Download FE Review Chemistry - UTSA College of Engineering

FE Review Chemistry
Heather J. Shipley
Assistant Professor
Civil and Environmental Engineering
UTSA
Basic Concepts
Nucleus of atom
Proton: positively charged particle, 1.00728 amu
Neutron: neutral particle, 1.00866 amu
Electron: negatively charged particle, 0.0005486 amu
neutron
proton
electron
Definitions
• Atomic mass: the total mass of protons,
neutrons, and electrons in a single atom
• Atomic number: the number of protons in
the nucleus
• Element: a substance only composed of
one type of atom
• Isotope: element with the same number of
protons but different atomic masses
Electron Configuration
Periodic Trends
Electronegativity
Ionization Energy
Atomic Radius
• Electronegativity: is a chemical property
that describes the tendency of an atom or
a functional group to attract electrons (or
electron density) towards itself.
• Ionization energy: is the energy required to
remove electrons from atoms or ions.
• Atomic radius: the size of the atom
Molecular Bonding
E.g. CaCl2 = 40.08+2(35.45) = 110.97 g/mole
Elements combine to form molecules in order to fill their shells. Usually an element
has 8 electrons around it, except H which is 2 and B which is 6
Formed by sharing a pair of electrons
formed by electrostatic attraction
between positive and negative ions
Gas Laws
• Ideal Gas law
– PV= nRT
• No intermolecular forces
• Gas molecules occupy no specific volume
• Standard Temperature and Pressure
– 0C and 1atm
– 22.4L/mole
Gas Laws cont.
– P = Pa +Pb +Pc+…
• Henry’s Law: relates gases and solutions
– KH=Pgas/C = partial pressure of a gas (atm)/
concentration in solution (M)
Solution Chemistry
Solution Chemistry
Equilibrium
aA + bB = cC +dD
• K = [C]c[D]d/ [A]a[B]b = products/reactants
pH
• Water dissociates into H+ and OH– H2O = H+ + OH-
• Equilibrium
– Kw = [H+][OH-]/[H2O] = [H+][OH-]
• Kw = 1x10-14
• pH = log(1/[H+])
– pH >7: alkaline ([OH-]>[H+])
– pH < 7: acidic ([OH-]<[H+])
• pOH = log(1/[OH-])
• pH+pOH = 14
Example
• Calculate the pH of 10g/L NaOH solution
– [NaOH] = 10g/L*1mol/40g = 0.25M
– [OH-] = 0.25M * 1mol OH/1mol NaOH = 0.25M
– pOH = log(1/0.25) = 0.602
– pH = 14-0.602 = 13.398
Chemical reactions
• In chemical reactions elements or molecules
rearrange themselves to form more stable
molecules. The reaction is highly favored if
electrons are transferred from an element which
loosely binds electrons to an element that tightly
binds electrons. The element which donates the
electrons is the reducing agent and the element
which receives is the oxidizing agent.
Reactions
• Precipitation/Dissolution Reactions
– Dissolved ions react with other ions to form insoluble compounds
– AaBb (s) = aAb+ + bBa– Ksp = [A]a[B]b
• Undersaturated if [A]a[B]b < Ksp
• Saturated if [A]a[B]b = Ksp
• Super-saturated if [A]a[B]b > Ksp
• Acid/Base reactions
– Substances that influence pH, see earlier slides
• Complexation Reaction
– Occurs when 2 or more atoms, molecules, or ions combine and
form a stable product
• E.g. Fe(H2O)62+
Reactions
• Oxidation and Reduction Reactions (Redox)
– Involves transfer of e-; one compound gives up e- the other
takes them up
– Compound giving up e- is being oxidized, so reducing agent
– Compound accepting e- is being reduced, oxidizing agent
• Ex. Corrosion of Fe
– Fe0 = Fe2+ +2e– 2H+ + 2e- = H2 (g)
– Overall Fe0 + 2H+= Fe2+ +H2 (g)
• Combustion Reaction: burning of fuel with
oxygen
Electrochemical cells
Balancing Equations
• 2 rules
– Mass must be conserved
• The number of atoms of an element on the left
hand side of the rxn needs to equal the amount on
the right
• The atoms can change what they associate with
but not be created or destroyed
– Charge must be conserved
• charge on the left must equal the charge on the
right
Example
Balance the equation?
• SO42- + H+ + CH2O  HS- + CO2 + H2O
• 1SO42- + 1H+ + 2CH2O  1HS- + 2CO2 +
2H2O
Kinetics
• Speed of a reaction
• Zero order: rxn proceeds at a rate independent of the
conc. of any reactant
– C-C0 = -kt
• First Order: rxn proceeds at a rate directly proportional to
the concentration of one reactant
– C = C0e-kt
– Half life
• t1/2 = ln2 / k
• Second order: proceeds at a rate proportional to the
square of the conc. of 1 reactant or the product of 2
reactants
– 1/C-1/C0 = kt
Organic Chemistry
• Alkanes
Organic Chemistry
Practice problems FE Exam: Chemistry
1. Which statement is incorrect?
a) solutions may be homogeneous or heterogeneous
b) matter may be homogeneous or heterogeneous
c) Both elements and compounds are composed of atoms
d) All substances contain atoms
e) substances are always homogeneous
2. Which statement is incorrect?
a) An element may be separated into atoms
b) An element may be a gas, a liquid, or a solid
c) A compound can be separated into its elements by chemical means
d) An element is always heterogeneous
e) A compound may be a gas, a liquid, or a solid
3. In relation to the proton, the electron is
a) about the same mass and of opposite charge
b) about the same mass and of the same charge
c) about the same mass and with no charge
d) much lighter and of opposite charge
e) much heavier and with no charge
4. A negative ion of a certain element can be formed by
a) subtraction of a proton from and atom of that element
b) subtraction of a electron from and atom of that element
c) subtraction of a neutron from and atom of that element
d) addition of a electron from and atom of that element
e) addition of a neutron from and atom of that element
5. Metallic conduction involves
a) migration of cations towards a positively charged electrode
b) migration of cations towards a negatively charged electrode
c) passage of electrons from one atom of a metal to another
d) migration of anion towards a negatively charged electrode
6. Which of the following statement is true?
a) within a group of elements in the periodic table, the largest atom has the
highest ionization potential
b) within a period of elements in the periodic table, the noble gas has the highest
ionization potential
c) when all valence p orbitals of an atom are half filled the ionization potential of
that atom is lower than the ionization potential of an atom with only 2 electrons in
valence p
d) it is easier to form a 2+ ion than a 1+ ion
e) ionization potential is the same as Electronegativity
7. Which one of the following elements has the largest atomic radius?
a) Li
b) Na
c) Be
d) Mg
e) P
8. In the series of elements B, Al, Ga, In
a) Electronegativity increases from B to In
b) metallic character increases from B to In
c) ionization energy increases from B to In
d) nonmetallic character increases from B to In
e) none of the above
9. Which of the following lists contains only nonmetals?
a) Be, H, Os
b) Ge, Pd, Si
c) C, S, F
d) Ca, Cl, B
e)Zn, Ga, Ge
10. In an element
a) the atomic number is equal to the number of neutrons in the atom
b) the number of protons always equals the number of neutrons in the atom
c) the mass number is equal to the number of electrons in the atom
d) the atomic number is equal to the number of protons in the atom
e) the number of electrons can never equal the number of neutrons in the atom
11. What is the ground state electron configuration of Al, Z = 13
a) 1s22s22p53s23p1
b) 1s22s22p63s23p1
c) 1s22s22p63s24s1
d) 1s22s22p63s23p2
e) 1s22s22p63s23d1
12. Which of these electron configurations is found in periodic Group VI
a) ns2
b) np6
c) ns4
d) ns2np4
e) ns4np-1
13. From a consideration of electron configuration which of the following elements
would you expect to be most similar in chemical properties to Sr
a) Rb
b) Y
c) Sc
d) Ba
14. How many electrons does a phosphorus atom have in its set of valence shell p orbitals
a) 0
b) 1
c) 2
d) 3
e) 10
15. An atom of an unknown element Q as a mass number of 31 and the nucleus contains
15 protons. The element is
a) Ga
b) S
c) P
d) Pd
e) Sc
16. An ion of an unknown element has an atomic number of 15 and contains 18 electrons.
The ion is
a) P3b) Ar
c) O2d) Si3e) S+
18. What one of the following compounds is classified as an alkane?
a) ethylene
b) benzene
c) propane
d) acetylene
e) ethanol
19. Which one of the following bonds is most covalent?
a) MgCl
b) AlP
c) NaCl
d) MgS
e) NaP
20. The sum of the oxidation states of all the atoms in a neutral molecule
a) must be a small positive number
b) must be a small negative number
c) must be zero
d) can be either positive or negative, but not zero
e) can have any value, including zero
21. The oxidation state of sulfur (S) in the ion SO32- is
a) 1+
b) 2+
c) 3+
d) 4+
e) 623. An empty Al Coke can weighs 50g. How many moles of Al does one Coke can
contain?
a) 1350
b)1.85
c) 1.0x1025
d) 27
24. A 27g sample of OF2 contains how many molecules?
a) 3.0x1023
b) 2 times 6.0x1023
c) 12.0x1023
25. How many grams are there in 0.01mole of Na2SO4?
a) 7.1g
b) 14.2g
c) 9.6g
d) 1.42g
e) 0.71g
26.What is the volume at standard temperature and pressure of 16g of gaseous SO2?
a) 22.4L
b) 11.2L
c) 5.6L
d) 16.8L
e) 64L
27. What is the percentage by weight of Al in Al2O3 ?
a) 63
b) 37
c) 23
d) 53
29. What is the expression for the equilibrium constant for the following systems?
2NOCl = 2NO + Cl2
a) K = [NO]2[Cl2]/[NOCl]2
b) K = 2[NO][Cl2]/2[NOCl]
c) K = [NO]2[Cl2]2/[NOCl]2
d) K = [NO]2[Cl2]2/[NOCl]2
30. For the reaction of solid BaO with CO2 according to the equation BaO(s) + CO2(g) =
BaCO3(s), the equilibrium expression is expressed
a) [BaCO3]/[BaO]
b) 1/[CO2]
c) [BaO][CO2]/[BaCO3]
d) [BaCO3]/[BaO][CO2]
31. Assume excess oxygen reacts with methane to form 14g of carbon monoxide
according to the equation 2CH4+3O2 = 2CO+4H2O. How many moles of the methane
will be consumed?
a) 2.0 moles methane
b) one third mole methane
c) 0.25 mole methane
d) 0.5 mole methane
e) 4.0 moles of methane
32. What coefficient is required for NO2 in order to balance the equation?
2Pb(NO3)2 = 2PbO + NO2+ O2
a) 0.5
b) 1
c) 1.5
d) 4
33. What coefficient is required for H2O in order to balance the equation?
Be3N2 + H2O = 3Be(OH)2 + 2NH3
a) 1
b) 2
c) 3
d) 6
34. In the following reaction determine the change if any that occurs in the oxidation
number of the underlined element and the whether the element is oxidized, reduced, or
unchanged.
3Mg + N2 = Mg3N2
a) from 0 to +3, oxidized
b) from 0 to -3, oxidized
c) from +3 to +5, oxidized
d) from 0 to -3; reduced
35. According to the equation 2Al + 6HCl = 2AlCl3 + 3H2
a) production of 1 mole of H2 requires 3 mole of HCl
b) production of 1 mole of AlCl3 requires 3 moles of HCl
c) production of 2 moles of H2 requires 2 moles of HCl
d) production of 2 moles of H2 requires 5 moles of HCl
38. The rate of most chemical reactions increase as the temperature increases primarily
because at higher temperatures
a) the ionic charge is higher
b) the pressure is higher
c) there are increases in the average distances between atoms within molecules
d) there are more collisions involving molecules with sufficient energy for
reaction
39. In electrolysis, the anions migrate to the anode. Which of the following ion migrates
to the other electrode?
a) acidic ions
b) basic ions
c) neutral ions
d) zwittweions
e) cations
40. The reaction of 1 mole of As2O3 with carbon will result in the formation of
As2O3 + 3C = 3CO + 2As
a) 1 gram of CO
b) 1 gram of As
c) 28grams of CO
d) 150 grams As
42. Which of the following elements would not be expected to form a positive ion?
a) Li
b) S
c) Mg
d) As
C
D
B
C
C
D
B
A
B