The major product in the following reaction is :

100 mL of 0.1 M HCl is taken in a beaker and to it 100 mL of 0.1 M NaOH is added in steps of 2 mL and the pH is continuously measured. Which of the following graphs correctly depicts the change in pH?

Three isomers A, B and C (mol. formula C₈H₁₁N) give the following results :
R has lower boiling point than S

A, B and C, respectively are :

The five successive ionization enthalpies of an element are 800, 2427, 3658, 25024 and 32824 kJ mol^–1. The number of valence electrons in the element is :