the quantity in moles of ( {\NH}_4) _2 {\Cr}_2 {\O}_7 if 63 {\gm} of ( {\NH}_4) _2 {\Cr}_2 {\O}_7 is heated.

ICSE Class 10 Chemistry 2015 Solved Paper - Question 60

Consider the following reaction and based on the reaction answer the questions that follow :

( {\NH}_4) _2 {\Cr}_2 {\O}_7 \ {─────▸}↖{\;\text " heat "\;} {\N}_2( {\g})+4 {\H}_2 {\O}( {\g})+ {\Cr}_2 {\O}_3

Calculate:

Question : 60 of 85

Marks: +1, -0

the quantity in moles of

( {\NH}_4) _2 {\Cr}_2 {\O}_7

63 {\gm}

( {\NH}_4) _2 {\Cr}_2 {\O}_7

is heated.

Solution:

\table ( {\NH}_4) _2 {\Cr}_2 {\O}_7, \ { ───▸}↖{∆},\; {\N}_2 ↑,+,4 {\H}_2 {\O},+,\; {\Cr}_2 {\O}_3 ; 2(14+4)+(52 × 2) ,,= 2 × 14\;,,,,=2 × 52;+(16 × 7),,=28 {\gm},,,,+3 × 16 ;=36+104+112=252 {\gm},,,,,,=152 {\gm}

\;\text " No. of Moles "\;\;=\;{\;\text " Wt. of "\; ( {\NH}_4) _2 {\Cr}_2 {\O}_7}/{\;\text " Gram. Mol. Mass "\;}

\;=\;{63}/{252}=0.25 \;\text " moles "\;

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