2.0 THE MOLE: Empirical and Molecular formula

2.10 Volumetric analysis

Determining quantities such as mass and molarity by measuring volumes of solutions is called volumetric analysis. Volumes of solutions are measured using a pipette (10ml or 25ml) and burette, which are shown in Figure 2.10. Accurate reading of scales is extremely important.

When taking readings, the eye should be close to and at the level of the bottom of the meniscus.

Questions 2.10

1. Where a base and acid are involved, it is normally the base that is sucked, not the acid. Suggest a reason for this.
2. Once the liquid level reaches the mark, sucking is stopped and the mouth of the pipette is blocked air-tight using a thumb. How is the content of pipette transferred into a conical flask once sucked?
3. Can a pipette measure other volumes apart from what is indicated on its bulb? Explain.
4. Study the burette scale. What is the maximum volume a burette can measure?
5. How many small divisions are there between 0 and 1 ml marks on a burette?
6. What volume does each small division represent?
7. To what decimal place in ml can we measure volume using a burette?
8. What are the only possible values of the last decimal number?
9. Based on you knowledge of using the millimeter scale on a ruler, report the readings represented by V₁, V₂ and V₃.

Answers to Questions 2.10

While reading a scale, we can only estimate the middle or near the middle (¹/₂) of the smallest division and not ¹/₃, ¹/₄ or any other fraction of it. For example, a reading can be 20.10 ml, 20.15 ml or 20.20 ml but nothing else in between.