Mr of a hydrated sodium carbonate

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In summary, a sample of a hydrate of sodium carbonate was dissolved in water and titrated with hydrochloric acid. The number of moles of Na2CO3 was determined to be 0.0243 in the original 3.01g sample, making the original formula Na2CO3.H2O. The molar mass of this compound is 124g/mol.
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nobahar
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Homework Statement


Sodium Carbonate forms a number of hydrates of general formula Na2CO3.xH2O.
A 3.01g sample of one of these hydrates was dissolved in water and the solution was made up to 250cm3. In a titration, 25cm3 portion of this solution required 24.3cm3 of 0.2 mol dm-3 hydrochloric acid for complete reaction.


Homework Equations



Na2CO3 + 2HCl is the important bit

The Attempt at a Solution


I got the number of moles of HCl to be 4.86 x 10-3 mol; therefore the number of moles of Na2CO3 to be 2.43 x 10-3 mol in 25cm3 and so 0.0243 mol in the orginal 250cm3.
This must be the number of moles of Na2CO3 in the original 3.01g. 0.0243 moles of Na2CO3 weighs 2.5758g, and so the water must make up 0.4342g (derived from 3.01g - 2.5758g). The number of moles of H2O is therefore 0.024. I figured that the number of moles of Na2CO3 to H2O is approximately 1, and so the orginal formula must be Na2CO3.H2O (i.e. x is 1).
The Mr is therefore106+(1 x 18) = 124g/mol.
Is this correct?
Thanks in advance.
 
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  • #2
I fear may question may appear too long. This is the important part:

This must be the number of moles of Na2CO3 in the original 3.01g. 0.0243 moles of Na2CO3 weighs 2.5758g, and so the water must make up 0.4342g (derived from 3.01g - 2.5758g). The number of moles of H2O is therefore 0.024. I figured that the number of moles of Na2CO3 to H2O is approximately 1, and so the orginal formula must be Na2CO3.H2O (i.e. x is 1).
The Mr is therefore106+(1 x 18) = 124g/mol.


Thanks in advance.
 
  • #3
Looks OK to me.

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  • #4
Thanks Borek.
 

1. What is the Mr of a hydrated sodium carbonate?

The Mr of a hydrated sodium carbonate is a measure of its molecular weight, and is calculated by adding the atomic weights of all the atoms in its chemical formula. For hydrated sodium carbonate, the Mr would be calculated as follows: Na2CO3 + (H2O x n) where n is the number of water molecules in the compound.

2. How is the Mr of a hydrated sodium carbonate determined?

The Mr of a hydrated sodium carbonate can be determined through various methods, such as mass spectrometry or by using a chemical formula and the periodic table to calculate it. In some cases, it may also be listed on the compound's safety data sheet or on its packaging.

3. Why is it important to know the Mr of a hydrated sodium carbonate?

Knowing the Mr of a hydrated sodium carbonate is important for many reasons, including determining its chemical properties, predicting its behavior in reactions, and ensuring accurate measurements and calculations in experiments and industrial processes.

4. Does the Mr of a hydrated sodium carbonate change in different conditions?

The Mr of a hydrated sodium carbonate will not change in different conditions, as it is a constant value based on the chemical composition of the compound. However, the physical properties of the compound may change in different conditions, such as temperature or pressure.

5. How does the Mr of a hydrated sodium carbonate compare to other compounds?

The Mr of a hydrated sodium carbonate may be higher or lower than other compounds, depending on their chemical formulas and molecular weights. It is important to compare the Mr of compounds in order to understand their relative sizes and properties.

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