5 Concentrations, Dilutions, and Reconstitution Free Online FlashCards

What does a concentration describe?

A concentration states the amount of ingredient in a stated amount of preparation; include the units, such as $\mathrm{mg/mL}$ or $\mathrm{g/100\ mL}$.

What does $2\%\ \mathrm{w/v}$ mean?

$2\%\ \mathrm{w/v}$ means $2\ \mathrm{g}$ of ingredient in each $100\ \mathrm{mL}$ of final solution.

What does $2\%\ \mathrm{w/w}$ mean?

$2\%\ \mathrm{w/w}$ means $2\ \mathrm{g}$ of ingredient in each $100\ \mathrm{g}$ of final mixture.

What does $5\%\ \mathrm{v/v}$ mean?

$5\%\ \mathrm{v/v}$ means $5\ \mathrm{mL}$ of ingredient in each $100\ \mathrm{mL}$ of final solution.

Convert $1\%\ \mathrm{w/v}$ to $\mathrm{mg/mL}$.

$1\%\ \mathrm{w/v}=1\ \mathrm{g/100\ mL}=10\ \mathrm{mg/mL}$.

What concentration is a $1:1{,}000\ \mathrm{w/v}$ solution?

A $1:1{,}000\ \mathrm{w/v}$ solution contains $1\ \mathrm{g}$ in $1{,}000\ \mathrm{mL}$, or $1\ \mathrm{mg/mL}$.

How do you calculate ingredient amount from concentration and volume?

Use $\text{amount of ingredient}=\text{concentration}\times\text{volume}$. For example, $20\ \mathrm{mg/mL}\times15\ \mathrm{mL}=300\ \mathrm{mg}$.

How do you find the volume containing a desired amount?

Use $\text{volume}=\text{desired amount}\div\text{concentration}$. At $20\ \mathrm{mg/mL}$, a $150\ \mathrm{mg}$ amount occupies $7.5\ \mathrm{mL}$.

What happens to ingredient amount during ordinary dilution?

Dilution lowers concentration by adding solvent or diluent while keeping the amount of ingredient constant.

What equation relates starting and final conditions in a dilution?

Use $C_1V_1=C_2V_2$, where $C_1,V_1$ are the starting concentration and volume, and $C_2,V_2$ are the desired final concentration and volume.

How much $40\ \mathrm{mg/mL}$ stock makes $100\ \mathrm{mL}$ at $10\ \mathrm{mg/mL}$?

Use $V_1=(C_2V_2)/C_1$: $(10\ \mathrm{mg/mL}\times100\ \mathrm{mL})/(40\ \mathrm{mg/mL})=25\ \mathrm{mL}$ of stock.

When preparing a specified final volume, how should diluent be measured?

Add diluent to bring the mixture to a final volume of $100\ \mathrm{mL}$. About $75\ \mathrm{mL}$ of diluent applies only if volumes are additive.