Percent solution dilutions

[babyfeet]

I have to take a certification for the work that I have been doing for 15 years. For some reason they have a percent solution dilution for chemicals that are ordered now instead of made. This is one of the practice problems from the book I have that has this for an example of how to set it up. NOT VERY HELPFUL for a 44 year old brain.

% desired:100=g or mL needed:volume desired

this is the actual question 500mL of a 3% alcian blue in a 1% acidic acid. Figure the amount of solute needed for the question.

I have tried setting it up with the 3% of 500mL is _____ and that is as far as I have gotten.

 

[tkhunny]

You must find something that is in all pieces of your equation.

1) Amount of Acid in the original solution
2) Amount of Acid in what is added (maybe zero)
3) Amount of Acid in the final solution.

You can work the exact same problem using any component.

1) Amount of Non-Acid in the original solution
2) Amount of Non-Acid in what is added (maybe all of it)
3) Amount of Non-Acid in the final solution.

Please write the entire question and then pick a component to equate through the whole thing.

 

[mmm4444bot]

I have to take a certification for the work that I have been doing for 15 years.

I feel your pain.

For some reason they have a percent solution dilution for chemicals that are ordered now instead of made.

:roll:



% desired:100=g or mL needed:volume desired

Using a colon is one way to write a ratio. Writing a fraction is another way to write the same ratio.

In other words, the expression % desired : 100 denotes the following ratio.

$\displaystyle \frac{\text{\% desired}}{100}$

The expression g or ml needed : volume desired denotes the following ratio.

$\displaystyle \frac{\text{g or ml needed}}{\text{volume desired}}$


When two ratios have the same value, we call it a proportion.

$\displaystyle \frac{\text{\% desired}}{100} = \frac{\text{\text{g or ml needed}}}{\text{volume desired}}$

If you know any two out of the three quantities, the proportion above can be used to find the third quantity.



this is the actual question 500mL of a 3% alcian blue in a 1% acidic acid. Figure the amount of solute needed for the question.

We know two of the three numbers: 3 and 500.

Using the numbers from the given task, we write the proportion.

$\displaystyle \frac{3}{100} = \frac{\text{g needed}}{500}$

To solve this equation (i.e., find the third number), we multiply both fractions by 500 because that will eliminate the number 500 from the fraction on the righthand side.

$\displaystyle \frac{(500)(3)}{100} = \text{g needed}$

Next, 100 goes into 500 five times; so the 100 cancels, and the 500 becomes 5

$\displaystyle (5)(3) = \text{g needed}$

We see that 15g of alcian blue are needed to be disolved into 500mL of the 1% acid solution.

(Oh, by the way, numbers inside parentheses next to one another denotes multiplication. That is, (5)(3) means five times three.)



I have tried setting it up with the 3% of 500mL is _____ and that is as far as I have gotten.

Yes, this will also work.

Remember that "percent" means "per hundred".

Hence, the % symbol means "per 100", so 3% means "3 per 100" or 3/100.

If you divide 3 by 100 on a calculator, you get 0.03.

In other words, 3/100 is the rational form of 3%, and 0.03 is the decimal form of 3%.

We calculate 3% of 500 by multiplying 500 by either the rational form or the decimal form.

(0.03)(500) = 15

I worked about four years in a trauma center, and we had a small laboratory inside the emergency room for basic labwork.

"Percent solution" in medical labs means the number of grams of solid solute (or the number of milliliters of liquid solute) contained in 100mL of solution.

If I needed to mix 500mL of 3% alcian blue, here's how I would have calculated mentally.

3% solution means 3g per 100mL

I want five times as many mL, so I need 5 times 3g.


Good luck with your certification ~ Mark