CHEM 11: Density Lab Quiz

In Part A you will determine the density of a liquid.

This liquid is

Distilled Water

You will determine the density of this liquid three times, each time using an electronic balance to measure mass, but each time using a different device to measure the liquid’s volume.

What are these three devices?

(100mL) Graduated Cylinder, Volumetric pipette, and Buret

How much of this liquid are you supposed to measure out with a graduated cylinder:

slightly more than 10mL

How much of this liquid are you supposed to measure out with a volumetric pipet:

precisely 10mL

How much of this liquid are you supposed to measure out with a buret:

slightly more than 10mL

In Part B you will determine the density of a solution.

This solution is

degassed soda

A 50-mL buret is used in Part B. How must you prepare the buret before filling it with the solution?

Prepare the buret by first rinsing it with distilled water, then rinsing it with a small quantity of the de-gassed soda, as demonstrated by the instructor.

Note: To rinse with soda, close the stopcock and add about 10 mL of soda to the buret using a funnel. Turn the

buret horizontally and roll (rotate) it so that the soda has contact with all the inside surfaces. Then open the

stopcock and let the soda drain out of the tip.

After filling the buret, you will use it to deliver small amounts of the solution into a container.

a. What is this container?

a 50mL Erlenmeyer flask

In Part C you will determine the density of a solid.

This solid is

an unknown solid

Objectives of this laboratory are

(A) To determine the density of distilled water using different types of volumetric glassware in order to compare the precision of this glassware.

• (B) To determine the density of a de-gassed soda via graphical analysis.

• (C)To determine the density of an unknown metal using the technique of water displacement,and use this value to identify the metal.

• To use Microsoft Excel© to perform graphical and statistical analyses of the experimental data obtained.

Density is a

physical property, and intensive property

physical property

characteristics of

a substance that can be observed or measured without changing its chemical identity. Other

physical properties include melting point and solubility.

intensive property

is one that does not

depend of the amount of matter present. In other words, a substance will have the same

density whether its quantity is large or its quantity is small.

extensive property

is

one that does depend on the amount of matter present.

Density

M/V

S.I. unit of density

kg/m³ (in chemistry often expressed in units of g/cm³)

standard deviation

indicates the degree to which a set of measurements deviate from the average value

What defines a outlier?

when a number is either more than 2 standard deviations from the mean

More scatter and higher standard deviation

less precise

less scatter and lower standard deviation

more precise

How precisely is the graduated cylinder measured?

0.1mL or one decimal place

How precisely is the volumetric pipet measured?

0.01mL

How precisely is the Buret measured?

0.01mL