Solving 'How Much Solution' Problems: Minoxidil Example

  • Thread starter Marlona Ely
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In summary, the question is about finding the amount of 4% solution needed to be added to 50 ml of 1% solution to obtain a 2% solution of minoxidil. The set up for the problem involves using the percentages and the given quantities to solve for the unknown quantity.
  • #1
Marlona Ely
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Help with one of those "how much solution to equal a percentage of acid" problems!

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My problem seems to be in just how to set up the table. Once I get the figures plugged in, I can seem to work the problem. The question asks:

Minoxidil is a drug that has recently proven to be effective in treating male pattern baldness. A pharmacist wishes to mix a solution that is 2% minoxidil. She has on hand 50 ml of a 1% solution, and she wishes to add some 4% solution to it to obtain the desired 2% solution. How much 4% solution should she add?

I've set it up like: .01 50 50(.01)
.04 x x(.04)
-02 x+50 .02(x+50)

50(.01) +x(.04) = .02(x+50)

Is this the correct way to set it up?
 
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Looks good to me!
 
  • #3


Yes, you have set up the problem correctly. You have correctly identified the known quantities (50 ml of 1% solution and 4% solution to be added) and the unknown quantity (the amount of 4% solution to be added). Your setup of the table is also correct, with the concentration, volume, and total amount for each solution.

To solve the problem, you can use the equation you have set up: 50(.01) +x(.04) = .02(x+50). This equation represents the total amount of minoxidil in the final solution, which should be equal to the desired 2% concentration.

To solve for x, you can first distribute the .02 on the right side of the equation: 50(.01) + x(.04) = .02x + 1. Then, you can subtract .02x from both sides and combine like terms: 50(.01) - .02x = 1. Finally, you can divide both sides by .02 to isolate x: x = (50(.01) - 1)/.02 = 25 - 1/.02 = 25 - 50 = -25.

This means that the pharmacist would need to add -25 ml of the 4% minoxidil solution to the 50 ml of 1% solution to obtain a final solution of 2% minoxidil. However, since negative volume does not make sense, we can conclude that there is no solution to this problem. The pharmacist would need to obtain a 4% solution with a larger volume to mix with the 50 ml of 1% solution to obtain the desired 2% concentration.

I hope this helps with your understanding of how to solve "how much solution" problems. Remember to always clearly identify the known and unknown quantities, set up the table correctly, and use an equation to solve for the unknown quantity.
 

1. How do I calculate the amount of solution needed for a specific concentration?

To calculate the amount of solution needed for a specific concentration, you can use the formula: amount of solution = (desired concentration / stock concentration) x volume of stock solution. In the case of Minoxidil, if you want a 2% concentration and have a stock solution of 5%, you would need 0.4mL of stock solution for every 1mL of desired solution.

2. What is the difference between volume and concentration in a solution?

Volume refers to the amount of space a solution takes up, while concentration refers to the amount of solute (substance being dissolved) in a given volume of solution. Volume is typically measured in mL or L, while concentration is measured in molarity (moles solute/ liter solution) or percentage (%).

3. How can I check the accuracy of my calculations for a solution?

You can check the accuracy of your calculations by using a balance to measure the mass of the solute and a graduated cylinder to measure the volume of solution. Make sure to use the appropriate units (grams for mass, mL for volume) and compare your results to the expected values.

4. Can I use any type of container to make a solution?

While any container can technically be used to make a solution, it is important to use a container that is clean and has accurate volume markings. Graduated cylinders and beakers are commonly used for making solutions, but it is important to calibrate them regularly to ensure accurate measurements.

5. What is the best way to mix a solution?

The best way to mix a solution is to add the solute to the solvent (usually water) and stir until it is completely dissolved. It is important to stir gently to avoid splashing or losing any solution. It may also be helpful to use a magnetic stir bar or stir plate to ensure thorough mixing.

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