The concentration of the appetite regulating hormone ghrelin is about 1.3 x 10-9 m in the blood of a fasting person. how many molecules of ghrelin are in 1 l of blood?

7.826×10^14 molecules of ghrelin

Explanation:

Molarity of ghrelin = number of moles of ghrelin/volume of blood

number of moles of ghrelin = Molarity of ghrelin × volume of blood = 1.3×10^-9 × 1 = 1.3×10^-9 moles

From Avogadro's law

1 mole of a substance (ghrelin) contains 6.02×10^23 molecules

1.3×10^-9 moles of ghrelin contains 1.3×10^-9 × 6.02×10^23 = 7.826×10^14 molecules of ghrelin