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Amphoteric Nature of aluminium , zinc, and lead - metals, oxides, and hydroxides

Amphoteric Nature

Amphoteric substances react with both acids and bases, acting as acids with bases (accepting OH⁻) and as bases with acids (donating OH⁻ or accepting H⁺). Aluminium, zinc, and lead (to a lesser extent) exhibit this property in their metals, oxides, and hydroxides.

Summary

Aluminium: Metal, oxide, and hydroxide react readily with NaOH (forming aluminates) and HCl (forming chlorides), showing strong amphoterism.
Zinc: Similar to aluminium, forms zincates with NaOH and chlorides with HCl, though metal requires concentrated alkali.
Lead: Oxide and hydroxide are amphoteric, forming plumbites with NaOH and chlorides with HCl; metal is less reactive with NaOH.

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DETAILS

1. Aluminium (Al)

Aluminium Metal

With NaOH: Reacts to form sodium aluminate and hydrogen gas: $2Al(s) + 2NaOH(aq) + 6H₂O(l) \rightarrow 2NaAl(OH)₄(aq) + 3H₂(g)$
With Dilute HCl: Forms aluminium chloride: $2Al(s) + 6HCl(aq) \rightarrow 2AlCl₃(aq) + 3H₂(g)$

Aluminium Oxide (Al₂O₃)

With NaOH: Dissolves to form sodium aluminate: $Al₂O₃(s) + 2NaOH(aq) + 3H₂O(l) \rightarrow 2NaAl(OH)₄(aq)$
With Dilute HCl: Forms aluminium chloride: $Al₂O₃(s) + 6HCl(aq) \rightarrow 2AlCl₃(aq) + 3H₂O(l)$

Aluminium Hydroxide (Al(OH)₃)

With NaOH: Dissolves to form sodium aluminate: $Al(OH)₃(s) + NaOH(aq) \rightarrow NaAl(OH)₄(aq)$
With Dilute HCl: Forms aluminium chloride: $Al(OH)₃(s) + 3HCl(aq) \rightarrow AlCl₃(aq) + 3H₂O(l)$

2. Zinc (Zn)

Zinc Metal

With NaOH: Reacts in hot, concentrated NaOH to form sodium zincate: $Zn(s) + 2NaOH(aq) + 2H₂O(l) \rightarrow Na₂Zn(OH)₄(aq) + H₂(g)$
With Dilute HCl: Forms zinc chloride: $Zn(s) + 2HCl(aq) \rightarrow ZnCl₂(aq) + H₂(g)$

Zinc Oxide (ZnO)

With NaOH: Forms sodium zincate: $ZnO(s) + 2NaOH(aq) + H₂O(l) \rightarrow Na₂Zn(OH)₄(aq)$
With Dilute HCl: Forms zinc chloride: $ZnO(s) + 2HCl(aq) \rightarrow ZnCl₂(aq) + H₂O(l)$

Zinc Hydroxide (Zn(OH)₂)

With NaOH: Dissolves to form sodium zincate: $Zn(OH)₂(s) + 2NaOH(aq) \rightarrow Na₂Zn(OH)₄(aq)$
With Dilute HCl: Forms zinc chloride: $Zn(OH)₂(s) + 2HCl(aq) \rightarrow ZnCl₂(aq) + 2H₂O(l)$

3. Lead (Pb)

Lead Metal

With NaOH: Does not react significantly under standard conditions.
With Dilute HCl: Reacts slowly due to insoluble PbCl₂ formation: $Pb(s) + 2HCl(aq) \rightarrow PbCl₂(s) + H₂(g)$

Lead(II) Oxide (PbO)

With NaOH: Forms sodium plumbite: $PbO(s) + 2NaOH(aq) + H₂O(l) \rightarrow Na₂Pb(OH)₄(aq)$
With Dilute HCl: Forms lead(II) chloride (sparingly soluble): $PbO(s) + 2HCl(aq) \rightarrow PbCl₂(s) + H₂O(l)$

Lead(II) Hydroxide (Pb(OH)₂)

With NaOH: Dissolves to form sodium plumbite: $Pb(OH)₂(s) + 2NaOH(aq) \rightarrow Na₂Pb(OH)₄(aq)$
With Dilute HCl: Forms lead(II) chloride: $Pb(OH)₂(s) + 2HCl(aq) \rightarrow PbCl₂(s) + 2H₂O(l)$

Special action of Ammonium Hydroxide on solutions of copper salts and sodium hydroxide on ammonium salts

Special action of Ammonium Hydroxide on solutions of copper salts and sodium hydroxide on ammonium salts

>>> When ammonium hydroxide is added to solutions of copper salts, it produces a unique deep blue solution.

>>> Similarly, when sodium hydroxide is mixed with ammonium salts and heated, it generates ammonia gas.

Part 1: "Special action of Ammonium Hydroxide on solutions of copper salts"

Ammonium Hydroxide (NH₄OH): This is a solution of ammonia (NH₃) in water, often used in chemistry labs. It acts as a base and can form complexes with certain metals.
Solutions of copper salts: These are liquids containing dissolved copper compounds, like copper sulfate (CuSO₄) or copper chloride (CuCl₂). Copper salts usually contain copper(II) ions (Cu²⁺).
Special action: When you add ammonium hydroxide to a copper salt solution, something unique happens:
1. First step: A pale blue solid (precipitate) forms, called copper(II) hydroxide (Cu(OH)₂). This shows copper is present.
  - Example: CuSO₄ + 2NH₄OH → Cu(OH)₂ (blue solid) + (NH₄)₂SO₄
2. Second step: If you add more ammonium hydroxide, the blue solid dissolves, and the solution turns a bright, deep blue color. This is because a new compound forms, called tetraamminecopper(II) complex ([Cu(NH₃)₄]²⁺).
  - Example: Cu(OH)₂ + 4NH₃ → [Cu(NH₃)₄]²⁺ (deep blue solution) + 2OH⁻
Why it matters: This deep blue color is a clear sign of copper(II) ions, so chemists use this reaction to test for copper in a sample.

Part 2: "Sodium hydroxide on ammonium salts"

Sodium Hydroxide (NaOH): This is a strong base, often called caustic soda, used in many chemical reactions.
Ammonium salts: These are compounds containing the ammonium ion (NH₄⁺), like ammonium chloride (NH₄Cl) or ammonium sulfate ((NH₄)₂SO₄).
Action: When you mix sodium hydroxide with an ammonium salt and gently heat the mixture, it produces ammonia gas (NH₃), which you can smell (it’s sharp and pungent).
- Example reaction: NH₄Cl + NaOH → NaCl + H₂O + NH₃↑ (ammonia gas)
Why it matters: The smell of ammonia gas confirms the presence of ammonium ions in the salt. Chemists use this as a test to detect ammonium in a sample.

Putting It Together

The statement describes two separate chemical tests:
1. Ammonium hydroxide + copper salts → Forms a deep blue solution, proving copper is present.
2. Sodium hydroxide + ammonium salts → Releases ammonia gas when heated, proving ammonium is present.
These are "special" because they give clear, recognizable results (color change or gas) that help identify specific chemicals in a lab.

“Hibernal” by Babette Deutsch

This poem paints a vivid and stark portrait of winter, not just as a season of the year, but as a metaphor for human mortality, struggle, and the inexorable passage of time. Here's a breakdown of its themes and imagery:

1. The park as a symbol of desolation:

"The park is winter-plucked. The sky / and the grey pavement show a sheeted face"
Winter strips life from the park, leaving it barren and lifeless. The "sheeted face" evokes an image of death, as a sheet often covers a corpse, symbolizing the inevitability of mortality. The park's lifelessness mirrors the "covered stare of one who had to die," emphasizing the universality of death and the silence it imposes.

2. Human labor and futility:

"Now, when men sweat, / shoveling muddy snow or heaving ice, / they know the helpless sweat that will not wet them twice"
The act of labor—shoveling snow, a repetitive and seemingly endless task—is likened to life's struggles. The "helpless sweat" suggests that these efforts are ultimately futile in the grand scheme of life and death, as they do not yield enduring results. The line captures the fragility and impermanence of human exertion.
"They know the staggering heart, the smothered breath / that stand between this knowing and the end"
This describes the physical toll of both labor and existential awareness. The "staggering heart" and "smothered breath" reflect the proximity of life's limits—the bodily reminders of mortality.

3. The heaviness of time:

"Though they must drag a net of heavy hours / about their straining limbs"
Time is depicted as a burdensome net that traps and weighs individuals down, making their struggles even more arduous. Yet, this burden is finite—it will eventually "break" as time runs out.

4. Transience of love and faith:

"Love like a pillar of cloud, a pillar of fire— / this net will break before they tire, / this cloud, this flame will vanish and be cold"
The reference to the "pillar of cloud" and "pillar of fire" draws from the biblical Exodus story, where God guided the Israelites through the wilderness. Here, it suggests love or faith as a guiding force in life. However, the poet warns that these too are transient, destined to "vanish and be cold," leaving behind only emptiness.

5. The unyielding return of winter and mortality:

"Winter is on us now, and will return: / soiled snows will choke the city streets again"
Winter, a cyclical season, becomes a metaphor for death and hardship, which also recur endlessly. The "soiled snows" evoke decay and corruption, suggesting that life's struggles and losses are inevitable and will always resurface.
"Bleak twilights dull the windows as before, / dark hurrying crowds push towards lit rooms in vain"
The imagery of "bleak twilights" and "dark hurrying crowds" captures the futility of human attempts to escape the cold, literal and metaphorical. The "lit rooms" promise warmth and comfort, yet the attempt to reach them is described as "in vain," emphasizing existential despair.

6. The finality of life:

"One day we shall not kiss or quarrel any more"
The poem concludes with an acknowledgment of life's ultimate endpoint. The simple acts of love and conflict—hallmarks of human connection—will cease, leaving only silence.

Interpretation:

The poem portrays winter as a powerful symbol of death, struggle, and the inevitable cycles of life. It reflects on the physical and emotional toll of existence, while emphasizing the transience of human efforts, emotions, and relationships. The cold, unrelenting imagery serves as a reminder of mortality, and yet there is a somber beauty in its acknowledgment of the shared human experience of striving against this inevitability.

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The park is winter-plucked. The sky
and the grey pavement show a sheeted face:
the covered stare of one who had to die.
Now, when men sweat,
shoveling muddy snow or heaving ice,
they know the helpless sweat that will not wet them twice,
they know the staggering heart, the smothered breath
that stand between this knowing and the end.
Though they must drag a net of heavy hours
about their straining limbs,
though they behold
love like a pillar of cloud, a pillar of fire—
this net will break before they tire,
this cloud, this flame will vanish and be cold.
Men think of this who limp against the wind
that freezes hate and sucks at their desire.
Winter is on us now, and will return:
soiled snows will choke the city streets again,
bleak twilights dull the windows as before,
dark hurrying crowds push towards lit rooms in vain.
One day we shall not kiss or quarrel any more.