Determine the concentration of a limewater solution.

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Name: Aisha Trew

Candidate Number: 6535

Centre Name: Bullers Wood school

Centre Number: 14217

 

To determine the concentration of a limewater solution

Aim: To do an acid based titration to find out the concentration of limewater

Introduction

In this experiment, an acid-alkali titration will be done between calcium hydroxide and hydrochloric acid to find out the exact concentration of calcium hydroxide.

Acid + alkali → salt + water

Hydrochloric acid + calcium hydroxide → calcium chloride + water

Symbol equation     2HCl(aq) + Ca(OH)2(aq)→ CaCl2(aq) + 2H2O(l)

I’ll be using phenolphthalein indicator because it is good with strong acid and alkalis, it will be added to the hydrochloric acid which will turn the solution pink/red, when the solution is neutralise, therefore the end of the titration the solution will then turn clear.

The concentration of the hydrochloric acid given is 2.00 mol dm-3 which is too concentrated to titrate the calcium hydroxide.

To find the concentration needed to neutralise the calcium hydroxide which concentration is approximately 1 g dm-3.

 

G dm-3= mol dm-3 x mr

Therefore mol dm-3 = g dm-3/ Mr 

= 1 / (40.1 + 2+ 32)

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= 1/ 74.1

= 0.013495276 mol dm-3

 As I predict that, I will use 25.0 cm3 of calcium hydroxide per titration

Moles = concentration x volume

= 0.01 x (25.0 /1000)

=0.0003 moles (1 s.f)

As the equation is 2HCl + Ca(OH)2→ CaCl2 + 2H2O

The ratio of Hydrochloric acid to Calcium hydroxide is 2:1

Therefore the moles of hydrochloric acid is 0.0003 x 2 = 0.0006 moles

Volume HCl is needed is approximately 30.0cm per titration

Concentration= moles / volume

=0.0006/ (30.0/1000)

=0.02 mol dm-3

As the concentration of hydrochloric acid given is 2.00 mol dm-3 and ...

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