Which of the following properties remains identical for all isomers of a compound?

1. Structure

2. Physical properties

3. Chemical properties

4. Molecular formula

Which of the following pairs represents chain isomerism?

The compound having molecular formula C₄H₁₀O can show-

1. Metamerism

2. Functional isomerism 

3. Positional isomerism

4. All of the above

Tautomerism will be exhibited by                 

1. (CH₃)₃CNO               

2. (CH₃)₂NH

3. R₃CNO₂                   

4. RCH₂NO₂

Find the number of possible aromatic isomers with molecular formula C₇H₈O.
1. Three (3)
2. Five (5)
3. Seven (7)
4. Nine (9)