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# Gravimetric Analysis

APCHEM-KG8T4J

Metal carbonates are known to undergo thermal decomposition, producing the metal oxide and releasing carbon dioxide. The process is described by the following generic equation, in which $M$ represents an unknown divalent metal.

$$MC{ O }_{ 3 }(s) \overset{\Delta}{\rightarrow} MO(s)+{ CO }_{ 2 }(g)$$

A student wishes to identify the metal in a sample of an unknown metal carbonate. She weighs an empty crucible, adds a known mass of the unknown metal carbonate, and then heats the crucible and contents for 20 minutes in 5-minute intervals. She records the following data.

System Heating Time (Minutes) Mass (g)
Crucible empty N/A 26.40
Crucible + sample 0.0 28.56
Crucible + sample 5.0 28.12
Crucible + sample 10.0 27.74
Crucible + sample 15.0 27.68
Crucible + sample 20.0 27.68

$\$
She also plots the mass of the crucible and contents as a function of time.

Which of the following correctly describes the results of her experiment?

A
Mass of original sample 2.16 g
Mass of $CO_{2}$ driven off 0.88 g
Mass of metal oxide remaining 1.28 g
Mass of metal, M, in original sample 0.96 g
Molar mass of metal M 48 g/mol
Identity of metal M Titanium
B
Mass of original sample 28.56 g
Mass of $CO_{2}$ driven off 0.88 g
Mass of metal oxide remaining 27.68 g
Mass of metal, M, in original sample 1.28 g
Molar mass of metal M 64 g/mol
Identity of metal M Copper
C
Mass of original sample 28.56 g
Mass of $CO_{2}$ driven off 0.88 g
Mass of metal oxide remaining 27.68 g
Mass of metal, M, in original sample 1.28 g
Molar mass of metal M 32 g/mol
Identity of metal M Sulfur
D
Mass of original sample 2.16 g
Mass of $CO_{2}$ driven off 0.88 g
Mass of metal oxide remaining 1.28 g
Mass of metal, M, in original sample 0.64 g
Molar mass of metal M 32 g/mol
Identity of metal M Sulfur