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

Silver (atomic weight = 108 g mol^-1) has a density of 10.5 g.cm^-3. The number of silver atoms on a surface of area 10^-12 m² can be expressed in scientific notation as y $$\times$$ 10^x. The value of x is?

2.68 $$\times$$ 10^-3 moles of a solution containing an ion Aⁿ⁺ require 1.61 $$\times$$ 10^-3 moles of $$MnO_4^-$$ for the oxidation of An⁺ to $$AO_3^-$$ in acid medium. What is the value of n?