Chemistry - Stoichiometry Question with Solution | TestHub

ChemistryStoichiometryBasic Methods of Calculations (POAC, LR)Medium2 minQB

ChemistryMediuminteger

Igniting $MnO_{2}$ converts it quantitatively to $Mn_{3} O_{4}$ . A sample of pyrolusite is of the following composition: $MnO_{2} 80%, SiO_{2}$ and other inter constituents $15%$ , rest being water. The sample is ignited in air to constant weight. What is the percentage of Mn in the ignited sample ?

[At. Wt. of O = 16, Mn = 54.9]

Answer:

Solution:

$MnO_{2}$ on ignition converts into $Mn_{3} O_{4}$

⇒ Applying POAC for Mn

$(\frac{80}{87}) \times 1 = (\frac{x}{229}) \times 3$

$x = 70.191$

weight of Residue $= 70.191 + 15 = 85.191$

$%$ of Mn in the ignited sample $= \frac{( \frac{80}{87} ) \times 55}{85.191} \times 100 = 59.33 \approx 59$

Stream:JEESubject:ChemistryTopic:StoichiometrySubtopic:Basic Methods of Calculations (POAC, LR)

⏱ 2mℹ️ Source: QB

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Chemistry - Stoichiometry Question with Solution | TestHub

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