10.0 mL of Na₂CO₃ solution is titrated against 0.2 M HCl solution. The following titre values were obtained in 5 readings :

4.8 mL, 4.9 mL, 5.0 mL, 5.0 mL and 5.0 mL

Based on these readings, and convention of titrimetric estimation the concentration of Na₂CO₃ solution is ___________ mM.

(Round off to the Nearest Integer).

The number of species below that have two lone pairs of electrons in their central atom is _________. (Round off to the Nearest Integer).

SF₄, BF$$_4^ - $$, ClF₃, AsF₃, PCl₅, BrF₅, XeF₄, SF₆

Consider the above reaction where 6.1 g of Benzoic acid is used to get 7.8 g of m-bromo benzoic acid. The percentage yield of the product is __________

(Round off to the Nearest Integer).

[Given : Atomic masses : C : 12.0 u, H : 1.0 u, O : 16.0 u, Br : 80.0 u]

The molar conductivities at infinite dilution of barium chloride, sulphuric acid and hydrochloric acid are 280, 860 and 426 S cm² mol^$$-$$1 respectively. The molar conductivity at infinite dilution of barium sulphate is _________ S cm² mol^$$-$$1. (Round off to the Nearest Integer ).