Download CHAPTER 1 Chemical Foundations

CHAPTER 1 Chemical Foundations
Difference between an element, a compound, and a molecule
Subscripts vs. coefficients
Temperature conversion
K = °C + 273.15
1. What is absolute zero in degrees Celcius?
Density
Measured in g/cm3 or g/mL
2. A cube of ruthenium metal 1.5 cm on each side has a mass of 42.0 g. Will this sample float on
water?
State of Matter - Solid (s) Liquid (l) Gas (g)
Interparticle distance
Definite Volume/ Definite Shape
Physical vs chemical change
Evidence of chemical change
Classification of Matter
Pure
Mixture
Separating mixtures
Miscible vs. immiscible

Filtration
 Distillation
volatile = ease of vaporizing
 Chromatography
Many kinds! Paper, gas, column
CHAPTER 2 Atoms, molecules & Ions
Law of conservation of mass
Mass is neither created nor destroyed
Law of definite proportion
A given compound always contains the same proportions of elements by mass
(H2O is always 1/9 H and 8/9 O by mass)
Law of multiple proportions
When two elements form a series of compounds, the ratios of the masses of one element that
combine with a fixed mass of the other can always be reduced to small whole numbers
(100 g of C reacts with 133g O or 266g O, ratio of 266:133 = 2:1, so 2 forms of C + O are CO & CO2)
3. How does balancing a reaction show conservation of mass?
4. A sample of H2SO4 contains 2.02g of hydrogen, 32.07g of sulfur and 64.00g of oxygen. How
many grams of sulfur and grams of oxygen are present on a second sample of H2SO4 containing
7.27g of hydrogen?
5. Hydrazine, ammonia and hydrogen azide all contain only nitrogen and hydrogen. The mass of
hydrogen that combines with 1.00 gram of nitrogen for each compound is 1.44 x 10 -1g, 2.16 x
10-1g, and 2.40 a 10-2g respectively. Show these data illustrate the law of multiple proportions.
History
 Evolving model that is updated according to evidence
Dalton
Thompson
Milikan
Becquerel
Rutherford
Bohr
Atomic Structure
3 subatomic particles, mass, location, charge
Counting p, n, e
Cation/anion
Atomic number
Isotopes
Avg atomic mass (chapter 3)
6. A sample of natural copper is analyzed and determined to contain 69.09% Cu-63 and 30.91%
Cu-65.
a) Before calculating the exact average atomic mass, would you expect it to be 64.00?
Why or why not?
b) Calculate the average atomic mass of
the sample
Mass spectrometer (chapter 3)
7. According to the mass spectrum graph of Atom
Y, which of the following statements is false?
a) Peaks A and D come from atoms that have the
same number of electrons
b) There are 7 isotopes of atom Y
c) Peak C comes from the most abundant isotope
d) Peak D comes from an atom with 4 more
protons than the atom that gave peak B
8. Which peak comes from the atom with the
greatest number of neutrons?
Periodic Table
Group vs period
Metals/nonmetals/metalloids
location
properties
Group names 1, 2, 3-12, 17, 18
9. Identify the elements that correspond to the following atomic numbers. Label the group it
belongs to.
a) 17
b) 4
c) 26
d) 19
e) 2
f) 14
Allotropes
Different structure -> different properties
Hydrates
CuSO4•5H2O
10. Name Cr(NO3)3· 6H2O. What percent is water?
11. Write the formula for Calcium chloride dihydrate.
12. A 20 gram sample of a hydrated compound is placed into crucible and heated. The data for this
laboratory investigation is shown below.
Mass of crucible
15.5867 g
Mass of crucible and hydrated sample 19.7644 g
Mass of crucible and hydrated sample 18.4388 g
after 1st heating
Mass of crucible and hydrated sample 18.0244 g
after 2nd heating
Mass of crucible and hydrated sample 18.0242 g
after 3rd heating
a) How can we conclude all of the water of hydration has been removed?
b) What is the percent water in the hydrated sample?
CHAPTER 3 Stoichiometry
Percent composition
13. Calculate the percentage of carbon in ethane (C2H6)
14. Calculate the percentage of oxygen in water
Mole concept
What is a mole?
15. How many hydrogen atoms in 0.350 mol of water?
Conversions mass ↔mole
16. How many grams in 0.350 mol of water?
17. Calculate the number of moles of sulfur dioxide in 130 g.
18. Calculate the mass in grams of .6 moles of calcium nitrate.
Molecular v empirical formulas
Identify
Convert
19. The empirical formula for ascorbic acid was C3H4O3. It’s molecular weight is 176. What is the
molecular formula?
Determine empirical formula from analyses
% to mass, mass to mole, divide by small, times ’til whole.
20. The compound para-aminobenzoic acid (you may have seen it listed as PABA on your bottle of
sunscreen) is composed of carbon (61.31%), hydrogen (5.14%), nitrogen (10.21%), and oxygen
(23.33%). Find the empirical formula of PABA.
21. Ascorbic acid, vitamin C, contains 40.92% C, 4.58% H, and 54.50% O. What is the empirical
formula for ascorbic acid?
Combustion Analysis
Compounds containing C, H and O are routinely analyzed through combustion in a chamber like this.
– C is determined from the mass of CO2 produced.
– H is determined from the mass of H2O produced.
– O is determined by difference after the C and H have been determined.
22. A 0.255g sample of isopropyl alcohol was burned in a combustion train and 0.561g CO2 and
0.306g H2O were formed. Determine the empirical formula of ascorbic acid.
Hints….
(Calculate the moles of Carbon and Hydrogen in the compound.)
(Calculate the moles of Oxygen in the compound.)
(The mole ratios are the subscripts of the empirical formula. (divide by small, times ’til whole)
23. A sample of a common alcohol with a mass of 4.599 g, containing C, H and O, was combusted in
excess oxygen to yield 8.802 g of CO2 and 5.394 g of H2O.
The alcohol contains only carbon, hydrogen, and oxygen. What is the empirical formula of the
alcohol?
24. The combustion of 62.63 grams of a compound which contains only C,H and O yields 134.43
grams of CO2 and 13.75 grams of H2O.
a) What is the empirical formula of the compound?
b) If the compound’s molecular weight is 156 g/mol, determine the molecular formula.
Reactions
Product/reactant
Balancing
You can only change the coefficients to balance (never subscripts)
You can only use whole numbers to balance
25. Balance the following equations:
__Ca + __H2O → __H2 + __ Ca(OH)2
__ Cu + __ O2 → __ CuO
__ Na + __ O2 → __ Na2O
__ Fe + __ HCl → __ FeCl2 + __ H2
__ Fe + __ Br2 → __ FeBr3
__ C4H8 + __ O2 → __ CO2 + __ H2O
Types
Combustion (complete/incomplete)
CH4 (g) + 2 O2 (g)  CO2 (g) + 2 H2O (g)
Combination (synthesis)
2 Mg (s) + O2 (g)  2 MgO (s)
Decomposition
2 KClO3 (s)  2 KCl (s) + O2 (g)
Writing reactions
26. The combination reaction that occurs between lithium metal and fluorine gas.
27. The reaction that occurs when solid sodium azide (NaN3) decomposes rapidly into it’s
constituent elements as an airbag is inflated.
28. Si2H6 burns when exposed to air
Stoichiometry
Mass of reactant  moles of reactant  moles of product  mass of product
Dimensional analysis
29. a) Balance this equation showing the burning of methane below, to answer the following
questions.
__ CH4 + __ O2 → __ CO2 + __ H2O
b) How many grams of oxygen are required to produce 2.23 g of carbon dioxide?
c) How many grams of water will be produced when 34.0 g of methane is burned?
30. Baking soda (NaHCO3) is often used as an antacid. It neutralizes excess hydrochloric acid
secreted by the stomach according to the following:
NaHCO3 (s) + HCl (aq)  NaCl (aq) + H2O (l) + CO2 (g)
Milk of magnesia, which is an aqueous suspension of magnesium hydroxide, is also used as an
antacid.
Mg(OH)2 (s) + 2 HCl (aq)  MgCl2 (aq) + 2H2O (l)
Which is more effective as an antacid per gram NaHCO3 or Mg(OH)2?
Limiting reactants
31.
H2(g) + O2(g) → H2O(l)
a) Calculate the stoichiometric ratio of moles H2 to moles O2
b) Calculate the moles of water created when 1.50 mol H2 is mixed with 1.00 mol O2
c) Determine the limiting reactant (H2 or O2) for the mixture in (b)
32. For the reaction: Na2O + H2O → NaOH
a) What weight of NaOH could be made from 12.4 g of Na2O and 42.1 g of H2O?
b) What would be the limiting reagent if 100 g each of Na2O and H2O were allowed to react?
Percent yield
33. Methanol (CH3OH), also called methyl alcohol, can be used as a fuel in race cars and is a potential
replacement for gasoline. Methanol can be manufactured by combining gaseous carbon monoxide and
hydrogen. Suppose 68.5kg CO (g) is reacted with 8.60 kg H2 (g).
a) Calculate the theoretical yield of methanol
b) If 3.57 x 104g CH3OH is actually produced, what is the percent yield of methanol?