Question

1.How many mg/mL does a 2.5% solution contain?

Answer 1

A 2.5% solution means that we have:

`2.5=\frac{\text{ weight of solute in kg}}{\text{weight of solvent in L}}\cdot100`

This basically means that:

`\frac{\text{ weight of solute in kg}}{\text{weight of solvent in L}}=(2.5)/(100)`

But we are being asked about mg/mL so we need to trnasform kg and L into mg and mL. We know that:

If we use this in the former equation we have:

`\begin{gathered} \frac{\text{ weight of solute in kg}}{\text{weight of solvent in L}}=\frac{\text{ weight of solute in mg}}{\text{weight of solute in mL}}\cdot(1000)/(1000000)=(2.5)/(100) \\ \frac{\text{ weight of solute in mg}}{\text{weight of solute in mL}}\cdot(1)/(1000)=(2.5)/(100) \\ \frac{\text{ weight of solute in mg}}{\text{weight of solute in mL}}=(2.5)/(100)\cdot1000=25 \end{gathered}`

Which basically means that this solution has 25mg of solute per each mL of solvent so the answer is:

`25(mg)/(mL)`