Question

If there were 60,000 molecules of a tripeptide in 1.0 nanolitre (nl) of solution, what would the tripeptide concentration be?

express your numerical answer in nmoles/L

Answer 1

number of moles= number of molecules/ Avogadro number

Avogadro number= 6.022 $\times$ 10^23

number of moles= 60000/ 6.022 $\times$ 10^23

= 9.96$\times$10^-20

1 mole= 10^9 nmoles

9.96$\times$10^-20 moles= 9.96$\times$10^-20$\times$10^9=9.96$\times$10^-11 nmoles

1 L= 10^9 nL

so 1 nL= 10^-9 L

concentration= number of nmoles/ volume of the solution in litres

=9.96$\times$10^-11 nmoles/10^-9L

= 9.96$\times$10^-2 nmoles/L