Define reducing agent

A reducing agent is a species that loses electrons and causes the reduction of another species. Group 2 metals act as reducing agents because they lose two electrons to form 2+ ions.

Slaked lime is the common name for calcium hydroxide , Ca(OH) 2 , used to neutralise acidic soils in agriculture by reacting with excess H + ions.

True or False? The reactivity of Group 2 elements increases going down the group.

True. Atomic radius increases and there is greater shielding down the group, so the nuclear attraction on outer electrons decreases and they are lost more easily.

True or False? Group 2 hydroxide solutions become more alkaline going down the group.

True. Solubility of Group 2 hydroxides increases down the group, so more OH - ions are released into solution, giving a higher pH.

What happens to the first and second ionisation energies of Group 2 elements going down the group?

Both the first and second ionisation energies decrease down the group, as increasing atomic radius and shielding reduce the nuclear attraction on the outer electrons.

Why is barium sulfate safe to use in a barium meal despite barium ions being toxic?

Barium sulfate is insoluble , so it is not absorbed into the bloodstream from the gut and cannot cause toxic effects.

M (s) + .......... → M(OH) 2 (s) + .......... (g)

M (s) + 2H 2 O (l) → M(OH) 2 (s) + H 2 (g) The metal is oxidised (0 to +2) and hydrogen is reduced (+1 to 0).

CaCO 3 (s) + 2H + (aq) → .......... + H 2 O (l) + CO 2 (g)

CaCO 3 (s) + 2H + (aq) → Ca 2+ (aq) + H 2 O (l) + CO 2 (g) Calcium carbonate acts as a base , neutralising excess acid in the soil.

Why do Group 2 sulfates become less soluble going down the group?

As the cation radius increases down the group, the lattice enthalpy of the sulfate salt decreases less than the hydration enthalpy, making dissolution less energetically favourable.

What is the role of calcium hydroxide in agriculture?

Calcium hydroxide ( slaked lime ) is added to acidic soil to neutralise excess H + ions and raise the pH to a level suitable for crop growth.

True or False? Group 2 sulfates become more soluble going down the group.

False. Group 2 sulfates become less soluble going down the group — calcium sulfate is sparingly soluble, and barium sulfate is insoluble.

True or False? Magnesium hydroxide is highly soluble in water.

False. Magnesium hydroxide has very low solubility, giving a weakly alkaline solution of only pH ≈ 10, which is why it is safe to use as an antacid.

A LevelChemistryOCRFlashcards3. Periodic Table & EnergyGroup 2

Group 2 (OCR A Level Chemistry A): Flashcards

Exam code: H432

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Define reducing agent

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Define reducing agent
A reducing agent is a species that loses electrons and causes the reduction of another species. Group 2 metals act as reducing agents because they lose two electrons to form 2+ ions.
Define slaked lime
Slaked lime is the common name for calcium hydroxide, Ca(OH)₂, used to neutralise acidic soils in agriculture by reacting with excess H⁺ ions.
True or False?
The reactivity of Group 2 elements increases going down the group.
True.
Atomic radius increases and there is greater shielding down the group, so the nuclear attraction on outer electrons decreases and they are lost more easily.
True or False?
Group 2 hydroxide solutions become more alkaline going down the group.
True.
Solubility of Group 2 hydroxides increases down the group, so more OH^- ions are released into solution, giving a higher pH.
What happens to the first and second ionisation energies of Group 2 elements going down the group?
Both the first and second ionisation energies decrease down the group, as increasing atomic radius and shielding reduce the nuclear attraction on the outer electrons.
Why is barium sulfate safe to use in a barium meal despite barium ions being toxic?
Barium sulfate is insoluble, so it is not absorbed into the bloodstream from the gut and cannot cause toxic effects.
M (s) + .......... → M(OH)₂ (s) + .......... (g)
M (s) + 2H₂O (l) → M(OH)₂ (s) + H₂ (g)
The metal is oxidised (0 to +2) and hydrogen is reduced (+1 to 0).
CaCO₃ (s) + 2H⁺ (aq) → .......... + H₂O (l) + CO₂ (g)
CaCO₃ (s) + 2H⁺ (aq) → Ca²⁺ (aq) + H₂O (l) + CO₂ (g)
Calcium carbonate acts as a base, neutralising excess acid in the soil.
Why do Group 2 sulfates become less soluble going down the group?
As the cation radius increases down the group, the lattice enthalpy of the sulfate salt decreases less than the hydration enthalpy, making dissolution less energetically favourable.
What is the role of calcium hydroxide in agriculture?
Calcium hydroxide (slaked lime) is added to acidic soil to neutralise excess H⁺ ions and raise the pH to a level suitable for crop growth.
True or False?
Group 2 sulfates become more soluble going down the group.
False.
Group 2 sulfates become less soluble going down the group — calcium sulfate is sparingly soluble, and barium sulfate is insoluble.
True or False?
Magnesium hydroxide is highly soluble in water.
False.
Magnesium hydroxide has very low solubility, giving a weakly alkaline solution of only pH ≈ 10, which is why it is safe to use as an antacid.

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