Rank these solutions from the most alkaline (1) to the least alkaline (5). poh = 0.5 ph = 3.5 [oh–] = 5.62 × 10–5 m [h3o+] = 3.16 × 10–7 m ph = 0.5

I am pretty sure the more alkaline a solution is the basic it is.  Using that definition you can, you can compare the pH values for each of the solutions and the ones that have the highest pH values will be the most alkaline (basic) and the ones with the lowest pH values will be the least alkaline (acidic). pH=[H₃O⁺] and pH=14-pOH (use pOH=[OH⁻])
pH=14-0.5=13.5
pH=3.5
pH=14-(-log(5.62x10^-5))=9.75
pH=-log(3.16x10^-7)=6.5
pH=0.5
ordered from most alkaline to least:
pOH=0.5, [OH]=5.62x10^-5, [H₃O⁺]=3.16x10^-7, pH=3.5, pH=0.5

Hope this helps.  Let me know if you have any further questions in the comments.

Dissociation then hydration dissolving

Density and pressure