Question

How many of the following oxides upon heating produce ${{O}_{2}}$ gas
1. $A{{g}_{2}}O$
2. $HgO$
3. $A{{u}_{2}}{{O}_{3}}$
4. $Pt{{O}_{2}}$
5. $Pb{{O}_{2}}$
6. $P{{b}_{3}}{{O}_{4}}$
7. $T{{l}_{2}}{{O}_{3}}$
8. $CuO$
9. $Mn{{O}_{2}}$
10. $Ba{{O}_{2}}$
11. $B{{i}_{2}}{{O}_{5}}$
12. $A{{l}_{2}}{{O}_{3}}$
(A) 11
(B) 8
(C) 6
(D) 10

Answer 1

In order to know which oxide, give oxygen gas on heating, we should know about their reactions which they undergo when exposed to heating. Moreover ,the oxides on heating undergo decomposition reactions i.e. they break down and give off metal and release oxygen gas on decomposition.

Complete step by step answer:
First of all, let’s discuss what oxides are. Oxides are formed by the action of the oxygen on the metals and the non-metals and thus, results in the formation of metallic and non-metallic oxides respectively. Simply we can say that oxides consist of one element and oxygen atom. When these metallic and the non- metallic oxides are exposed to heating, they undergo decomposition and result into the corresponding metal and non-metal along with the evolution of the oxygen gas. Now considering the statement; To know which of the following oxides give oxygen gas on heating, we need to write their reactions. The decomposition reactions of the following oxide when they are exposed to heating releases metal and oxygen gas are as follows;

Sr.no	Oxide	Decomposition reaction on heating
1.	$A{{g}_{2}}O$	The reaction occurs as:$A{{g}_{2}}O\xrightarrow{\Delta }Ag+{{O}_{2}}$
2.	$HgO$	The reaction occurs as:$HgO\xrightarrow{\Delta }2Hg+{{O}_{2}}$
3.	$A{{u}_{2}}{{O}_{3}}$	The reaction occurs as:$A{{u}_{2}}{{O}_{3}}\xrightarrow{\Delta }2Au+{{O}_{2}}$
4.	$Pt{{O}_{2}}$	The reaction occurs as:$Pt{{O}_{2}}\xrightarrow{\Delta }Pt+{{O}_{2}}$
5.	$Pb{{O}_{2}}$	The reaction occurs as:$Pb{{O}_{2}}\xrightarrow{\Delta }Pb+{{O}_{2}}$
6.	$P{{b}_{3}}{{O}_{4}}$	It doesn’t give oxygen gas on heating i.e. it doesn’t undergo decomposition.
7.	$T{{l}_{2}}{{O}_{3}}$	The reaction occurs as:$T{{l}_{2}}{{O}_{3}}\xrightarrow{\Delta }2Tl+{{O}_{2}}$
8.	$CuO$	The reaction occurs as:$CuO\xrightarrow{\Delta }Cu+{{O}_{2}}$
9.	$Mn{{O}_{2}}$	The reaction occurs as:$Mn{{O}_{2}}\xrightarrow{\Delta }Mn+{{O}_{2}}$
10.	$Ba{{O}_{2}}$	The reaction occurs as:$Ba{{O}_{2}}\xrightarrow{\Delta }Ba+{{O}_{2}}$
11.	$B{{i}_{2}}{{O}_{5}}$	The reaction occurs as:$B{{i}_{2}}{{O}_{5}}\xrightarrow{\Delta }2Bi+{{O}_{2}}$
12.	$A{{l}_{2}}{{O}_{3}}$	The reaction occurs as:$A{{l}_{2}}{{O}_{3}}\xrightarrow{\Delta }2Al+{{O}_{2}}$

So, thus all the oxides except the $P{{b}_{3}}{{O}_{4}}$ releases oxygen gas on heating.

Hence, option (a) is correct.

Note: All those compounds i.e. the oxides which consists of oxygen atom undergoes decomposition , thus liberating oxygen and the oxides are of three types i.e. acidic oxides like carbon dioxide etc. , basic oxides like potassium oxide etc. and amphoteric oxides ( which can act both as acidic or basic oxide)like zinc oxide etc.