Download Element of the Day

Element of the Day
Ba
Barium is a chemical element with symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Because of its high chemical reactivity barium is never found in nature as a free element. The most common naturally occurring minerals of barium are barite (barium sulfate, BaSO4) and witherite (barium carbonate, BaCO3), both being insoluble in water. Barium's name originates from the alchemical derivative "baryta", which itself comes from Greek βαρύς (barys), meaning "heavy." Barium was identified as a new element in 1774, but not reduced to a metal until 1808, shortly after electrolytic isolation techniques became available.
Which of the following are soluble: Ba(OH)2, Ba(NO3)2, BaS
1
Chemistry
1. Element of the Day ­5
2. Review Lab Investigation ­15
3. Quiz ­20
4. Demonstration ­10
5. Redox Notes ­20
6. Start Homework ­10
Announcements
Due Today: Lab Investigation
Due Monday, February 24: Read pages to 188 to 199 in chemistry textbook.
2
Review Lab Investigation
3
Review Notes
Reactions in Aqueous Solutions
Solubility Rules ­ Write with at least 2 different colors!
1. Nitrate (NO31­) salts are soluble.
2. Salts of Na+, K+, and NH4+ are soluble.
3. Chloride, Bromide, and Iodide salts are soluble, except
those with Ag1+, Hg2+, or Pb2+.
4. Sulfate salts (SO42­) are soluble, except those with Ba2+, Pb2+, and Ca2+.
5. Most Sulfide (S2­), carbonate (CO32­), and phosphate (PO43­) are insoluble.
6. Hydroxide (OH­) compounds are insoluble, except those with Na1+, K1+, Ca2+, or Ba2+.
4
5
Quiz
6
7
Demonstration
The yellow–blue oscillating reaction is known as the Briggs­Rauscher reaction. The color changes observed during the reaction are due to oscillations in the concentration of iodine (I2) and iodide ions (I–). The yellow color is attributed to an increase in the I2 concentration. The dark blue color arises from the formation of a starch–iodine complex as both the I– and I2 concentrations increase. The colorless solution is caused by the decline in I2 concentration and the continued rise in I– concentration. The dark blue starch–iodine complex consists of amylose–iodine (see Figure 1). The color of the complex, blue­black, comes from the pentaiodide anion, I5– formed when the I2 and I– concentrations are elevated. Though normally an unstable anion, I5– becomes stable as a part of the starch complex as both the I– and I2 concentrations increase. The overall Briggs–Rauscher reaction is:
IO3–(aq) + 2H2O2(aq) + CH2(CO2H)2(aq) + H+(aq) → ICH(CO2H)2(aq) + 2O2(aq) + 3H2O(l)
The overall reaction may be broken down into two component reactions in which an intermediate compound HOI is generated and then consumed.
Equation 1: IO3–(aq) + 2H2O2(aq) + H+(aq) → HOI(aq) + 2O2(g) + 2H2O(l) Equation 2: HOI(aq) + CH2(CO2H)2(aq) → ICH(CO2H)2(aq) + H2O(l) 8
Oxidation Reduction Reactions
Oxidation Reduction: is a reaction that involves the transfer of an electrons. The transfer of electrons can be a ______________ of chemical reactions. This transfer of electrons occurs when a _________ and a _________ react forming a _____________. This transfer can also happen when two nonmetal react; however, this compound is not _____________.
Example: Thermite Reaction 2Al(s) + Fe2O3(s) ­­> 2Fe(s) + Al2O3(s)
Picture
OILRIG = Oxidation is _________ Reduction is ___________
For problems 1 and 2 below:
1. Draw a picture and show transfer of electrons
2. Identify which species is oxidized and which is reduced.
Problem 1: 2Al(s) + 3I2(s) ­­> 2AlI3(s)
Problem 2: 2Na(s) + Br2(l) ­­> 2NaBr(s)
9
Classifying Reactions Graphic Organizer
10
Redox Video
11
Exit Question:
What two events occur in a redox reaction?
Reminder(s):
Due Today: Lab Investigation
Due Monday, February 24: Read pages to 188 to 199 in chemistry textbook.
12