chem lab report 10

CHEMISTRY LAB REPORTPRACTICAL 10

INTRODUCTION

The s-block of the periodic table contains the most reactive and in chemical terms, the most typically metallic elements. All the elements in group I are highly reactive, but those in group II are slightly less. In this practical you will study some of the properties of the group I elements and their compounds. We will concentrate on the three elements lithium, sodium and potassium.

DATA COLLECTION

Experiment 1: Reactivity with water.

Element Observation pH indicator

Lithium Move slowly on the surface of the water. Emitted a negligible amount of white smoke The reaction produced a colourless solution.

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Sodium

Move moderately on the surface of the water with ‘hiss’ sound.

It burnt with yellow in colour. Emitted white smoke The reaction produced colourless solution

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Potassium

Move enthusiastically on the surface of the water with ‘hiss’ and ‘pop’ sound

It burnt with red in colour in colour. Emitted large amount of white smoke. The reaction produced colourless solution.

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Experiment 2: Reactivity with chlorine.

Alkali Metal Observation

Lithium Burnt slowly with the red flame Very heavy black soot are produced A white solid is produced

Sodium Moderate time to burn out with the yellow flame Heavy black soot are produced A white solid is produced

Potassium Take short time to burn out with purple flame White and black soot are produced A white solid is produced

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Experiment 3: Reactivity with oxygen

Element Observation pH indicator

Lithium

Burn slowly with the red flame Emitted white smoke and the element

changed its colour from grey to white in colour eventually.

When the white solid is mixed up with water, it’s produced colourless solution.

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Sodium

Burnt moderately with the yellow flame. Emitted small amount of white smoke

and the element changed its colour from white to black in colour.


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Potassium

Burnt robustly until the element become slightly red flame in colour

Emitted big amount of white smoke and the element changed from white to black colour


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Experiment 4: Flame tests

Metal chloride + HCl

Observation

Lithium Chloride (LiCl)

Change the mix solution to green-yellowish Produced red flame

Sodium Chloride (NaCl)

Change the mix solution to yellowish Produced violet flame

Potassium Chloride (KCl)

Change the mix solution to green-yellowish Produced yellow flame

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DATA PROCESSING

Experiment 1: Reactivity with water

Alkali metals react with water to produce alkali solution and release hydrogen gas to the surroundings.

The chemical equations for this experiment are:

2Li(s) + 2H2O(aq) 2LiOH(aq) + H2(g)

2Na(s) + 2H2O(aq) 2NaOH(aq) + H2(g)

2K(s) + 2H2O(aq) 2KOH(aq) + H2(g)

As the reaction happened down the alkali metal group, the reactivity also increases. LiOH, NaOH, and KOH when tested with ph indicator, the pH result obtained were above 7. Therefore it shows alkali characteristic.

Experiment 2: Reactivity with chlorine


2Li(s) + Cl2(g) 2LiCl(s)

2Na(s) + Cl2(g) 2NaCl(s)

2K(s) + Cl2(g) 2KCl(s)

Lithium, Sodium, and Potassium reacted with chlorine gas producing metal chloride. Scientifically in this experiment, the above reaction happened when the alkali metal donor one electron which is located in the outer most orbital to the chlorine atom so that they will achieve the inert noble gas configuration.

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Experiment 3: Reactivity with oxygen


4Li(s) + O2(g) 2Li2O(s)

4Na(s) + O2(g) 2Na2O(s)

4K(s) + O2(g) 2K2O(s)

Lithium, Sodium, and Potassium react with oxygen to produce metal oxide which is white in colour. According to the observation from the reaction of alkali metal between the oxygen, it can deduce that the reactivity increases as going down the alkali metal group.

The metal oxide obtained can be dissolve in water producing metal hydroxide solution. The solutions gave the reading of alkali when tested with pH indicator which is above 7.

The chemical equation;

Li2O(s) + H2O 2LiOH(aq)

Na2O(s) + H2O 2NaOH(aq)

K2O(s) + H2O 2KOH(aq)

Experiment 4: Flame test

The alkali metal gave the different colour of flame as below;

Lithium – redSodium – YellowPotassium – Blue

Scientifically when the alkali metals are placed in a flame, they give out attribute colours. This happened because the alkali metals ions are reduced to the gaseous metal atoms state. The atoms gained enough energy by the high temperature so that the electron in the valence electron shell can excite to the high energy level. In order to return to its ground state, the electron must lose the energy. So they emitted the energy in the form of visible light. The alkali metals gave out different colours due to the emission at certain wavelength. The wavelength is considered by the exciting state valence electron when its drop from the high energy level subshell to lower energy subshell.

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chem lab report 10

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