Question

For questions 2 – 5, identify which of the three instruments (50 mL beaker, 10 mL graduated cylinder, or 100 mL graduated cylinder) you would use to measure the indicated quantities:

2. 95 mL of water

3. 4 mL of alcohol

4. 150 mL of salt water

5. 9.4 mL of hydrogen cyanide

6. What is a meniscus? How is the meniscus used for identification of volumetric measurements?

Answer 1

2. 95 mL of water is measured with the help of 100 mL graduated cylinder. Generally graduated cylinders are preferred over beaker for measurement because graduated cylinders are more accurate in comparison to beaker.

3. 4 mL of alcohol would measure with the help of 10 mL graduated cylinder.

4. 150 mL of salt water is accurately measured with the help of 100 mL graduated cylinder. Beaker is not use for accurate measurement that’s why we use graduated cylinders even for large volume.

5. 9.4 mL hydrogen cyanide would measure with the help of 10 mL graduated cylinder.

6. Meniscus is the curved boundary formed on the upper surface of any vessel, meniscus formed due to surface tension. It may be either convex or concave, depends upon liquid material inside the vessel. If there is mercury in vessel then it form convex meniscus and in case of water it would be concave.

For identification of volumetric measurements we should first observe the meniscus. If meniscus is concave then we read at the lower level of curve and when meniscus is convex we read it from upper level of the curve. During read ing meniscus we try to hold the vessel at ey level.