Chemistry Midterm Free Response Review
Part I. Atomic Structure & Subatomic particles
Mg2+
a)
b)
c)
d)
1. Based on the information provided:
The overall charge of this ion is _________.
The number of protons is ___________.
The number of electrons overall is (greater/less) _________ than the number of protons.
If the atomic number for Magnesium is 12, the number of electrons is ___________.
Cl12. Based on the information provided:
a) The overall charge of this ion is _________.
b) The number of protons is ___________.
c) The number of electrons overall is (greater/less) _________ than the number of protons.
d) The number of electrons is ___________.
Sr2+
a)
b)
c)
d)
3. Based on the information provided:
The overall charge of this ion is _________.
The number of protons is ___________.
The number of electrons overall is (greater/less) _________ than the number of protons.
The number of electrons is ___________.
N-3
4. Based on the information provided:
a The overall charge of this ion is _________.
b) The number of protons is ___________.
c) The number of electrons is ___________.
5.
a) Identify the ion that has 18 electrons and a +2 charge. _______
b) Identify the ion that has 36 electrons and a -1 charge. _______
c) Identify the ion that has 18 electrons and a -3 charge. _______
6) There are four naturally occurring isotopes of the element chromium. The relative
50Cr = 4.31%, 52Cr = 83.76%, 53Cr = 9.55%, 54Cr = 2.38%.
abundance of each is:
Calculate the average atomic mass of chromium.
7a) Give the electron configuration for a neutral atom of selenium.
7b) How many unpaired electrons are there in a neutral atom of selenium?
7c) What is the most common ion that selenium would form? Justify your response.
8a) How many electrons are in the highest occupied energy level of a neutral strontium atom?
8b) Give the four quantum numbers for all of the valence electrons in a neutral strontium atom.
9) What is the frequency of light with wavelength 1.0 x 10-8 m? (c = 3.0 x 108 m/s)
10) What is the wavelength of light with a frequency of 1.0 x 10 20 Hz? (c = 3.0 x 108 m/s)
11) What is the energy of a photon of light with frequency 1.0 x 10 12 Hz? (h = 6.6 x 10-34 J-s)
12) Calculate the deBroglie wavelength of a 100-kg particle travelling at 20m/s.
Part II. Periodic Trends
 Fill in each of the following with either:
INCREASES (I)
DECREASES (D)
STAYS THE SAME (S)
I. Across a period, as atomic number increases:
1) The number of principal energy levels __________________.
2) The distance between the valence electrons and the nucleus __________________.
3) The force of attraction between the valence electrons and the nucleus __________________.
4) From left to right the nuclear charge __________________.
5) As atomic number increases, atomic radius overall _____________.
6) As atomic number increases, electronegativity overall ____________.
7) As atomic number increases, ionization energy overall ____________.
II. Down a group or family, as atomic number increases:
8) The number of principal energy levels __________________.
9) The distance between the valence electrons and the nucleus __________________.
10) The force of attraction between the valence electrons and the nucleus __________________.
11) The addition of principal energy levels down a group __________ the distance between the nucleus and the valence
electrons.
12) As atomic number increases, atomic radius overall __________.
13) As atomic number increases, electronegativity overall ____________.
14) As atomic number increases, ionization energy overall ____________.
III. In General:
15) If electronegativity ____________, it is harder for the atom to attract more electrons.
16) If ionization energy ____________, it is harder to remove electrons.
17) If atomic radius increases, the electrical force between an atom’s nucleus and its valence electrons ____________,
18) Which element in the second period has the greatest atomic radius?
19) Tell which atom in each pair has the larger IONIC radius.
a) Al or B
b) S or O
c) Br or Cl
d) Na or Al
e) O or F
20) Indicate which element in each pair has the greater electronegativity.
a) Calcium, gallium
b) Lithium, oxygen
c) Chlorine, sulfur
d) Bromine, arsenic
Part III. Bonding
Complete the following chart.
Molecule / Ion
1) CO2
2) N2
3) HCN
4) SO42-
5) ClO31-
6) SO2
7) CO32-
8) XeF4
9) PCl5
10) SeF4
Lewis Structure
VSEPR numbers
EDG
MG
Part IV. Writing Chemical Formulas & Naming Compounds
Write formulas for these compounds:
1. Potassium sulfide
_____________________
2. Tin (IV) chloride
_____________________
3. Dihydrogen monosulfide
_____________________
4. Calcium oxide
_____________________
5. Aluminum fluoride
_____________________
6. Trinitrogen pentoxide
_____________________
7. Iron (III) carbonate _____________________
8. Sulfur hexafluoride _____________________
9. Ammonium hydroxide
_____________________
10. Magnesium phosphate
_____________________
11. Which of the ten compounds listed above are ionic compounds? (Circle them.)
12. How can you distinguish between an ionic compound and a molecular compound?
calcium
carbon
oxygen
potassium
13. Choose from the elements above to write a formula for an IONIC compound.
__________
14. Name the compound you gave in #13. ________________________________________
15. Choose from the elements above to write a formula for a MOLECULAR compound.
__________
16. Name the compound you gave in #15.________________________________________
Part V. Reactions Practice
For each of the following write a balanced chemical equation.
1.
Write balanced equation for the decomposition of potassium choride into its
elements.
2.
Write balanced equation for the complete combustion of octane, C 8H18.
For each of the following reactions that occur, write a balanced chemical equation. If
it does not occur, write “No Rxn”.
3.
Zn (s) + H2SO4 (aq) 
4.
Na (s) + H2O (l) 
5.
Sn (s) + NaNO3 (aq) 
6.
Cl2 (g) + NaBr (aq) 
7.
Fe (s) + Pb(NO3)2 (aq) 
8.
I2 (g) + NaCl (aq) 
9.
Ca (s) + HCl (aq) 
For each of the following write a balanced chemical equation with phases. All reactants
are dissolved in water.
10. barium chloride + ammonium carbonate 
11. magnesium nitrate + copper(II) sulfate 
12. lead (II) nitrate + potassium carbonate 
13. silver nitrate + sodium phosphate 
Part VI. Stoichiometry
Determine the empirical formula of the following compounds based on percent composition
data:
1. 42.9% C and 57.1 %O
2. 32.00% C, 42.66% O, 18.67% N, and 6.67% H
3. 71.72% Cl, 16.16% O, and 12.12% C
Free Response Answer Key
PAGE 1
Question 1
a. +2
b. 12
c. Less
d. 10
Question 2
a. -1
b. 17
c. Greater
d. 18
Question 3
a. +2
b. 38
c. Less
d. 36
Question 4
a. -3
b. 7
c. 10
Question 5
a. Ca 2+
b. Br c. P 3PAGE 2
Question 6
52.0569 g
Question 7
a. 1s22s22p63s23p64s23d104p4
b. 2
c. Se2- , it forms octet
Question 8
a. 2
b. [5,0,0,+1/2] and [5,0,0,-1/2]
Question 9
3 x 1016 Hz
Question 10
3 x 10-12 m
Question 11
6.6 x 10-22 J
Question 12
3.3 x 10-37 m
PAGE 3
Question I
1) S
2) D
3) I
Page 4 OF THE REVIEW
PAGE 3 (continued)
Question I(continued
4) I
5) D
6) I
7) I
Question II
8) I
9) I
10) D
11) I
12) I
13) D
14) D
Question III
15) D
16) I
17) D
18) Li
Question 19
a) Al
b) S
c) Br
d) Na
e) F
Question 20
a) gallium
b) oxygen
c) chorine
d) bromine
PAGE 4 (On Back)
PAGE 5
1. K2S
2. SnCl4
3. * Typo: Dihydrogen
monosulfide: H2S
4. CaO
5. AlF3
6. N3O5
7. Fe2(CO3)3
8. SF6
9. NH4OH
10. Mg3(PO4)2
11. K2S, SnCl4, CaO,
AlF3, Fe2(CO3)3,
Al(OH)3, Mg3(PO4)2
12. Ionic –metal and a
nonmetal
Molecular – 2
nonmetals
PAGE 5 (continued)
13. CaO or K2O
14. Calcium oxide or
Potassium oxide
15. CO, CO2
16. Carbon monoxide, carbon
dioxide
PAGE 6
1. 2KCl → 2K+Cl2
2. 2C8H18+25O2 →
16CO2+18H2O
3. Zn +H2SO4 → H2+ZnSO4
4. 2Na+H2O → 2H2+Na2O
5. No Reaction
6. Cl2+2NaBr → Br2+2NaCl
7. Fe + Pb(NO3)2 →Pb +
Fe(NO3)2
8. No Reaction
9. Ca + 2HCl → H2 +CaCl2
10. BaCl2(aq)+(NH4)2CO3(aq) →
2 NH4Cl(aq) +BaCO3(s)
11. No Reaction (all aqueous)
12. Pb(NO3)2(aq)+K2CO3(aq) →
2KNO3(aq) +PbCO3(s)
13. 3AgNO3(aq)+Na3PO4(aq) →
3NaNO3(aq)+Ag3PO4(s)
PAGE 7
1. CO
2. C2H5O2N
3. COCl2
a)
Molecule / Ion
Lewis Structure
VSEPR numbers
220
EDG
Linear
MG
Linear
: 𝑵 ≡ 𝑵:
(none)
Linear
Linear
𝑯 − 𝑪 ≡ 𝑵:
220
Linear
Linear
440
Tetrahedral
Tetrahedral
431
Tetrahedral
Trigonal
pyramidal
321
Trigonal
planar
Bent
330
Trigonal
planar
Trigonal planar
642
Octahedral
Square planar
550
Trigonal
bipyramidal
Trigonal
bipyramidal
541
Trigonal
bipyramidal
Seesaw
11) CO2
12) N2
13) HCN
14) SO42-
15) ClO31-
16) SO2
(has resonance)
17) CO32(has resonance)
18) XeF4
19) PCl5
20) SeF4