A weighed sample of crystalline sodium carbonate (Na2CO3.nH2O)was heated in a crucible until there was no further change in mass.The mass of the sample reduced by 14.5%.Calculate the number of moles (n) of the water of crystallization.
To calculate the number of moles of water of crystallization (n), we first need to calculate the change in mass.
Change in mass = Initial mass - Final mass
= 100% - 14.5%
= 85.5%
Next, we convert the percentage change in mass to a decimal:
Change in mass (decimal) = 85.5% / 100
= 0.855
Now, we can calculate the number of moles of water using the formula:
n = (Change in mass / Molar mass of water) / (Change in mass / Molar mass of water + Molar mass of anhydrous compound)
The molar mass of water (H2O) = 2 * (atomic mass of hydrogen) + atomic mass of oxygen
= 2 * 1 + 16
= 18 g/mol
The molar mass of anhydrous compound (Na2CO3) = 2 * (atomic mass of sodium) + atomic mass of carbon + 3 * (atomic mass of oxygen)
= 2 * 23 + 12 + 3 * 16
= 106 g/mol
Substituting the values into the formula:
n = (0.855 / 18) / (0.855 / 18 + 106)
= 0.0475 / (0.0475 + 106)
= 0.0475 / 106.0475
≈ 0.000448 mol
Therefore, the number of moles (n) of water of crystallization is approximately 0.000448 mol.