Sulfate + Copper

Chemical equation:
`Mg(s) + CuSO₄(aq) → MgSO₄(aq) + Cu(s)`

🧠 Explanation:
This is a single displacement reaction. Since Mg is higher than Cu in the reactivity series, it pushes Cu²⁺ out of solution, forming solid copper (reddish deposit) and Mg²⁺ ions in solution. You’d see the blue color fade and red-brown copper coating form on the magnesium ribbon.

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## 🔹 Question 4: Complete word equations & chemical equations

Let’s go one by one:

a) Zinc + Lead Nitrate Solution →

✔ Answer: Zinc nitrate + lead
`Zn + Pb(NO₃)₂ → Zn(NO₃)₂ + Pb`

🧠 Explanation: Zn > Pb in reactivity → displacement occurs.

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b) Iron + Zinc Sulphate Solution →

✔ Answer: No reaction

🧠 Explanation: Iron is *less* reactive than zinc → cannot displace Zn²⁺.

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c) Lead + Copper Nitrate Solution →

✔ Answer: Lead nitrate + copper
`Pb + Cu(NO₃)₂ → Pb(NO₃)₂ + Cu`

🧠 Explanation: Pb > Cu → displacement happens.

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d) Magnesium + Zinc Chloride Solution →

✔ Answer: Magnesium chloride + zinc
`Mg + ZnCl₂ → MgCl₂ + Zn`

🧠 Explanation: Mg > Zn → displaces Zn.

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e) Copper + Sodium Chloride Solution →

✔ Answer: No reaction

🧠 Explanation: Cu < Na → cannot displace Na⁺.

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f) Zinc + Iron Sulphate Solution →

✔ Answer: Zinc sulphate + iron
`Zn + FeSO₄ → ZnSO₄ + Fe`

🧠 Explanation: Zn > Fe → displaces Fe.

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g) Gold + Silver Nitrate Solution →

✔ Answer: No reaction

🧠 Explanation: Au < Ag → cannot displace Ag⁺.

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h) Calcium + Magnesium Nitrate Solution →

✔ Answer: Calcium nitrate + magnesium
`Ca + Mg(NO₃)₂ → Ca(NO₃)₂ + Mg`

🧠 Explanation: Ca > Mg → displaces Mg.

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## 🔹 Question 5: Three metals X, Y, Z — determine order

Given:
- Y displaces X → Y > X
- Z displaces both X and Y → Z > Y and Z > X

✔ Answer: Least reactive → X, then Y, then Z (most reactive)

🧠 Explanation:
In displacement reactions, the more reactive metal displaces the less reactive one from its salt solution. So:
- Z can displace both → Z is most reactive
- Y displaces X → Y > X
→ Order: X < Y < Z

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## 🔹 Question 6: Mystery metals Q and R — based on reactivity series

Given series:
K > Q > Ca > Mg > Al > Zn > R > Fe > Cu

a) Will Q react with cold water? → ✔ Yes

🧠 Because Q is above Ca (which reacts with cold water), so Q must also react.

b) Will R react with cold water? → ✔ No

🧠 R is below Zn and above Fe — metals below Mg typically don’t react with cold water.

c) Will R react with dilute hydrochloric acid? → ✔ Yes

🧠 R is above H (since Fe reacts with acid, and R > Fe), so yes.

d) Will R displace copper from copper sulphate? → ✔ Yes

🧠 R > Cu → so yes, it can displace Cu²⁺.

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## 🔹 Question 7: Explain trends in reactivity

(i) Why reactivity increases down a group? (e.g., Li → Na → K)

✔ Answer: As we go down Group 1, atomic size increases → outermost electron is farther from nucleus → less attraction → easier to lose → more reactive.

🧠 Detailed explanation:
- Lithium (Li) has smallest atomic radius → strong nuclear pull on valence electron → hard to lose.
- Potassium (K) has larger radius → weaker pull → electron lost easily → more reactive.
- Also, shielding effect increases → inner electrons shield outer electron from nucleus.

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(ii) Why is Sodium more reactive than Magnesium and Aluminum?

✔ Answer: Sodium has only 1 valence electron, while Mg has 2 and Al has 3. It’s easier for an atom to lose 1 electron than 2 or 3.

🧠 Explanation:
- Ionization energy: Removing 1st electron from Na is easier than removing 1st from Mg (which has higher effective nuclear charge).
- Mg needs to lose 2 electrons to form Mg²⁺, Al needs 3 to form Al³⁺ — requires more energy.
- So Na loses its electron most easily → highest reactivity among these three.

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## 🧾 Final Notes:

This worksheet covers key concepts:
- Reactivity series ordering
- Displacement reactions
- Reaction with water, air, acids
- Trends in periodic table (group and period)
- Practical applications (coins, wires, cookware, spacecraft)

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