Unit 3.5.5 - Reactions in Inorganic Compounds in Aqueous Solution Flashcards by Hollie Pilkington

What colour is [Cr(OH)₆]³⁻

Green solution

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What is chelation?

When unidentate ligands are exchanged for bidentate or multidentate ligands.

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Using the ∆G = ∆H - T∆S why is chelation always feasible?

∆H is very small and ∆S is very large and positive meaning ∆G is large and negative.

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What is a Lewis acid?

Electron pair acceptor

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What is the equation for the reaction between copper aqua ions and excess ammonia?

[Cu(H₂O)₆]²⁺(aq) + 4NH₃(aq) → [Cu(NH₃)₄(H₂O)₂]²⁺(aq) + 4H₂O(l)

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What colour is Cu(H₂O)₄(OH)₂

Blue precipitate

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What is the equation when ammonia is added to a metal aqua 3+ complex?

[M(H₂O)₆]³⁺(aq) + 3NH₃(aq) ⇋ [M(H₂O)₃(OH)₃(s) + 3NH₄⁺(aq)

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What colour is [Cr(NH₃)₆]³⁺

Purple solution

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What is a Lewis base?

Electron pair donor

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In general how many water molecules form co-ordinate bonds with each metal ion?

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Name two transition metals that are amphoteric?

Al³⁺ and Cr³⁺

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What colour is [Co(NH₃)₆]²⁺

Straw coloured solution

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Why don’t metal 3+ ions react with carbonates the same as metal 2+ ions?

Metal 3+ ions form more acidic solutions so are stronger acids.

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When H₂O ligands are swapped for NH₃ ligands why doesn’t the co-ordination number or shape change?

Because the ligands are similar size and uncharged.

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During ligand exchange, if the ligands are different sizes does the co-ordination and shape change?

Yes

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What is the equation for the reaction between cobalt aqua ions and excess ammonia?

[Co(H₂O)₆]²⁺(aq) + 6NH₃(aq) → [Co(NH₃)₆]²⁺(aq) + 6H₂O(l)

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What is the equation for the reaction between chromium aqua complex and EDTA⁴⁻?

[Cr(H₂O)₆]²⁺ + EDTA⁴⁻ → [Cr(EDTA)]²⁻ + 6H₂O

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What colour is [CuCl₄]²⁻?

Yellow green solution

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When is ligand exchanged not easily reversed?

When the new complex ion is more stable than the old one.

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What colour is [Cr(H₂O)₆]³⁺

Violet solution

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Co-ordinate bonds are formed between which sort of bases and acids?

Lewis

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What six metal aqua ions do you have to know about?

Fe²⁺, Cu²⁺, Co²⁺, Al³⁺, Cr³⁺ and Fe³⁺

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In excess ammonia which metal hydroxides undergo ligands substitution?

Co²⁺, Cu²⁺ and Cr³⁺

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Do metal aqua 2+ ions form weak or strong acidic solutions? And why?

Weak - there is only slight disassociation

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Why are some metal hydroxides amphoteric?

Because some can dissolve in excess base as well as excess acid.

What is the equation for the reaction between cobalt aqua ions and chloride ions?

[Co(H₂O)₆]²⁺(aq) + 4Cl⁻(aq) ⇋ [CoCl₄]²⁻(aq) + 6H₂O(l)

What is the equation for the reaction between copper aqua complexes and 1,2-diaminoethane?

[Cu(H₂O)₆]²⁺(aq) + 3NH₂CH₂CH₂NH₂(aq) → [Cu(NH₂CH₂CH₂NH₂)₃]²⁺(aq) + 6H₂O(l)

What colour is [Cu(NH₃)₄(H₂O)₂]²⁺

Deep Blue solution

Are reaction with a decrease or increase in entropy more likely to happen?

Increase

What happens when transitions metals dissolve in water?

The water molecules form co-ordinate bonds with the metal ions, forming a metal-aqua complex.

What colour is [Co(H₂O)₆]²⁺

Pink solution

Give an example of a Bronsted Lowry base that is also a Lewis base.

Water

What is the overall equation for when OH⁻ are added to metal aqua +2 complexes (to the end point) ?

[M(H₂O)₆]²⁺(aq) + 2H₂O(l) ⇋ [M(H₂O)₄(OH)₂](aq) + 2H₃O⁺(aq)

What colour is [Al(H₂o)₂(OH)₄]⁻

Colourless solution

What is a Bronsted Lowry base?

Proton acceptor

What is the equation for the reaction between copper aqua ions and chloride ions?

[Cu(H₂O)₆]²⁺(aq) + 4Cl⁻(aq) ⇋ [CuCl₄]²⁻(aq) + 6H₂O(l)

What colour is [Fe(H₂O)₄(OH)₂]

Green precipitate

How can you increase the amount of products formed in this reaction : [Co(H₂O)₆]²⁺(aq) + 4Cl⁻(aq) ⇋ [CoCl₄]²⁻(aq) + 6H₂O(l)?

Adding more HCl

What colour is [Fe(H₂O)₆]³⁺

Yellow solution

What colour is [CoCl₄]²⁻

Blue solution

What is the equation when a metal 3+ hydroxide is in excess H⁺?

[M(H₂O)₃(OH)₃](s) +3H⁺(aq) ⇋ [M(H₂O)₆]³⁺(aq)

Is enthalpy change for ligand exchange large or small? And why?

Small - a similar amount of energy is required to break the bonds in the products as it is to form the bonds in the reactants.

Which metal aqua complex undergo partial substitution of NH₃ ligands?

Cu²⁺

What is the Lewis Theory of acids and bases based on?

Electron transfer

What type of ligands are the most stable?

Multidentate

What is the equation when ammonia is added to a metal aqua 2+ complex?

[M(H₂O)₆]²⁺(aq) + 2NH₃(aq) ⇋ [M(H₂O)₄(OH)₂(s) + 2NH₄⁺(aq)

What colour is FeCO₃

Green precipitate

What colour is Cr(H₂O)₃(OH)₃

Green fucking precipitate

What colour is [Al(H₂O)₆]³⁺

Colourless solution

Do metal 2+ or metal 3+ ions form more acidic solutions?

Metal 3+ ions

What is the chelate effect?

When unidentate ligands are exchanged for multidentate ligands the complex is more stable because of the increase in entropy.

Why do water ligands act as a Lewis base?

Because they are donating a pair of electrons to the metal ion.

What is a Bronsted Lowry acid?

Proton donor

What is the total charge of a metal aqua complex?

The charge of the metal ion.

Other than adding OH⁻ ions how else can you form metal hydroxides from metal aqua complexes?

By mixing them with ammonia solution.

What is the equation when chromium hydroxide dissolves in excess base?

[Cr(H₂O)₃(OH)₃](s) + 3OH⁻(aq) ⇋ [Cr(OH)₆]³⁻(aq) + 3H₂O(l)

In what metal aqua complexes can water ligands be exchanged for chloride ligands?

Cu²⁺ and Co²⁺

What is ligand exchange?

Where one ligand is swapped for another.

What is the equation for when sodium hydroxide is added to [M(H₂O)₆]³⁺(aq)

[M(H₂O)₆]³⁺(aq) + 3OH⁻→[M(H₂O)₃(OH)₃](aq) + 3H₂O

In water what equilibrium equation do metal aqua +3 complexes form?

[M(H₂O)₆]³⁺(aq) + H₂O(l) ⇋ [M(H₂O)₅(OH)]²⁺(aq) + H₃O⁺(aq)

What is the equation for when metal 3+ ions react with sodium carbonate?

2[M(H₂O)₆]²⁺(aq) + 3CO₃²⁻(aq) ⇋ 2[M(H₂O)₄(OH)₂](s) + 3CO₂(g) + 3H₂O(l)

What colour is [Al(H₂O)₃(OH)₃]

White precipitate

What is a hydrolysis/acidity reaction?

The initial equilibrium set up between the metal aqua complex and the water.

When metal 3+ aqua ions react with carbonates what will you see?

Bubbles of carbon dioxide.

When do H₂O stop being substituted for OH⁻ in metal aqua complexes when OH⁻ ions are being added to the equilibrium?

When there is no charge and there is a precipitate.

What colour is CuCO₃

Green-blue precipitate

What colour is Fe(H₂O)₃(OH)₃

Brown precipitate

What colour is [Cu(H₂O)₆]²⁺

Blue solution

What is the equation for when metal 2+ ions react with sodium carbonate?

[M(H₂O)₆]²⁺(aq) + CO₃²⁻(aq) ⇋ MCO₃(s) + 6H₂O(l)

What colour is [Co(H₂O)₄(OH)₂

Blue green precipitate

What is the general metal-aqua complex equation for +3 metal ions?

[M(H₂O)₆]³⁺

Do metal hydroxides act as Bronsted Lowry bases or acids and why?

Base - they can accept H+ ions

When exchanging smaller ligands for larger is entropy change large or small? And why?

Large - the number of molecules is increasing.

What is the equation when a metal 2+ hydroxide is in excess H⁺?

[M(H₂O)₄(OH)₂](s) +2H⁺(aq) ⇋ [M(H₂O)₆]²⁺(aq)

Which metal aqua complexes will the H₂O ligand fully substitute for NH₃ ligands?

Co²⁺ and Cr³⁺

Do metal ions acts as a Lewis acid or base when in aqueous solution and why?

Lewis acid - they're accepting a pair of electrons from the water molecules.

What happens when you add OH⁻ to this equilibrium: [M(H₂O)₆]³⁺(aq) + H₂O(l) ⇋ [M(H₂O)₅(OH)]²⁺(aq) + H₃O⁺(aq) ?

The OH⁻ ions remove H₃O⁺ ions, decreasing the concentration of the products, shifting the equilibrium to the right and so producing more [M(H₂O)₅(OH)]²⁺

What is the equation when aluminium hydroxide dissolves in excess base?

[Al(H₂O)₃(OH)₃](s) + OH⁻(aq) ⇋ [Al(H₂O)₂(OH)₄]⁻(aq) + H₂O(l)

What does amphoteric mean?

When something acts both as a Bronsted Lowry acid and base.

What is the overall equation for when OH⁻ are added to metal aqua +3 complexes (to the end point) ?

[M(H₂O)₆]³⁺(aq) + 3H₂O(l) ⇋ [M(H₂O)₃(OH)₃](aq) + 3H₃O⁺(aq)

Why do metal 3+ ions form more acidic solutions than metal 2+ ions (describe in 4 steps)?

1. ) Metal 3+ ions have a higher charged density 2. ) This makes them more polarising so they attract more electrons from the oxygen atoms of the co-ordinated water molecules 3. ) Weakening the OH bond 4. ) It is more likely that hydrogen ions will be released making them more acidic

Why is water a Bronsted Lowry base and a Lewis base?

When it reacts with hydrogen to form a hydroxium ion, during this it both accepts a proton and is an electron pair donor.

What colour is [Fe(H₂O)₆]²⁺

Green solution

What is the general metal-aqua complex equation for +2 metal ions?

[M(H₂O)₆]²⁺

What colour is CoCO₃

Pink precipitate

What is the equation for the reaction between chromium aqua ions and excess ammonia?

[Cr(H₂O)₆]³⁺(aq) + 6NH₃(aq) → [Cr(NH₃)₆]³⁺(aq) + 6H₂O(l)

Unit 3.5.5 - Reactions in Inorganic Compounds in Aqueous Solution Flashcards

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