Sunday, October 11, 2009

Question for this week (Mole)

The formula of hydrated sodium carbonate crystals Na2CO3.xH2O.
In the experiment, 0.57 g sample of these crystals dissolved in 25.0 cm3 of distilled water and subsequently titrated with dilute hydrochloric acid. 19.95 cm3 of 0.20 mol/dm3 of dilute hydrochloric acid was required for the titration.

(a) Calculate the number of moles of Na2CO3.xH2O which reacted with the dilute hydrochloric acid.
Answer: 0.001995 moles

(b) Find x and determine the formula of hydrated sodium carbonate.
Answer: 10






[credits: Understanding 'O' level chemistry through problem solving]

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