Name__________________________________________ Date____________ Period________
Chemistry Mid-Year Review
Read ALL the problems. Complete as many as you feel necessary for you exam preparation.
Concentrate on the ones you do NOT know how to do. There are some occasional references to
ions or compounds that were outside of the scope of our particular class. Feel free to look up /
access internet / use other resources to complete. The answers provided below are NOT
guaranteed. Please email me if you find an error.
Unit 1
1. What are the steps of the scientific method?
:a process to identify and prove the cause and effect relationship between an independent and a
dependent variable. Often it involves and observation/question, a hypothesis, an experimental
design/procedure, the collection and analyzing of data, and making a conclusion.
2. What is an experimental control?
: a test group or set-up which has predictable results / used for comparison
3. What is a controlled variable?
: a condition that could affect the results that is held constant during the experiment
4. What is difference between an independent variable and a dependent variable?
: the independent variable is the cause (purposefully change/manipulated) while the
dependent variable is the measured effect.
5. What is the difference between qualitative data and quantitative data?
: qualitative is a relative observation; whereas quantitative is a numerical observation
6. Determine the correct number of significant digits for the figures below and write each number in
scientific notation
a) 0.93
2
b) 1.008
4
c) 340
2
d) 10001 5
e) 0.097
2
f) 15.96
4
g) 39.5
3
h) 10100 3
7. Add or subtract the following numbers. Round to the correct amount of significant digits and
scientific notation
a) 7.623 + 85.0+ 9.815 =102.4
b) 10.96 – 5.555 =5.4
c) 230.72 + 0.00861
=230.73
d) 9.0731 + 0.00078 =9.0739
e) 10.96 – 5.5
=5.5
f) 23.6 – 16.1218 =7.5
8. Multiple or Divide the following measured numbers. Round to the correct amount of significant digits
and scientific notation NOTE: b and d were intended as scientific notation, please correct on your copy.
a) 2.695 x 33.20 x 1.5611 =139.7
b) (3.2 x 103)(4.21 x 102)÷ 6.28 x 10-8 =2.15 x 1013
c) 8.032/0.591
=13.6
d) (2.500 x 106)(3.92 x 10-3) =9.80 x 103
e) (72.21 x 6.42) + 7.050
=53.3
f) (6000260 x 0.005201) ÷ 5.206 = 3.121 x 104
9. Answer the questions below using the figures provided.
a. What is the reading of the water level in the test tube? 18.0 mL
b. What is length of the ruler at point G? Point E? Point B? Point J? Point F?
G = 9.67cm E = 10.30cm B = 11.30cm J = 11.70cm F = 12.00 cm
(MUST measure to 1/100ths, values +/- a hundredth or two are acceptable)
10. Solve the follow dimensional analysis problems. Solve all problems using scientific notation and
significant digits
a. 3 m = 3 x 102 cm
b. 1 cm = 1 x 10-4 μm
c. 20 mm = 2 cm
d. 1 m = 1 x 10-3 km3
. 15g = 1.5 x 10 mg
f. 2 L = 2 x 103 mL
11. What is a significant figure?
: is any number in a measurement that is certain (compared to a standard) PLUS one estimated value.
12. a. What is an element?
:a pure substance that cannot be broken down into simpler substances by chemical means.
b. What is a compound?
:a pure substance that can be broken down into simpler substances by chemical means.
c. What is a substance?
:a material that cannot be separated into simpler substances by physical means.
d. What is an atom?
: the smallest particle that retains its chemical identity (protons/neutrons and electrons do NOT!)
13. Answer the following questions about density.
a. What is density, and what is the mathematic equation used to find the density of a substance
density = Mass / Volume
Calculate the following densities. Use Significant Digits in your answer.
b. 252 mL of a solution with a mass of 500 g = 1.98g/mL
c. A 6.75 g solid with a volume of 5.35 cm3 = 1.25 g/cm3
d. 50.0 mg of a gas which occupies a volume of 0.0064 L = 7.8 x 10-3g/mL
14. What is Accuracy? What is precision?
How do they differ when speaking about them in scientific terms.
Accuracy is how close a measurement is to the true or known value and is expressed in percent error.
Precision is how repeatable/reproducible a measurement is and is expressed as range or deviation.
15.
a.
Working in the laboratory, a student find the density of a piece of pure aluminum to be 2.85
g/cm3. The accepted value for the density of aluminum is 2.699 g/cm3. What is the student's
percent error? = 5.59%
b. A student experimentally determines the specific heat of water to be 4.29 J/g x Co. He then looks
up the specific heat of water on a reference table and finds that is is 4.18 J/g x Co. What is his
percent error? = 2.63%
c. A student takes an object with an accepted mass of 200.00 grams and masses it on his own
balance. He records the mass of the object as 196.5 g. What is his percent error? = -1.750%
16. Precision Problems
Several lab groups measure the density of aluminum. Here is their data:
Team 1
Team 2
Team 3
Team 4
Team 5
Team 6
Team 7
3
3
3
3
3
3
2.65 g/cm
2.75 g/cm
2.80 g/cm
2.77 g/cm
2.60 g/cm
2.65 g/cm
2.68 g/cm3
a. What is the average density? 2.70 g/cm3
b. Subtract the highest value from the lowest value: 0.20 g/cm3 Divide this number by 2 0.10 g/cm3
c. The precision of the measurement can be shown as 2.70  0.10 g/cm3.
d. Here is more data. Is this more precise, less precise, or the same precision as the above data? The
same.
Team 1
2.60 g/cm3
Team 2
2.70 g/cm3
Team 3
2.80 g/cm3
Team 4
2.75 g/cm3
Team 5
2.65 g/cm3
Team 6
2.62 g/cm3
Team 7
2.78 g/cm3
Unit 2
17. The Periodic Table
a. A proton has a +1/positive charge, a neutron has a 0/neutral charge, and an electron has
-1/negative charge
b. Group 2A (column 2) has a charge of +2
c. Group 6A (column 16) had a charge of -2
d. An element with a positive or negative charge is called an ion
e. An ion with a negative charge is called an anion
f. An ion with a positive charge is called a cation
g. An ionic bond is the transfer of electrons and a covalent bond is a sharing of electrons
18. Label each of the sections of the element below
Atomic Number (Number of Protons)
Chemical Symbol
Atomic Mass (Average of ALL Isotopes)
Mass Number is the sum of protons + neutrons
a
19. Fill out the following table based on the information given. Use your periodic table to help complete it.
Element
Atomic #
Atomic
Charge
# of protons # of neutrons # of electrons
Mass
Lithium
3
7
+1
3
4
3
Nitrogen
7
14
0
7
7
7
Fluorine
9
19
-1
9
10
10
Argon
18
40
0
18
22
18
Tarbium
65
159
+2
65
94
63
Naming Compounds – Ionic and Covalent
20. Name the following chemical compounds.
a. CaF2
calcium fluoride
c. P2O3
diphorphorus trioxide
e. AgNO3
silver nitrate
g. Al2(CO)3
aluminum carbonate
i. NaBr
sodium bromide
k. H2SO4
sulfuric acid
m. NH3
ammonia
o. Ti(SO4)2
titanium (IV)sulfate
q. SO2
sulfur dioxide
s. NaNO3
sodium nitrate
b. NaF
sodium fluoride
d. MgSO4
magnesion sulfate
f. C2S7
dicarbon heptasulfide
h. SrS
strontium sulfide
j. NaOH
sodium hydroxide
l. MgI2
magnesium iodide
n. CaNO2
calcium nitritr
p. N3O8
trinitrogen octoxide
r. Na2O
sodium oxide
t. BF5
boron pentafluoride
21. Give the correct formula for the following compounds
a. disilicon tetraselenide Si2Se4
b. cobalt (II) chloride CoCl2
c. copper (I) acetate CuC2H3O2
d. lithium phoshide Li3P
e. sodium fluoride NaF
f. manganese (IV) nitride Mn3N4
g. iron (III) sulfite Fe2(SO3)3
h. boron trichloride BF3
i. silver oxide Ag2O
j. carbon tetraarsenide CAs4
k. strontium carbonite SrCO2
l. beryllium astatide BeAt2
m. pentasilicon dichloride Si5Cl2
n. nickel (II) selenide NiSe
o. potassium permanganate KMnO4
p. cesium carbonate Cs2CO3
q. sodium hydroxide NaOH
r. ammonia hydroxide NH4OH
s. tetraphosphorus octatelluride P4Te8
t. calcium iodide CaI2
22. Calculate the Molar Mass of the following compounds.
a. Cu(CN)2 = 116.0 g/mol
b. C6H6 =78.0g/mol
c. SmO = 166.4g/mol
d. H3PO4 = 98.0g/mol
e. K2SO4 = 174.3g/mol
f. ZnO = 81.4g/mol
g. (NH4)3PO3 = 133.0g/mol
h. BaCO3 = 197.3g/mol
i. NaHCO3 = 84.0g/mol
23. Calculate the Percent Composition of the following elements
a. Nitrogen in Cu(CN)2 = 24.1%
b. Carbon in C6H6 = 92.3%
c. Oxygen in SmO = 90.4%
d. Phosporus in H3PO4 = 30.7%
e. Oxygen in K2SO4 = 36.7%
f. Zinc in ZnO = 80.3%
g. Complete Percent Composition
in (NH4)3PO3
h. Complete Percent
Composition in BaCO3
i. Complete Percent Composition
in NaHCO3
=31.6%N,9.0%H,22.6%P,36.1%O = 69.6%Ba, 6.1%C, 24.3%O
=27.3%Na1.2%H,14.3%C,57.1%O
24. a. What is the definition of Avogadro’s number
Avogadro’s number is the number of atoms in exactly 12.0 grams of carbon 12 isotope.
b. What does STP stand for, and what are the measurements for each
STP means standard temperature of 0o C and pressure of 1 atm
How many moles are in 521 grams of HCl = 14.3 mole HCl
How many atoms are in 41 grams of K = 6.3 x 10 23atoms K
How many Liters of O2 gas are in 35 grams = 24.5 L O2
How many grams of CO2 gas are in 245 Liters = 481 g CO2
How many moles are in 51 x 1026 molecules of HNO3 = 8.4 x 103 moles HNO3
How many grams are in 4.7 moles of H2CO3 = 290 g H2CO3 (rounded for sig fig from 291.4)
How many molecules are in 72.3 Liters of NH3 gas = 1.94 x 1024 molecules NH3
How many moles are in 83 Liters of Cyanide gas = 3.7 mol CN
How many grams are in 11.9 x 1021 atoms of Kr = 1.66 g Kr
c.
d.
e.
f.
g.
h.
i.
j.
k.
25. Figure out the empirical formulas for each of the following compounds
a. A compound that is 25.41g S and 38.11g O SO3
b. A compound that has 1.04g K, 0.700g Cr, and 0.86g O K2CrO4
c.
d.
e.
f.
g.
A compound that is 53.7% Fe and 46.30% S Fe2O3 (from Fe1O1.5)
A compound that has 4.04g of N and 11.16g of oxygen P2O5 (from P1O2.5)
43.67% P and 56.33% O P2O5 (from P1O2.5)
39.3% Na and 60.7%Cl NaCl
24.58% K, 34.81% Mn, and 40.50% O KMnO4
Unit 3
26. What is the definition of a physical property, chemical property, and chemical reactions? Give 3
examples of physical changes? Give 3 examples of chemical changes?
A physical property is observed with senses and the act of observing it does NOT change the chemical
make up of the material. A chemical property is observed by reaction the material with another substance
and the act of observing it produces a new chemical substance. Examples of physical change may be
grinding, melting, cutting, boiling, etc. Examples of chemical change may be rusting/oxidizing,
burning/combusting, reacting with acid or bases, etc.
27. What is a reactant? Which side of the equation are the reactants on?
Reactants are the substances that exist before the reaction. They are listed on the left side.
28. What is a product? Which side of the equation are the products on?
Products are the substances that exist after the reaction. They are listed on the right side.
29. Is the mass of the reactants equal to, greater than, or lesser than the mass of the products?
The Law of Conservation of Mass says the mass of the reactants is always EQUAL to the mass of
the products. This is because the number and type of atoms before the reaction are the same after
the reaction; the bond are broken, the atoms are rearranged and new bonds are formed. (The Law
of Conservation of Matter).
30. What is a coefficient? What is subscript? What do each signify and where are they located in a
problem?
A coefficient tells how many molecules, where a subscript tells how many atoms in ONE
molecule. (See example below).
31. Give examples of a coefficient and of a subscript.
3H2O The 3 is a coefficient; it means 3 water molecules.
The 2 is the subscript; it means 2 hydrogen atoms in EACH of the 3 water molecules.
32. Answer the following questions below.
a. 5 Al2CO3
How many molecules? 5
How many atoms of Aluminum?
10
How many atoms of Carbon? 5
How many atoms of Oxygen
15
b. CH3COOH
How many molecules? 1
How many Atoms of Hydrogen?
4
How many atoms of Carbon? 2
How many atoms of Oxygen? 2
c. 4 (NH4)3PO3
How many molecules? 4
How many Atoms of Nitrogen? 12
How many atoms of Hydrogen? 48
How many atoms of Phosphorus? 4
How many atoms of Oxygen? 12
33. First, write out the following word equations. Second, write the formula equations. Lastly, balance
the equations and make sure to indicate which state/phase each is in!
a. Carbon gas and Nitrogen gas combine to form cyanide gas
carbon + nitrogen  cyanide
C + N2  CN
C + N2  2CN
2C + N2  2CN
Steps:
Finished balanced equation with phase notations:
2C(g) + N2(g)  2CN(g)
b. Liquid pentane and Oxygen gas combine to make Carbon Dioxide gas and Water
pentane + oxygen  carbon dioxide + water
C5H12(g) + 8O2(g)  5CO2(g) + 6H2O(g)
c. Salt is broken down to form Sodium metal and Chlorine gas
sodium chloride  sodium + chlorine
2NaCl(s)  2Na(s) + Cl2(g)
d. Hydrogen gas and Oxygen gas form Water when bonded together.
hydrogen + oxygen  water
2H2(g) + O2(g) --> 2H2O(l)
e. Aqueous Copper Chloride combines with aqueous Sodium Sulfate to form Aqueous Copper Sulfate
and Sodium Chloride.
copper(I) chloride + sodium sulfate  copper(1) sulfate + sodium chloride
2CuCl (aq) + Na2SO4(aq)  Cu2SO4(s) + 2NaCl(aq)
Copper (II) would be: copper(II) chloride + sodium sulfate  copper(II) sulfate + sodium chloride
CuCl2 (aq) + Na2SO4(aq)  CuSO4(s) + 2NaCl(aq)
Copper (I) would be:
34. Balance the following equations
a. 2Fe
+ 3H2SO4 
Fe2(SO4)3
+ 3H2
b.
2C2H6
+
7O2 
6H2O
+ 4CO2
c.
3KOH
+
H3PO4 
K3PO4
+ 3H2O
d.
SnO2
+
2H2 
Sn
+ 2H2O
e.
4NH3
+
5O2 
4NO
+ 6H2O
f.
2KNO3
+
H2CO3 
K2CO3
+ 2HNO3
g.
B2Br6
+
6HNO3 
2B(NO3)3
+ 6HBr
h.
2BF3
+
3Li2SO3 
B2(SO3)3
+ 6LiF
i.
4(NH4)3PO4
+
3Pb(NO3)4 
Pb3(PO4)4
+ 12NH4NO3
j.
SeCl6
+
O2 
SeO2
+ 3Cl2
35. Balance the following equations and identify the type of reaction shown
a.
2Al + 2H3PO4  2AlPO4 + 3H2
TYPE Single Replacement
b.
NH4Cl + NaNO3  NaCl + 2H2O + N2O
c.
5Cl2 + 10NaOH 8NaCl + 2NaHClO3 + 4H2O
d.
TYPE Double /Decompostion
2Pb(NO3)2  2PbO +4NO2 +O2
Type(Not able to discern)
TYPE Decomposition
e.
2C3H8 + 7O2  6CO +8H2O
TYPE Incomplete Combustion
f.
2KI + Cl2  2KCl + I2
TYPE Single Replacement
g.
CO2 + C  2CO
TYPE Synthesis
h.
3H2O + P2O5  2H3PO4
TYPE Synthesis
i.
CaSO4 + Na2CO3  CaCO3 + Na2SO4
TYPE Double Replacement
j.
H2SO4 + 2 KOH  K2SO4 + 2H2O
TYPE Double Replacement
36. Write It, Balance it, Identify it!!!
a. potassium iodide + chlorine  potassium chloride + iodine
2KI + Cl2  2KCl + I2
TYPE Single Replacement
b. sulfuric acid + potassium hydroxide potassium sulfate + dihydrogen monoxide TYPE Double Replacement
H2SO4 + 2 KOH  K2SO4 + 2H2O
c. carbon dioxide + carbon carbon monoxide
CO2 + C  2CO
TYPE Synthesis
d. calcium sulfate + sodium carbonate  calcium carbonate + sodium sulfate
CaSO4 + Na2CO3  CaCO3 + Na2SO4
TYPE Double Replacement
e. water + diphosphorous pentoxide phosphorous acid
3H2O + P2O5  2H3PO4
TYPE Synthesis
f. aluminum + phosphoric acid  hydrogen + aluminum phosphate
2Al + 2H3PO4  3H2 + 2AlPO4
g. ammonium chloride + sodium nitrite sodium chloride + water + N2O
NH4Cl + NaNO3  NaCl + 2H2O + N2O
TYPE Single Replacement
TYPE Double /Decompostion
h. chlorine + sodium hydroxide sodium chloride + sodium hypochlorite + water
5Cl2 + 10NaOH 8NaCl + 2NaHClO3 + 4H2O
i. lead (II) nitrate -- (heated)  lead (II) oxide + nitrogen dioxide + oxygen
2Pb(NO3)2  2PbO +4NO2 +O2
j. propane + oxygen carbon monoxide + dihydrogen monoxide
2C3H8 + 7O2  6CO +8H2O
37. What is an activity series and how does it help us?
TYPE (Not able to discern)
TYPE Decomposition
TYPE Incomplete Combustion
Ranks the activity of metals (and Hydrogen) for cationic single
replacement reactions and separately for non metals for anionic
signle replacement reactions. This allows one to predict whether a
single replacement reaction is spontaneous or not.
38. Use the activity series provided, predict which of the
following reactions will occur.
(Yes or No answer)
a.) Ag + ZnCl2 
No
b.) Zn + AgNO3 
Yes
c.) NaCl + I2 
No
d.) K + CaO 
Yes
e.) Mg + HCl 
Yes
39. Predict the products and balance the equation for those
reactions that do occur in #38.
38b:
Zn + 2AgNO3  2Ag + Zn(NO3)2
38d:
2K + CaO Ca + K2O