CH 102 Prelab 2

The following items deal with safety issues in the Flame Test experiment. Check all the boxes that contain correct answers to each question.
(a) In the flame test experiment, you will be working with two types of hazard. Which are they? (Select all that apply.)

hydrochloric acid, corrosive solution
open flame

(b) When working with a Bunsen burner, which of the following precautions must be observed? (Select all that apply.)

Flammable liquids should never be heated with a Bunsen burner.
If the flame blows out, the gas must be turned off, because gas could accumulate and an explosion could occur.
The burner must never be left unattended.
The area near the burner should be clear of paper and other flammables.
The substance being heated should never be pointed at people.
The area above the burner must be clear before it is lit.

(c) If one spills hydrochloric acid on one's hands, what is the FIRST thing one should do?

Rinse them in running water.

What should be done with the wastes in the Flame Test experiment?

They should be flushed down the sink with plenty of water.

The following questions deal with using a Bunsen burner. Choose the response that best answers each question.
(a) What is the hottest part of a Bunsen burner flame?

the tip of the inner, dark blue cone

(b) The valve on the bottom of the burner controls which of the following?

the gas flow

(c) Twisting the sleeve to open the holes (baffles) above the base of the burner does which of the following?

allows more air (oxygen) into the flame

(d) When cleaning the wire between flame tests, most of the cleaning is accomplished when?

while rinsing the wire with acid

In the flame test, a solution containing an ionic compound is heated. An observation is made concerning the color of the heated solution.
(a) Color in a substance arises from which two closely related processes?

absorption and emission

(b) What process is occurring when the solution is heated?

An electron absorbs energy and it makes a transition to a higher energy orbital.

(c) What process is occurring when the color appears in the flame?

An electron emits energy and it makes a transition to a lower energy orbital.

The following questions deal with the nature of light and color. (Enter your answers using scientific notation.)
(a) A photon has a wavelength of 630. nanometers (nm). What is the length in meters?

6.3e-7

(b) What is the frequency of this photon?

4.8e14

(c) What is the energy of this photon?

3.2e-19

The following questions deal with the mathematical relationships between quantities involved in light and energy. Choose the response that best answers each question.
(a) Match the symbol with the property it represents.

v: frequency
𝜆: wavelength
c: speed of light

(b) Which two quantities are inversely proportional to one another?

frequency and wavelength

(c) Which of the following is a true statement?

390 nm blue light is higher in energy than 610 nm yellow light.

When ionic solids dissolve in water, they produce soluble aqueous cations and anions. For example, adding MgBr2 solids to water will produce ions according to the dissolution reaction below.
MgBr2(s) → Mg2+(aq) + 2 Br−(aq)
cation anion
In this lab, you will be observing the color of emission from ions dissolved in solution. Please write the dissolution reaction for each of the ionic solids below. (Use the lowest possible coefficients. Include states-of-matter under the given conditions in your answer.)
(a) KNO_3
(b) BaCl2
(c) Ba(NO3)2

a) KNO_3(s) → K^1+(aq)+NO_3^1- (aq)
b) BaCl_2(s) → Ba^2+(aq)+2Cl^1-(aq)
c) Ba(NO_3)_2(s)-->Ba^2+(aq)+2NO_3^1-(aq)