Question

an order is written for 250ml of a 2% solution. i have a 6% solution in stock.
how much stock solution and how much diluent are needed to compound this order.
my answer is 166.7 ml of 2% diluent and 83.3 ml stock of 6%stock
the previous answer said i was wrong but i am confused.

Answer 1

Your answer is actually correct! Here’s how to arrive at 166.7 ml of 2% diluent and 83.3 ml of 6% stock:

Let x be the amount of 6% solution needed. To get a 2% solution, we know that the amount of solute (in this case, the active ingredient) needs to be 2% of the total solution. So we can set up the equation:

0.06x = 0.02(250)

Simplifying, we get:

x = 83.3 ml

So we need 83.3 ml of the 6% stock solution. To find out how much diluent (such as water or saline) we need to add, we can subtract the volume of the stock solution from the desired total volume:

250 ml - 83.3 ml = 166.7 ml

Therefore, we need 166.7 ml of diluent to make up the rest of the 250 ml total volume, giving us a final solution that is 2% of the active ingredient.