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]

4g equimolar mixture of NaOH and Na₂CO₃ contains x g of NaOH and y g of Na₂CO₃. The value of x is ____________ g. (Nearest integer)

250 mL of 0.5 M NaOH was added to 500 mL of 1 M HCl. The number of unreacted HCl molecules in the solution after complete reaction is ___________ $$\times$$ 10²¹. (Nearest integer)

(N_A = 6.022 $$\times$$ 10²³)