You are a work study student in our chemistry department. Amy, your supervisor has just asked you to prepare 250ml of 0.500M H3PO4 solution for tomorrow's undergraduate experiment. The Stock Solutions cabinet is under the Stockroom Explorer. You will find find a 2.50 liter bottle containing 14.6M H3PO4. Please prepare a flask containing 250ml of a 0.500M solution. To ensure proper credit, please write your calculations in the space given below.
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In designing your procedure, it is useful to remember that diluting a substance does not change the amount of that substance. So the number of moles of the substance before the dilution is the same as the number of moles after the dilution (conservation of matter). The number of moles in solution is given by the concentration (C in moles/liter) multiplied by the volume (V in liters). So the conservation of matter implies:
C1V1 = C2V2
where C is concentration and V is volume. 1 labels the solution before the dilution and 2 labels the solution after the dilution. (This expression is based on the number of moles of the substance between the same before and after the dilution, with C (moles/liter) * V (liter) = moles).
Important: Please describe your complete procedure and the key quantities you measure. Points are based on whether or not you explain your procedure in sufficient detail for us to know what you did. You are not graded on the method you used; all approaches that produce accurate results are fine.
Given, we need to prepare 250 mL of 0.500 M H3PO4 solution.
First, let's calculate the required volume of the concentrated 14.6 M H3PO4 solution that we need to dilute to get the required 250 mL of 0.500 M solution.
Using the dilution formula, C1V1 = C2V2, where C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration, and V2 is the final volume.
C1 = 14.6 M (initial concentration of concentrated H3PO4)
V1 = We need to find this (volume of concentrated H3PO4 required)
C2 = 0.500 M (final concentration needed in the 250 mL flask)
V2 = 0.250 L (final volume needed, since 250 mL = 0.250 L)
Plugging in these values into the equation:
14.6 M * V1 = 0.500 M * 0.250 L
Now, solve for V1:
V1 = (0.500 M * 0.250 L) / 14.6 M
V1 = 0.125 / 14.6
V1 ≈ 0.00856 L
To convert this to milliliters, multiply by 1000:
V1 ≈ 8.56 mL
Now we have the required volume of the concentrated H3PO4 solution.
Procedure:
1. Put on proper lab safety gear, including gloves, goggles, and a lab coat.
2. Take a clean, dry 250 mL volumetric flask and a burette.
3. Using a pipette, carefully measure out approximately 8.56 mL of the 14.6 M H3PO4 from the 2.50 L stock bottle.
4. Transfer this measured volume of concentrated H3PO4 into the 250 mL volumetric flask.
5. Slowly add distilled water (deionized water) to the volumetric flask, rinsing the sides of the flask and making sure any residual H3PO4 is washed into the solution.
6. Fill the flask with distilled water up to the 250 mL mark. Mix the solution well by inverting the flask several times.
7. You now have a 250 mL flask containing a 0.500 M H3PO4 solution.
8. Label the flask with the concentration, date, and your name.
Calculations summary:
Initial concentration (C1) = 14.6 M
Final concentration (C2) = 0.500 M
Final volume (V2) = 0.250 L
Required volume of concentrated H3PO4 (V1) = 8.56 mL
To prepare a 250ml 0.500M H3PO4 solution from the 14.6M H3PO4 stock solution, we can use the equation C1V1 = C2V2, where C1 and V1 represent the initial concentration and volume of the stock solution, and C2 and V2 represent the final concentration and volume of the desired solution.
Let's calculate the required volume of the stock solution we need to dilute. Rearranging the equation, we have V1 = (C2V2) / C1.
Given:
C1 = 14.6M (concentration of stock solution)
V2 = 0.250L (final volume of the desired solution)
C2 = 0.500M (final concentration of the desired solution)
Plugging in these values, we can calculate V1 as follows:
V1 = (0.500M * 0.250L) / 14.6M
V1 ≈ 0.00862L or 8.62mL
So, we need to measure 8.62mL of the stock solution using a pipette or a graduated cylinder.
To prepare the 0.500M H3PO4 solution, follow these steps:
1. Label a clean, dry 250mL flask to signify that it contains the 0.500M H3PO4 solution.
2. Using a pipette or a graduated cylinder, measure 8.62mL of the 14.6M H3PO4 stock solution.
3. Pour the measured stock solution into the labeled flask.
4. Add distilled water to the flask slowly while swirling gently until the total volume reaches approximately 250mL.
5. Verify that the meniscus (the curved surface of the liquid) is at the calibration mark of 250mL on the flask.
6. Close the flask with its cap or a stopper so that the solution is secure and won't spill.
Please note that it's essential to be precise in measuring the stock solution and adding the correct volume of water to achieve the desired concentration. Also, ensure you mix the solution thoroughly to obtain a homogenous mixture.
To prepare 250ml of a 0.500M H3PO4 solution using the 14.6 M H3PO4 stock solution, we can use the dilution formula C1V1 = C2V2, where C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration, and V2 is the final volume.
Given:
C1 = 14.6 M (concentration of stock solution)
V1 = 2.50 L (volume of stock solution)
C2 = 0.500 M (desired concentration)
V2 = 0.250 L (desired volume)
Using the dilution formula, we can rearrange to solve for V1:
V1 = (C2 * V2) / C1
Substituting the given values into the equation:
V1 = (0.500 M * 0.250 L) / 14.6 M
V1 = 0.0086 L
So, to prepare 250ml of the 0.500M H3PO4 solution, we need to measure 0.0086 liters (or 8.6 ml) of the 14.6 M H3PO4 stock solution and add it to a 250 ml flask. Then, we can fill the flask with distilled water up to the 250 ml mark.
Procedure:
1. Measure 8.6 ml of the 14.6 M H3PO4 stock solution using a pipette or graduated cylinder.
2. Transfer the measured volume of the stock solution into a 250 ml flask.
3. Fill the flask with distilled water up to the 250 ml mark.
4. Gently swirl or mix the flask to ensure proper mixing of the solution.
5. The resulting solution in the flask will be 250 ml of a 0.500M H3PO4 solution.
Remember to wear appropriate PPE (personal protective equipment) and handle chemicals safely.