what is the formula for the sodium sulfate if 3.54g of dry solid remain after 8.50g of hydrate are heated??
hydrate ==> anhydrous + H2O
..8.50g......3.54.......4.96
mols Na2SO4 = 3.54/142 = about 0.0249
mols H2O = 4.96/18 = about 0.275
0.0249/0.0249 = 1.000
0.275/0.0249 = 11.0
empirical formula is Na2SO4.11H2O based on these data.
thank you, very helpful
To find the formula for sodium sulfate, we need to determine the ratio between the anhydrous compound (dry solid) and the hydrated compound (hydrate) by using the given information.
First, let's calculate the mass of water that was present in the hydrate:
Mass of water = Mass of hydrate - Mass of dry solid
Mass of water = 8.50g - 3.54g
Mass of water = 4.96g
Next, we need to find the number of moles for both the anhydrous compound and water. Since we have the mass of each substance, we can use their molar masses.
The molar mass of sodium sulfate (Na2SO4) is:
Na: 22.99 g/mol (sodium)
S: 32.07 g/mol (sulfur)
O: 16.00 g/mol (oxygen) x 4 (since there are four oxygen atoms in the formula)
Molar mass of Na2SO4:
= 22.99 g/mol + 32.07 g/mol + (16.00 g/mol x 4)
= 142.04 g/mol
Now, we can calculate the number of moles for both the anhydrous compound and water:
Number of moles of anhydrous compound = Mass of dry solid / Molar mass of Na2SO4
Number of moles of anhydrous compound = 3.54g / 142.04 g/mol
Number of moles of anhydrous compound ≈ 0.025 mol
Number of moles of water = Mass of water / Molar mass of H2O
Number of moles of water = 4.96g / 18.02 g/mol (molar mass of water)
Number of moles of water ≈ 0.275 mol
Now, we can determine the ratio between the anhydrous compound and water by dividing the number of moles of anhydrous compound by the number of moles of water:
Ratio = Number of moles of anhydrous compound / Number of moles of water
Ratio = 0.025 mol / 0.275 mol
Ratio ≈ 0.091
Since the ratio is approximately 0.091, we can infer that the formula of sodium sulfate is Na2SO4·9H2O. This means that each formula unit of sodium sulfate is associated with nine water molecules.