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Mole concept and Stoichiometry — Chemistry STD 10 — Question

ICSE BoardEnglish MediumSTD 10ChemistryMole concept and Stoichiometry3 Marks
Question
Solid ammonium dichromate decomposes as :
$\left( NH _4\right)_2 Cr _2 O _7 \longrightarrow N _2+ Cr _2 O _3+4 H _2 O$
If $63 g$ of ammonium dichromate decomposes. Calculate the quantity in moles of $\left( NH _4\right)_2 Cr _2 O _7$
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Answer

Solid ammonium dichromate decomposes as:
$\left( NH _4\right)_2 Cr _2 O _7 \longrightarrow N _2+ Cr _2 O _3+4 H _2 O$
Molecular mass of ammonium dichromate
$=2(14+4)+104+112 $
$=252 g$
$\text { Number of moles }=\frac{\text { Weight }}{\text { Molecular weight }} $
$=\frac{63}{252} $
$=0.25 \text { moles }$

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