Answer :
Answer:
To obtain 0.5 milliliters (mL) of hydrochloric acid (HCl) using a 10-milliliter (mL) graduate calibrated from 2 to 10 mL in 1-mL divisions, you can use the aliquot method. Here is a step-by-step explanation of the process:
Aliquot Method Overview
The aliquot method involves diluting a larger, measurable volume of the solution to a specific concentration, then taking a portion of this diluted solution to achieve the desired volume. This method is useful when the required volume is too small to be measured accurately with available equipment.
Steps to Obtain 0.5 mL of Hydrochloric Acid
Preparation of Diluted Solution:
First, decide on a convenient dilution factor. A common choice is a 10-fold dilution, which makes calculations simple and ensures accurate measurements.
Measure a larger, accurately measurable volume of HCl, such as 5 mL. Since your graduate is calibrated in 1-mL increments, you can easily measure 5 mL.
Diluting the Hydrochloric Acid:
Prepare a clean container for the dilution (e.g., a beaker or another graduated cylinder).
Add the 5 mL of hydrochloric acid to this container.
Dilute this 5 mL of HCl with distilled water to a total volume of 50 mL. This gives you a 1:10 dilution (since 5 mL HCl + 45 mL water = 50 mL total volume).
Ensure thorough mixing of the solution to achieve uniform concentration.
Measuring the Desired Aliquot:
Now that you have a 1:10 diluted solution, you need to measure out an aliquot of this solution that will give you the equivalent of 0.5 mL of the original hydrochloric acid.
Calculate the volume of the diluted solution that contains 0.5 mL of the original HCl:
Volume of diluted solution
=
0.5
mL
0.1
=
5
mL
Volume of diluted solution=
0.1
0.5 mL
=5 mL
This calculation is based on the fact that the diluted solution is 1/10th the concentration of the original, so 5 mL of the diluted solution will contain the same amount of HCl as 0.5 mL of the original solution.
Final Measurement:
Using your 10-mL graduate, measure 5 mL of the diluted hydrochloric acid solution.
This 5 mL portion of the diluted solution now represents 0.5 mL of the original, concentrated hydrochloric acid.
Summary
By diluting 5 mL of hydrochloric acid to 50 mL total volume and then taking 5 mL of this diluted solution, you effectively obtain the desired 0.5 mL of HCl. This approach leverages the higher accuracy of measuring larger volumes to achieve an accurate small volume via dilution.
Practical Considerations
Accuracy: Ensure that all measurements are as accurate as possible. Use a pipette for more precise measurement if available.
Mixing: Mix the diluted solution thoroughly to ensure uniform concentration before taking the final aliquot.
Clean Equipment: Use clean and dry equipment to avoid contamination and ensure accurate measurements.
