10/27 in-class activity

1. Fill in the table:

Symbol	#Protons	#Neutrons	#Electrons	Charge
­­­­3216S2-	16	16	18	-2
13756Ba2+	56	81	54	+2
3717 Cl-	17	20	18	-1
5224Cr7+	24	28	17	+7

2. Name the family to which each of the following elements belong:

a.) Transition metal b.) Noble Gas c.) Alkaline earth metal  d.) Alkali metal 
e.) Actinides   f.) Lanthanides  g.) Halogens

3. Fill in the table:

NH4Cl	ammonium chloride
MgSO4	magnesium sulfate
UF4	uranium (IV) fluoride
NaCN	sodium cyanide
FeCl3	iron (III) chloride
RbNO3	rubidium nitrate
(NH4)2Cr2O7	ammonium dichromate
HBr	hydrobromic acid

4. An unknown sample of mystery element “T” is injected into the mass spectrometer.  According to the mass spectrum, 7.42% of the element is present as ⁶T, and 92.58% is present as ⁷T.  The mass values are 6.02 amu and 7.02 amu, respectively.  Calculate the average atomic mass and identify the mystery element.

The average atomic mass is 6.95 amu.  The element is Lithium.

5. How many moles of each element are present of 1.0 mol Ba₃(AsO₄)₂ (barium aresenate)?

3.0 mol Ba, 2.0 mol As, 8.0 mol O

6. Balance the following equation:

2 Fe(s) + 6 HC₂H₃O₂(aq) à 2 Fe(C₂H₃O₂)₃ (aq) + 3 H₂(g)

7. How many grams of water vapor can be generated from the combustion of 18.74 g ethanol?

21.99 g

8. Balance the following redox reaction in acid solution.  What is the reducing agent?  What is the oxidizing agent?

H₃AsO₄ + 4 Zn + 8 H⁺ à AsH₃ + 4 Zn²⁺ + 4 H₂O

As is reduced: it is the oxidizing agent.

Zn is oxidized: it is the reducing agent.

9. Balance the following redox reaction in basic solution.  What is the reducing agent?  What is the oxidizing agent?

HXeO₄^- + 3 Pb + 2 OH^- à Xe + 3 HPbO₂^-

Pb is oxidized: it is the reducing agent.

Xe is reduced: it is the oxidizing agent.

 Original Worksheet:

1. Fill in the table:

Symbol	#Protons	#Neutrons	#Electrons	Charge
­­­­3216S2-
	56	81	54
____ Cl-		20
5224____7+

2. Name the family to which each of the following elements belong:

a.) Rh b.) Xe  c.) Ca   d.) Rb  e.) Pu  f.) Dy   g.) I

3. Fill in the table:

NH4Cl
	magnesium sulfate
UF4
NaCN
	iron (III) chloride
RbNO3
	ammonium dichromate
	hydrobromic acid

4. An unknown sample of mystery element “T” is injected into the mass spectrometer.  According to the mass spectrum, 7.42% of the element is present as ⁶T, and 92.58% is present as ⁷T.  The mass values are 6.02 amu and 7.02 amu, respectively.  Calculate the average atomic mass and identify the mystery element.

5. How many moles of each element are present of 1.0 mol Ba₃(AsO₄)₂ (barium aresenate)?

6. Balance the following equation:

___Fe(s) + ___HC₂H₃O₂(aq) à ___Fe(C₂H₃O₂)₃ (aq) + ___H₂(g)

7. How many grams of water vapor can be generated from the combustion of 18.74 g ethanol?

8. Balance the following redox reaction in acid solution.  What is the reducing agent?  What is the oxidizing agent?

H₃AsO₄ + Zn à AsH₃ + Zn²⁺

9. Balance the following redox reaction in basic solution.  What is the reducing agent?  What is the oxidizing agent?

HXeO₄^- + Pb à Xe + HPbO₂^-

10/20 in-class activity

25.00 mL of 5.2159 M sulfuric acid (aq) is mixed with 25.00 mL 3.9009 M barium hydroxide (aq).

1. Write the balanced chemical equation.  What is the precipitate?

H₂SO₄ (aq) + Ba(OH)₂ (aq) à BaSO₄ (s) + 2 H₂O (l)

Barium sulfate is the precipitate.

2.  What is the limiting reactant?

Determine number of moles of reactants:

5.2159 M H₂SO₄ * 0.02500 L = 0.1304 mol H₂SO₄

3.9009 M Ba(OH)₂ * 0.02500 L = 0.09752 mol Ba(OH)₂

There is more H₂SO₄ than Ba(OH)₂.  Since they react in a 1:1 ratio, Ba(OH)₂ is therefore the limiting reactant.

3. How much precipitate is formed (in g)?  What is the mass of excess reagent?

All of the Ba(OH)₂ will be used up.  Since molar ratio for Ba(OH)₂ and BaSO₄ is 1:1, the moles of BaSO₄ product will be 0.09752 mol.  Multiply by the molar mass of barium sulfate.

0.09752 mol BaSO₄ * 233.3984 g/1 mol = 22.76 g BaSO₄ (s)

0.09752 mol of H₂SO₄ will react with the same number of moles of barium hydroxide.  Originally, there was 0.1304 mol H₂SO₄.   Multiply the remaining number of moles by the molar mass of sulfuric acid.

0.1304 mol H₂SO₄ – 0.09752 mol H₂SO₄ = 0.03288 mol H₂SO₄

0.03288 mol H₂SO₄ * 98.0842 g/1 mol = 3.225 g H₂SO₄ (aq)

4. If you weigh 18.24 g precipitate, what was the percent yield?

% yield = actual yield / theoretical yield = 18.24 g/22.76 g = 80.14%

10/13 In-class activity

10/6 Practice Problems

Please review these practice questions.  These problems are good practice for both ALECS and exams.

10/6 Class Activity

Naming Simple Compounds

Use Section 2.9, tables 2.3 - 2.8, and the flow chapters in that section to complete the following problems. (Remember: the exam will NOT be open book, so you will need to memorize the procedures for naming compounds.)

1.      Name the following compounds:

a.)    PbI₂

b.)    NH₄Cl

c.)    Fe₂O₃

d.)   Cr(OH)₃

e.)    K₂Cr₂O₇

f.)     KH₂PO₄

g.)    NaHSO₄

h.)    NaHSO₃

2.      Write the formulas for the following compounds:

a.)    Nitrogen triiodide

b.)    Phosphorous pentachloride

c.)    Carbon monoxide

d.)   Sulfuric acid

e.)    Sulfate ion

f.)     Dinitrogen tetroxide

g.)    Ammonia

h.)    Ammonium

i.)      Molecular nitrogen

j.)      Persulfuric acid

k.)    Persulfate ion

l.)      Silver chloride

m.)  Silver nitrate

n.)    Manganese (IV) oxide

o.)    Sulfurous acid

p.)    Sulfite ion

q.)    Hyposulfurous acid

r.)     Hyposulfite

Answers:

1.      a.) lead (II) iodide  b.) ammonium chloride  c.) iron (III) oxide  d.) chromium (III) hydroxide  e.) potassium dichromate  f.) potassium dihydrogen phosphate  g.) sodium hydrogen sulfate or (more commonly) sodium bisulfate  h.) sodium bisulfite

2.      a.) NI₃  b.) PCl₅  c.) CO  d.) H₂SO₄  e.) SO₄^2-  f.) N₂O₄  g.) NH₃  h.) NH₄⁺  i.) N₂  j.) H₂SO₅  k.) SO₅^2-  l.) AgCl  m.) AgNO₃  n.) MnO₂  o.) H₂SO₃  p.) SO₃^2-  q.) H₂SO₂  r.) SO₂^2-

More sig fig practice

1. How many significant figures are in each of the following numbers?

a.) 5.40

b.) 3.97 x 10^-5

c.) 30000

d.) 250.

e.) 1.4895

f.) 1.400

g.) 235.40


2. Complete the following calculations to the appropriate number of sig. figs.:

a.) 234.52 + 25.2 =

b.) 1420 x 320. =

c.) (6.274 x 10^3) x (1.56 x 10^-2) =

d.) 529 ÷ 1.30 =

e.) 430. - 44.67 =

f.) (1.343 x 10^2) + (1.5654 x 10^2) =

Answers:
1. a.) 3  b.) 3  c.) 1  d.) 3  e.) 3  f.) 4  g.)  5
2. a.) 259.7  b.) 454,000  c.) 97.9  d.) 407  e.) 385  f.) 290.8 or 2.908 x 10^2

Bunsen burner video

This video will show you how to light and adjust a Bunsen burner.  You will need to use these skills in your first lab - please come prepared.

http://www.youtube.com/watch?v=9QpIcX-xw1Q