Question

prelaboratory assignment

1. provide the key - term that corresponds to each of the following definitions.

(a) the amount of mass in a unit volume of matter; for example, 1.00 g/ml
(b) a procedure for obtaining the mass of a sample by first weighing a container and then weighing the container with the sample
(c) the degree of inexactness in an instrumental measurement
(d) to rinse glassware (e.g., a pipet) with a sample liquid to avoid dilution by water on the inside surface
(e) the clear lens at the surface of a liquid inside a graduated cylinder
(f) determining volume of a sample by measuring the volume of water displaced
key terms: condition, density, meniscus, uncertainty, volume by displacement, weighing by difference

1. a 10.0 - ml sample of liquid is pipetted into a 125 - ml flask with stopper. the mass of liquid is found to be 7.988 g. refer to example exercise 1 and calculate the density of the liquid.
2. state the volume of liquid shown in each of the following graduated cylinders.

Explanation:

1.

(a) Density is mass per unit volume. (b) Weighing by difference involves weighing container first then with sample to get sample mass. (c) Uncertainty represents inexactness in measurement. (d) Rinsing glass - ware with sample liquid is called conditioning. (e) The curved surface of liquid in cylinder is meniscus. (f) Measuring volume by water displacement is volume by displacement.

Step1: Recall density formula

The formula for density $
ho=\frac{m}{V}$, where $m$ is mass and $V$ is volume.

Step2: Substitute given values

Given $m = 7.988\ g$ and $V=10.0\ mL$. Then $
ho=\frac{7.988\ g}{10.0\ mL}=0.7988\ g/mL$.

Read the volume at the bottom of the meniscus. For the first cylinder, the meniscus is at 57 mL. For the second cylinder, the meniscus is at 60 mL.

Answer:

(a) density
(b) weighing by difference
(c) uncertainty
(d) condition
(e) meniscus
(f) volume by displacement

2.