Determining the Relative Atomic Mass of Lithium

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Determining the Relative Atomic Mass of Lithium

Introduction

My aim of this experiment will be to determine the R.A.M using two separate methods

In the first method I will dissolve a piece of lithium of a known mass in water, I will then collect the hydrogen gas produced, which can be used to calculate the relative atomic mass of Lithium.

The balanced equation of our reaction is shown below;

2Li + 2H2O 2LiOH + H2

In the second method I will do a titration experiment of lithium hydroxide (produced in experiment 1)

The balanced equation of our reaction in experiment 2 is shown below;

LiOH + HCl LiCl + H20

Background Information

Lithium is an alkali metal in group 1 of the periodic table. It is a metallic element and does not decompose however it is highly in contact with many other substances. It can react violently with water, the humidity in air, and the moisture in other substances releasing hydrogen gas.

Apparatus

* Lithium (0.08g)

* Pan Balance

* Conical Flask

* Bowl

* Measuring Cylinder (250cm3)

* Delivery tube and Bung

* Goggles

* Filter

* Clamp

Method

I set up the apparatus as shown above. I placed water into the bowl (I used a big bowl because the measuring cylinder was 250cm3 which was too big to fit into a beaker). I made sure there was no air in the measuring cylinder and that it only contains water and I put it into the bowl of water over the delivery tube, I then got a clamp stand to hold the measuring cylinder.

The lithium was taken and the oil was removed off it using the filter. The lithium was then placed in a pan balance once removing as much oil as possible. The measured mass of lithium was placed in a conical flask and the bung put in place to collect the H2 produced and so that no gas came out of the top. Once the reaction is finished I took the reading from the measuring cylinder of the volume of hydrogen produced.

Method 1 Results

mass

Volume of H2 produced

0.10g

76cm3

Apparatus

§ clamp

§ Beaker

§ Phenolethein Indicator

§ Pippete

§ LiOH (from experiment 1)

§ HCl

§ Goggles

§ Measuring Cylinder(250cm3)

Risk assesment

Ø Lithium is a flammable solid, it reacts violently with water to give

flammable hydrogen gas. Lithium is corrosive to eyes (may cause

bindness), skin, nose, throat and stomach.(if it gets onto the skin or

eyes then immediately flush with water)

Ø Lithium hydroxide can cause severe irritation and corrosive tissue

damage. Concentrated concentrations of lithium hydroxide may rapidly
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cause deep burns if there is skin contactt

Ø HCl is corrosive, may cause severe burns to all body tissue. May be

fatal if swallowed or inhaled

Method

I got 25cm3 of lithium hydroxide solution and put it into a clean

250cm3 conical flask. I filled the burette with HCl making sure that

the tap is closed. I then rinsed out the burette by opening the tap

and allowing the HCl to run, this will release any air bubbles and

will also ...

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