22.472 g = mass MgCO3 + impurities
-18.42 g = mass MgO + impurities
-----------------
4.05 g = mass CO2 lost.
Convert mass CO2 to mass MgCO3 you started with.
4.05 g CO2 x (molar mass MgCO2/molar mass CO2) = ? g pure MgCO3 initially.
The problem tells you to round to the thousands place; however, your 18.42 is good only to the hundredths place. You may have inadvertently left a zero (or some other number) off the 18.42 g You may need to recalculate the 4.05 number if that's the case.
Then
A 22.472 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 18.42 g. Assuming that only the magnesium carbonate had decomposed, how much magnesium carbonate was present in the original sample? (round to thousandth place)
1 answer
1 answer