To find the volume of a solution delivered, especially in laboratory settings using instruments like a buret, you simply subtract the initial volume reading from the final volume reading. This method is fundamental for precise liquid dispensing, such as during a titration.
How to Precisely Determine Delivered Solution Volume
The process of finding the volume of a solution delivered is straightforward and relies on accurately measuring the liquid level before and after dispensing. This technique is commonly employed in chemistry laboratories, particularly for titration experiments, where the exact volume of a titrant delivered is crucial for calculations.
Steps to Calculate Volume Delivered from a Buret
The following steps outline the procedure for determining the precise volume of solution dispensed from a buret:
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Read the initial volume from the buret. Before beginning the delivery, carefully note the liquid level in the buret. This is your starting point, often read from the bottom of the meniscus (the curved surface of the liquid).
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Deliver the titrant into a receiving container. Open the stopcock of the buret to allow the solution (titrant) to flow into your reaction vessel (e.g., an Erlenmeyer flask). Control the flow rate carefully, especially as you approach the desired endpoint in a titration.
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Read the final volume from the buret. Once the delivery is complete (e.g., the titration endpoint is reached), close the stopcock and record the new liquid level in the buret. This is your ending point.
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Calculate the volume delivered using the equation below. The difference between the final and initial readings gives you the exact volume dispensed.
The formula for calculating the delivered volume is:
$$V{\text{delivered}} = V{\text{final}} - V_{\text{initial}}$$
Where:
- $V_{\text{delivered}}$ represents the total volume of solution that has been dispensed.
- $V_{\text{final}}$ is the volume reading on the buret after the solution has been delivered.
- $V_{\text{initial}}$ is the volume reading on the buret before the solution delivery began.
Practical Example
Let's illustrate with a common scenario in a chemistry lab:
Imagine you are performing a titration to determine the concentration of an unknown acid. You start with a buret filled with a standard base solution.
| Measurement Step | Buret Reading (mL) |
|---|---|
| Initial Volume ($V_{\text{initial}}$) | 0.85 |
| Final Volume ($V_{\text{final}}$) | 24.30 |
Using the formula:
$V{\text{delivered}} = V{\text{final}} - V{\text{initial}}$
$V{\text{delivered}} = 24.30 \text{ mL} - 0.85 \text{ mL}$
$V_{\text{delivered}} = 23.45 \text{ mL}$
Therefore, 23.45 mL of the base solution was delivered into the receiving container.
Key Considerations for Accuracy
- Meniscus Reading: Always read the volume from the bottom of the meniscus for clear liquids in glass burets. For colored solutions, read from the top of the meniscus.
- Eye Level: Ensure your eye is level with the meniscus to avoid parallax error, which can lead to inaccurate readings.
- Air Bubbles: Before starting, check for and remove any air bubbles in the buret tip, as they can cause inaccurate volume readings when dispensed.
- Proper Rinsing: Always rinse the buret with the solution it will contain before filling to ensure the concentration is not diluted by residual water or previous solutions.
By diligently following these steps and paying attention to detail, you can accurately determine the volume of any solution delivered, which is essential for reliable experimental results.
