Question

Oxide formation by heating element in oxygen atmosphere are best classified as which type of reaction?

a) Decomposition

b) Double displacement

c) Synthesis

d) None of the above

Answer 1

2CO(g)+O2(g)→2CO2(g)

oxidation number of Atoms in
CO
O = -2
C= +2

O2
O = 0
*********
Oxidation number of atoms in
CO2
C= +4
O=-2
*******************************

CuO(s)+2HCl(aq)→CuCl2(aq)+H2O(l)

oxidation number of atams in

CuO
Cu= +2
O=-2
--
HCl
H = +1
Cl=-1
*********
CUCl2
Cu= +2
Cl =-1

H2O
H= +1
O= -2
*****************************

2MnO4−(aq)+5SO2(g)+2H2O(l)→2Mn2+(aq)+5SO42−(aq)+4H+

oxidation number of atoms in

MnO4-

O = -2
Mn = +7

SO2

O= -2
S = +4

H2O

O =-2
H=+1

*******

oxidation number of atoms in
SO42-
O = -2
S= +6

Mn2+
Mn= +2

H+
H= +1
***************************

) Decomposition
one compound decomposes to give 2 or simple molecules AB --> A+B

b) Double displacement
cations and ions are getting interchanged in this process
AB + CD --> AC + BD
c) Synthesis
new compound is formed from simple molecules ; A+ B --> AB

heating element in oxygen
suppose Mg is heated

2Mg + O2 --> 2MgO ; new compound is formed . It is an example of synthesis

Answer
option c) Synthesis

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