Final answer:
To determine the formula of the hydrated sodium carbonate, we calculate the mass of water lost, determine the moles of anhydrous sodium carbonate and water, and establish the mole ratio to find the number of water molecules per formula unit of sodium carbonate. The formula of the hydrate is Na2CO3·nH2O, where 'n' represents this number.
Step-by-step explanation:
To determine the formula of the hydrate of sodium carbonate, we need to find out the number of moles of water lost upon heating. We start by calculating the mass of water lost by subtracting the mass of anhydrous sodium carbonate from the mass of the hydrated compound. From the student's data, 4.31 g of hydrated sodium carbonate results in 3.22 g of anhydrous sodium carbonate upon heating, which means: Mass of water lost = 4.31 g (hydrated compound) - 3.22 g (anhydrous compound) = 1.09 g of water
Next, we determine the number of moles of anhydrous sodium carbonate and water. The molar mass of Na2CO3 is (2 x 22.990) + (1 x 12.011) + (3 x 15.999) = 105.988 g/mol. The molar mass of water (H2O) is 18.015 g/mol.
Moles of Na2CO3 = 3.22 g / 105.988 g/mol
Moles of H2O = 1.09 g / 18.015 g/mol
Now we can find the mole ratio of Na2CO3 to H2O to determine the number of moles of water per mole of sodium carbonate in the hydrated compound. By dividing the moles of each substance by the smallest number of moles calculated, we obtain the simplest whole number ratio.
The formula of the hydrated sodium carbonate can then be written as Na2CO3·nH2O, where 'n' is the number obtained from the mole ratio representing the number of water molecules per formula unit of sodium carbonate.