REACTION OF METALS WITH OXYGEN/AIR

The following experiments show the reaction of metals with Oxygen and air.

Burning Magnesium

Procedure

(a) Cut a 2cm length piece of magnesium ribbon. Using a pair of tongs introduce it to a Bunsen flame. Remove it when it catches fire. Observe.

Place the products in a beaker containing about 5cm₃ of water.

Test the solution/mixture using litmus papers

(b)Cut another 2cm length piece of magnesium ribbon. Using a pair of tongs introduce it to a Bunsen flame. When it catches fire, lower it slowly into a gas jar containing Oxygen. Place about 5cm3 of water into the gas jar.

Test the solution/mixture using litmus papers. Test the solution/mixture using litmus papers

Observations

(a) In air

Magnesium burns with a bright blindening flame in air forming white solid/ash /powder. Effervescence/bubbles/ fizzing Pungent smell of urine.

Blue litmus paper remains blue. Red litmus paper turns blue

(b) In pure Oxygen

Magnesium burns faster with a very bright blindening flame pure oxygen forming white solid/ash /powder.

No effervescence/bubbles/ fizzing.

No pungent smell of urine. Blue litmus paper remains blue. Red litmus paper turns blue

Explanation

Magnesium burns in air producing enough heat energy to react with both Oxygen and Nitrogen to form Magnesium Oxide and Magnesium nitride.

Both Magnesium Oxide and Magnesium nitride are white solid/ash /powder.

Chemical equations

Magnesium + Oxygen ->Magnesium Oxide

2Mg(s) + O₂(g) -> 2MgO(s)

Magnesium + Nitrogen ->Magnesium Nitride

3Mg(s) + N₂(g) ->Mg3N₂ (s) Magnesium Oxide dissolves in water to form a basic/alkaline solution of Magnesium hydroxide Chemical equations

MagnesiumOxide + Water ->Magnesium hydroxide

2Mg(s) + O₂(l) -> 2MgO(s)

Magnesium Nitride dissolves in water to form a basic/alkaline solution of Magnesium hydroxide and producing Ammonia gas. Ammonia is also an alkaline/basic gas that has a pungent smell of urine.

Chemical equations

Magnesium Nitride + Water ->Magnesium hydroxide + Ammonia gas

Mg3N₂ (s)+ 6H₂O (l) -> 3Mg(OH)₂(aq) + 2NH₃(g)

1. Burning Sodium

Procedure

(a) Carefully cut a very small piece of sodium. Using a deflagrating spoon introduce it to a Bunsen flame. Remove it when it catches fire. Observe.

Place the products in a beaker containing about 20cm₃ of water. Test the solution/mixture using litmus papers

(b) Carefully cut another very small piece of sodium. Using a deflagrating spoon introduce it to a Bunsen flame. When it catches fire, lower it slowly into a gas jar containing Oxygen. Place about 20 cm₃ of water into the gas jar. Test the solution/mixture using litmus papers. Test the solution/mixture using litmus papers

Observations

(a) In air

Sodium burns with a yellow flame in air forming a black solid. Blue litmus paper remains blue. Red litmus paper turns blue

(b) In pure Oxygen

Sodium burns faster with a golden yellow flame in pure oxygen forming a yellow solid. Effervescence/bubbles/ fizzing.

Gas produced relights glowing splint.

Blue litmus paper remains blue. Red litmus paper turns blue.

Explanation

(a)Sodium burn in air forming black Sodium Oxide

Chemical equations

Sodium + Oxygen/air -> Sodium Oxide

4Na(s) + O₂(g) -> 2Na₂O(s)

Sodium Oxide dissolves in water to form a basic/alkaline solution of Sodium hydroxide

Chemical equations

Sodium Oxide + Water ->Sodium hydroxide

Na₂O(s) + H₂O (l) -> 2NaOH(aq)

(b)Sodium burns in pure oxygen forming yellow Sodium peroxide

Chemical equations

Sodium + Oxygen -> Sodium peroxide 2Na(s) + O₂(g) -> Na₂O₂ (s) Sodium peroxide dissolves in water to form a basic/alkaline solution of Sodium hydroxide. Oxygen is produced.

Chemical equations

Sodium Oxide + Water -> Sodiumhydroxide + Oxygen 2Na₂O₂ (s) + 2H₂O (l) -> 4NaOH(aq) + O₂ (l)

Burning Calcium

Procedure

(a)Using a pair of tongs hold the piece of calcium on a Bunsen flame. Observe.

Place the products in a beaker containing about 2cm3 of water. Test the solution/mixture using litmus papers

(b)Using a pair of tongs hold another piece of calcium on a Bunsen flame. Quickly lower it into a gas jar containing Oxygen gas .Observe.

Place about 2cm₃ of water.Swirl.

Test the solution/mixture using litmus papers

Observations

(a)In air

Calcium burns with difficulty producing a faint red flame in air forming a white solid. Blue litmus paper remains blue. Red litmus paper turns blue

(b) In pure Oxygen

Calcium burns with difficulty producing a less faint red flame Oxygen forming a white solid.

Blue litmus paper remains blue. Red litmus paper turns blue

Explanation

(a)Calcium burns in air forming white calcium Oxide. Calcium Oxide coat/cover the calcium preventing further burning.

Chemical equations

Calcium + Oxygen/air -> calcium Oxide

2Ca(s) + O₂(g) -> 2CaO(s)

Small amount of Calcium Oxide dissolves in water to form a basic/alkaline solution of Calcium hydroxide. The common name of Calcium hydroxide is lime water.

Chemical equations

Calcium Oxide + Water ->Calcium hydroxide

CaO(s) + H₂O (l) -> Ca(OH)₂ (aq)

1. Burning Iron Procedure

(a)Using a pair of tongs hold the piece of Iron wool/steel wire on a Bunsen flame.

Observe.

Place the products in a beaker containing about 2cm3 of water. Test the solution/mixture using litmus papers (b)Using a pair of tongs hold another piece of Iron wool/steel wire on a Bunsen flame. Quickly lower it into a gas jar containing Oxygen gas .

Observe.

Place about 2cm₃ of water. Swirl. Test the solution/mixture using litmus papers

Observations

(a) In air

Iron wool/steel wire burns producing a Orange flame in air forming a brown solid.

Blue litmus paper remains blue. Red litmus paper turns faint blue

(b) In pure Oxygen

Iron wool/steel wire burns producing a golden Orange flame in Oxygen forming a Brown solid. Blue litmus paper remains blue. Red litmus paper turns faint blue

Explanation

(a)Iron burns in air forming brown Iron(III) Oxide

Chemical equations

Iron + Oxygen/air -> Iron(III)Oxide 4Fe(s) + 3O₂(g) -> 2Fe₂O₃(s)

Very small amount of Iron(III)Oxide dissolves in water to form a weakly basic/alkaline brown solution of Iron(III) hydroxide.

Chemical equations

Calcium Oxide + Water ->Iron(III)hydroxide Fe₂O₃(s) + 3H₂O (l) ->2Fe(OH)₃ (s)

1. Burning Copper

Procedure

(a)Using a pair of tongs hold the piece of copper turnings/shavings on a Bunsen flame. Observe.

Place the products in a beaker containing about 2cm₃ of water. Test the solution/mixture using litmus papers

(b)Using a pair of tongs hold another piece of Copper turnings/shavings on a Bunsen flame. Quickly lower it into a gas jar containing Oxygen gas .

Observe.

Place about 2cm₃ of water. Swirl. Test the solution/mixture using litmus papers

Observations

(a) In air

Copper turnings/shavings burns with difficulty producing a green flame in air forming a black solid.

Blue litmus paper remains blue. Red litmus paper turns faint blue

(b) In pure Oxygen

Copper turnings/shavings burns less difficulty producing a green flame in Oxygen forming a Brown solid.

Blue litmus paper remains blue. Red litmus paper turns faint blue

Explanation

(a)Copper burns in air forming black Copper(II) Oxide

Chemical equations

Copper + Oxygen/air -> Copper(II)Oxide

2 Cu(s) + O2(g) -> 2CuO(s)

Very small amount of Copper(II)Oxide dissolves in water to form a weakly basic/alkaline blue solution of Copper(II) hydroxide.

Chemical equations

Copper(II) Oxide + Water -> Copper(II)hydroxide

CuO(s) + H₂O (l) ->Cu(OH) ₂ (s)