Octane number of petrol can be improved by admixing it with which of the following chemicals?

• Et₄Pb

• CH₃OC(CH₃)₃

• Both (a) and (b)

• Pyrene

Cyclohexane, methylcyclopentane, 1, 3-dimethyl cyclobutane and 1, 2, 3-trimethyl cyclopropane are examples of which one of the following? 

• Constitutional isomers

• Structural isomers

• Both (a) and (b)

• Structural as well as positional isomers

How many structural isomers are possible for a molecule of C₆H₁₂,composition but having at least-one carbocyclic ring?

• Seven

• Six

• Five

• None of these 

24.

The configurations of the chiral centres in A and B are, respectively, as

                          

 

• R and S

• S and R

• R and R

• S and S

Arrange Na⁺, Mg⁺ and Al³⁺ in increasing order of energy of hydration.

• Na⁺ < Mg⁺ < Al³⁺

•  Al³⁺<  Mg⁺ < Na⁺

• Al³⁺ < Na⁺ < Mg²⁺

• Mg²⁺< Al³⁺ < Na⁺

Which one of K, I, Cl and Li will display the highest first ionisation energy?

• K

• I

• Cl

• Li

You may have noticed that chicken-egg is very strong along its long axis so much so that it does not break even when pressed very hard. Which of the following is the main constituent of egg-shell?

• CaSO₄·2H₂O

• CaSO₄·1/2H₂O

• CaSiO₃

• CaCO₃

Nuclear attraction is often the deciding control factor for the association of neutral molecules to a given metal ion. Which one of the following represents the correct order of stability of the ions?

[Be(H₂O)₄]²⁺, [Mg(H₂O)₄]²⁺, [Ca(H₂O)₄]²⁺ and [Sr(H₂O)₄]²⁺ ?

• [Be(H₂O)₄]²⁺ > [Sr(H₂O)₄]²⁺> [Mg(H₂O)₄]²⁺ > [Ca(H₂O)₄]²⁺

• [Ca(H₂O)₄]²⁺> [Mg(H₂O)₄]²⁺ > Be(H₂O)₄]²⁺  > [Sr(H₂O)₄]²⁺

• [Sr(H₂O)₄]²⁺ > [Ca(H₂O)₄]²⁺> [Mg(H₂O)₄]²⁺ > Be(H₂O)₄]²⁺

• [Be(H₂O)₄]²⁺> [Mg(H₂O)₄]²⁺ >  [Ca(H₂O)₄]²⁺ > [Sr(H₂O)₄]²⁺

Which of the following represents correct acidity order Li₂O , BeO and B₂O₃ ?

• Li₂O < BeO < B₂O₃

• B₂O₃ < BeO < Li₂O

• BeO < Li₂O < B₂O₃

• BeO < B₂O₃ < Li₂O

Which of the following does not/do not represent the correct equivalent mass of Cr₂O${}_7^{2-}$ in the reaction Cr₂O${}_7^{2-}$+ 14 H⁺ + 6e^- → 2Cr³⁺ + 7H₂O.

• The molar mass of dichromate

• One third of the molar mass of dichromate

• One half of the molar mass of dichromate

• all of the above