In which of the following compounds, the oxidation number of oxygen is +2?

• OF₂

• Na₂O

• NaO₂

• NaO₃

The monomer of natural rubber is

• Neoprene
  
  

• Isoprene
  
  

• Terylene
  
  

• Orlon

Which compound has the highest boiling point?

• n-pentane
  
  

• Isopentane
  
  

• Neopentane
  
  

• Isobutane

The number of $\mathrm{\pi }$-electrons in the molecules of aromatic compound is

• 4n
  
  

• 4n+1
  
  

• 4n+2
  
  

• 2n+4

Rutherford's alpha ($\mathrm{\alpha }$) particle scattering experiment resulted into the discovery of

• proton
  
  

• nucleus in the atom
  
  

• electron
  
  

• atomic mass

Which one of the following is not a heterogeneous mixture?

• Air
  
  

• Milk
  
  

• Smoke
  
  

• Jelly

Silk farming is known as

• Epiculture
  
  

• Pisciculture
  
  

• Sericulture
  
  

• Agriculture

Which of the following acids is also a vitamin?

• Formic acid
  
  

• Ascorbic acid
  
  

• Maleic acid
  
  

• Palmitic acid

19.

A metal M does not liberate hydrogen from acids but reacts with oxygen to give a black colour product. Identify M.

• Na
  
  

• Mg
  
  

• Cu
  
  

• Ca

One nanometer is equal to

• 10^-7cm

• 10^-8cm

• 10^-6m

• 10^-9m