A 23.9475 g sample of impure magnesium carbonate
was heated to complete decomposition
according to the equation
MgCO3(s) → MgO(s) + CO2(g).
After the reaction was complete, the solid
residue (consisting of MgO and the original
impurities) had a mass of 18.345 g. Assuming
that only the magnesium carbonate had decomposed,
how much magnesium carbonate
was present in the original sample?
Answer in units of g.
Thank you!!!
To find the amount of magnesium carbonate present in the original sample, we need to calculate the difference in mass before and after the reaction.
The mass of the sample before the reaction = 23.9475 g
The mass of the residue after the reaction = 18.345 g
The mass of the magnesium carbonate can be calculated by subtracting the mass of the residue from the mass of the original sample:
Mass of magnesium carbonate = Mass of sample before reaction - Mass of residue
= 23.9475 g - 18.345 g
= 5.6025 g
Therefore, there was 5.6025 g of magnesium carbonate present in the original sample.
To find the mass of magnesium carbonate present in the original sample, we need to calculate the mass of the magnesium carbonate that decomposed.
First, we need to find the mass of magnesium oxide (MgO) formed during the decomposition. To do this, we subtract the mass of the residue (18.345 g) from the initial mass of the sample (23.9475 g):
Mass of MgO = Initial mass - Residue mass
= 23.9475 g - 18.345 g
= 5.6025 g
Next, we need to find the molar mass of MgO. Magnesium has a molar mass of 24.31 g/mol, and oxygen has a molar mass of 16.00 g/mol. Adding these masses gives the molar mass of MgO:
Molar mass of MgO = 24.31 g/mol + 16.00 g/mol
= 40.31 g/mol
Now, we can calculate the number of moles of MgO formed:
Number of moles of MgO = Mass of MgO / Molar mass of MgO
= 5.6025 g / 40.31 g/mol
= 0.1389 mol
Since the equation tells us that one mole of magnesium carbonate (MgCO3) gives one mole of MgO, we can conclude that the number of moles of magnesium carbonate decomposed is also 0.1389 mol.
Finally, we can calculate the mass of magnesium carbonate decomposed by multiplying the number of moles by the molar mass of MgCO3:
Mass of MgCO3 = Number of moles of MgCO3 × Molar mass of MgCO3
= 0.1389 mol × (24.31 g/mol + 12.01 g/mol + 3 × 16.00 g/mol)
= 0.1389 mol × 84.32 g/mol
= 11.708 g
Therefore, the mass of magnesium carbonate present in the original sample is 11.708 g.
initial mass - final mass = CO2 mass
convert CO2 mass to moles
CO2 moles = MgCO3 moles
convert MgCO3 moles to MgCO3 mass