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# titration watch

1. Sodium carbonate exists in hydrated form, Na2CO3.xH2O, in the solid state. 3.5 g of a sodium carbonate sample was dissolved in water and the volume made up to 250 cm3. 25.0 cm3 of this solution was titrated against 0.1 moldm-3 HCl and 24.5 cm3 of the acid were required. Calculate the value of x given the equation:

Na2CO3 + 2HCl à 2NaCl + CO2 + H2O
2. (Original post by sat1011)
Sodium carbonate exists in hydrated form, Na2CO3.xH2O, in the solid state. 3.5 g of a sodium carbonate sample was dissolved in water and the volume made up to 250 cm3. 25.0 cm3 of this solution was titrated against 0.1 moldm-3 HCl and 24.5 cm3 of the acid were required. Calculate the value of x given the equation:

Na2CO3 + 2HCl à 2NaCl + CO2 + H2O
find moles of HCl using concentration and volume given
divide this by 2 to find moles in Na2CO3
multiply this by 10 to find moles in original solution
use number of moles and mass (3.5g) to find relative formula mass of hydrated sodium carbonate
take away relative formula mass of Na2CO3 only
divide this by 18 and round if necessary to give x

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