If the value of Avogadro number is 6.023 $$\times$$ 10²³ mol^-1 and the value of Boltzmann constant is 1.380 $$\times$$ 10^-23 J K^-1, then the number of significant digits in the calculated value of the universal gas constant is

29.2 % (w/w) HCl stock solution has density of 1.25 g mL^-1 . The molecular weight of HCl is 36.5 g mol^-1 . The volume (mL) of stock solution required to prepare a 200 mL solution of 0.4 M HCl is

A student performs a titration with different burettes and finds titre values of 25.2 mL, 25.25 mL, and 25.0 mL. The number of significant figures in the average titre value is