Aim: To determine the water of crystallization in washing soda crystals (Na2CO3.xH2O) Research Question: What is the percentage composition and the amount (in moles) of water in the given ionic hydrate? (Na2CO3.xH2O) Background Information:
Sodium Carbonate also known as Washing Soda (Na2CO3.xH2O) is a sodium salt of carbonic acid. Sodium carbonate is domestically well known for its everyday use as a water softener. It is also used to remove grease, oil and wine stains. It can be extracted from the ashes of many plants. It is synthetically produced in large quantities from salt (sodium chloride) and limestone in a process known as the Solvay process.
Titration is also known as titrimetry. It is the process, operation, or method of determining the concentration of a substance in a solution by adding a standard reagent of known concentration to it, in carefully measured amounts until a reaction of definite and known proportion is completed, as shown by a colour change or by electrical measurement, and then calculating the unknown concentration. There are many types of titration, like acid is the type of titration used in this experiment. -base titration, redox titration, gas phase titration etc. Acid-base titration When water is chemically combined with other elements in a crystal, it is known as water of crystallization. The water of crystallization is necessary for the maintenance of crystalline properties, but it can be removed by heat. Water of crystallization is also known as water of hydration or crystallization water and it is mostly found in a definite (stoichiometric) ratio. Hydrated ionic compounds are regular ionic compounds that contain a specific number of water molecules in their respective crystals. Hydrates that spontaneously lose water to the atmosphere are known as efflorescent. Compounds that spontaneously absorb water from the atmosphere are known as hygroscopic. Each ionic hydrate has a fixed water of crystallization, and this varies for each compound. For example: CuSO4 has a water of crystallization of 5 water molecules, whereas FeSO4 has 7 water molecules.
Hydrochloric acid (HCl) is a clear, colourless solution of aqueous hydrogen chloride. It is a highly corrosive, strong mineral acid with many industrial uses. Hydrochloric acid is found naturally in gastric acid. Hydrochloric acid is the preferred acid in titration for determining the amount of bases. It is also used as a household cleaning product, for leather processing and also for food production.
Methyl orange is frequently used in titration. It is of a reddish yellow colour. It is an acid indicator. Unlike a universal indicator, methyl orange does not have a full spectrum of colour change, but has a sharper end point. Hence it will change to a reddish colour when in the presence of an acid and into a yellow colour when in the presence of an alkali.
There are two parts to this particular experiment. One is while using anhydrous sodium carbonate solution, and the other using washing soda crystals. In the first part, I predict that when a few drops of the methyl orange indicator is added to 10cm3 of 0.1M anhydrous sodium carbonate solution, and then titrated with HCl and recorded, the amount of HCl used would stay almost constant throughout all the 3 trials.
In the 2nd part of the experiment, where washing soda crystals are used, I predict that after the washing soda crystals are weighed and recorded and then dissolved and diluted with distilled water, and after a few drops of the methyl orange indicator is added to this solution, and then titrated with HCl and then recorded, I predict that the amount of HCl used will remain almost constant throughout all the 3 trials in the experiment.
If the experiment is carried out with minimal errors the water of crystallization obtained will be very close to the literature value. Literature Value:
The literature value for the amount of water molecules in the hydrated salt...
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