The number of significant figures in 0.00340 is ____________.

When 10 mL of an aqueous solution of Fe²⁺ ions was titrated in the presence of dil H₂SO₄ using diphenylamine indicator, 15 mL of 0.02 M solution of K₂Cr₂O₇ was required to get the end point. The molarity of the solution containing Fe²⁺ ions is x $$\times$$ 10^$$-$$2 M. The value of x is __________. (Nearest integer)

Consider the complete combustion of butane, the amount of butane utilized to produce 72.0 g of water is ___________ $$\times$$ 10^$$-$$1 g. (in nearest integer)

If the concentration of glucose (C₆H₁₂O₆) in blood is 0.72 g L^$$-$$1, the molarity of glucose in blood is ____________ $$\times$$ 10^$$-$$3 M. (Nearest integer)

[Given : Atomic mass of C = 12, H = 1, O = 16 u]