A 15.67gsample of hydrate of magnesium carbonate was carefully heated, without decomposing the carbonate to drive off water. The mass was reduce to 7.58g. What is the formula of the hydrated?
To determine the formula of the hydrated magnesium carbonate, we need to first calculate the mass of water lost during heating.
Initial mass of hydrated magnesium carbonate = 15.67 g
Final mass after heating = 7.58 g
Mass of water lost = Initial mass - Final mass
Mass of water lost = 15.67 g - 7.58 g
Mass of water lost = 8.09 g
Now, we can calculate the number of moles of water lost using the formula:
Number of moles = Mass / molar mass
Molar mass of water (H2O) = 18.015 g/mol
Number of moles of water lost = 8.09 g / 18.015 g/mol
Number of moles of water lost ≈ 0.4492 mol
Next, we need to calculate the number of moles of magnesium carbonate in the sample. Since the hydrated magnesium carbonate contains magnesium carbonate and water, we subtract the moles of water lost from the total moles of the sample.
Total moles of the sample = Mass / molar mass
Molar mass of hydrated magnesium carbonate = 15.67 g/mol
Molar mass of magnesium carbonate = 84.313 g/mol
Total moles of the sample = 15.67 g / 84.313 g/mol
Total moles of the sample ≈ 0.1856 mol
Moles of magnesium carbonate = Total moles - Moles of water lost
Moles of magnesium carbonate ≈ 0.1856 mol - 0.4492 mol
Moles of magnesium carbonate ≈ -0.2636 mol
Given that the moles of magnesium carbonate are negative, it indicates an error in the calculations. Please double-check the given data and re-calculate accordingly.
To determine the formula of the hydrate of magnesium carbonate, we need to first calculate the amount of water that was driven off by heating the sample.
Given:
Mass of the hydrated sample = 15.67 g
Mass of the sample after heating = 7.58 g
1. Calculate the mass of water lost:
Mass of water lost = Mass of the hydrated sample - Mass of the sample after heating
= 15.67 g - 7.58 g
= 8.09 g
2. Calculate the molar mass of water (H2O):
The molar mass of water (H2O) is approximately 18.015 g/mol.
3. Calculate the number of moles of water lost:
Number of moles of water lost = Mass of water lost / Molar mass of water
= 8.09 g / 18.015 g/mol
≈ 0.45 mol
4. Determine the number of moles of magnesium carbonate:
The molar mass of magnesium carbonate (MgCO3) is approximately 84.313 g/mol.
Moles of MgCO3 = Mass of the sample after heating / Molar mass of MgCO3
= 7.58 g / 84.313 g/mol
≈ 0.09 mol
5. Calculate the ratio between moles of water lost and moles of magnesium carbonate:
Ratio = Moles of water lost / Moles of magnesium carbonate
= 0.45 mol / 0.09 mol
= 5 mol
The ratio of water to magnesium carbonate is 5:1, which means that for every 5 moles of water, there is 1 mole of magnesium carbonate. Therefore, the formula of the hydrate of magnesium carbonate is MgCO3·5H2O.
15.67g = mass MgCO3.xH2O
-7.68 g = mass MgCO3
--------
xxxxx = mass H2O
mols H2O = grams/molar mass
mols MgCO3 = grams/molar mass
Find ratio of 1 mol MgCO3 to x mols H2O. That will be the empirical formula of the hydrate.