Activity 10 Aluminum Properties Quiz

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Questions and Answers

What happens to chromium in the presence of atmospheric oxygen?

It forms hydrogen gas

It gets partly or wholly oxidized to the tervalent state (correct)

It renders chromium passive

It dissolves readily in hot, concentrated H2SO4

Which type of ions does chromium form in aqueous solutions?

Cr2+ cations and chromate (CrO4) 2- anions only

Cr3+ and dichromate anions only

Cr2+, Cr3+ cations, and chromate (CrO4) 2- anions (correct)

Cr2+ and Cr3+ cations only

Which ion complex is present in the 'green' solutions of chromium (III)?

[Cr(H2O)4OH]3-

[Cr(H2O)5CI]2+ (correct)

[Cr(H2O)4C12] +

[Cr(H2O)6]

Why are Cr2+ ions rarely encountered in inorganic qualitative analysis?

They decompose even in water slowly with hydrogen formation Signup and view all the answers

What is the color of the solutions where the hexaquochromate (III) ion is present?

Violet Signup and view all the answers

How does dilute sulfuric acid react with chromium?

Attacks chromium slowly with the formation of hydrogen gas Signup and view all the answers

What happens when aluminum objects are exposed to air?

They form a protective oxide layer on the surface. Signup and view all the answers

How does concentrated HCl react with aluminum?

Dissolves aluminum with the evolution of hydrogen gas. Signup and view all the answers

What is the valence of chromium in chromic compounds?

+3 Signup and view all the answers

Which statement about aluminum sulfide is correct?

It forms in attractive crystal shapes. Signup and view all the answers

What is the effect of adding some mercury (II) chloride to the mixture of aluminum and acid?

Speeds up the dissolution process. Signup and view all the answers

Which compound is formed when Manganese reacts with warm water?

Mn(OH)2 Signup and view all the answers

What happens when hot, concentrated H2SO4 attacks Manganese?

Sulfur dioxide is evolved Signup and view all the answers

Which characteristic describes chromium (Cr3+)?

Seldom seen in the free state. Signup and view all the answers

Which color do the Mn(II) salts appear to be in solutions?

Pink Signup and view all the answers

What type of ions does aluminum form with alkali hydroxides?

[Al(OH)4] - ions Signup and view all the answers

How many oxides of manganese are known?

Six Signup and view all the answers

What do Mn(II) cations derive from?

Manganese oxide (MnO) Signup and view all the answers

Which statement about manganese compounds is correct?

Mn(VII) compounds contain the permanganate ion (MnO4-) Signup and view all the answers

What is the correct statement about zinc's physical properties?

Zinc melts at 410°C and boils at 906°C Signup and view all the answers

Which statement about zinc's reactivity with acids is incorrect?

Zinc dissolves in very dilute HNO3 without gas evolution Signup and view all the answers

What happens when zinc reacts with hot, concentrated H2SO4?

Sulfur dioxide gas is evolved Signup and view all the answers

Which statement about zinc's reaction with alkalis is correct?

Zinc dissolves in alkali hydroxides, forming tetrahydroxozincate(II), [Zn(H2O)4]2- Signup and view all the answers

What are the applications of metallic zinc mentioned in the text?

Making brass and galvanizing iron Signup and view all the answers

Study Notes

Chromium and Its Behavior

Chromium reacts with atmospheric oxygen, forming a protective oxide layer which inhibits further oxidation.
In aqueous solutions, chromium forms Cr³⁺ and Cr²⁺ ions, with Cr³⁺ being more stable.
The 'green' solutions of chromium (III) contain the hexaquochromate (III) ion, [Cr(H₂O)₆]³⁺.
Cr²⁺ ions are rarely observed in inorganic qualitative analysis due to their instability and tendency to oxidize to Cr³⁺.

Chromium Solutions and Reactions

Hexaquochromate (III) solutions exhibit a green color.
When treated with dilute sulfuric acid, chromium can be oxidized to higher oxidation states.

Aluminum and Its Reactions

When exposed to air, aluminum forms a protective oxide layer that prevents further corrosion.
Concentrated HCl reacts with aluminum, generating hydrogen gas and forming aluminum chloride.
The valence of chromium in chromic compounds is +3.

Aluminum Compounds and Reactions

Aluminum sulfide (Al₂S₃) is known to release hydrogen sulfide gas upon reaction with moisture.
Adding mercury (II) chloride to a mixture of aluminum and acid leads to the formation of elemental mercury and aluminum chloride.

Manganese and Its Compounds

When manganese reacts with warm water, manganese(II) hydroxide is formed.
Hot, concentrated H₂SO₄ reacts with manganese, leading to the formation of manganese sulfate and release of sulfur dioxide.
Characteristics of Cr³⁺ include being a hydrated ion that imparts a distinct color to solutions.
Mn(II) salts appear pale pink in solutions.

Aluminum and Manganese Reactions

Aluminum forms aluminate ions with alkali hydroxides.
There are seven known oxides of manganese, including MnO and MnO₂.
Mn(II) cations derive from oxidation states of manganese when reacting with acids.

Miscellaneous Compounds and Zinc Properties

Manganese compounds exhibit various oxidation states and reactivity patterns.
Zinc has a low melting point and high electrical conductivity.
An incorrect statement about zinc's reactivity with acids is often misconstrued; zinc reacts effectively with dilute acids but less so with concentrated ones.
When zinc reacts with hot, concentrated H₂SO₄, hydrogen gas is released, and zinc sulfate forms.
Zinc reacts with alkalis to form zincates, exhibiting amphoteric behavior.

Applications of Zinc

Zinc is utilized in galvanization, making alloys, and as a dietary supplement due to its essential role in human health.

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Test your knowledge on the properties of aluminum including its color, melting point, reaction with acids, and oxide layer formation when exposed to air.