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CHEM 120 Midterm Exam Review
Course Number: CHEM120
Course Title: Introduction to General, Organic & Biological Chemistry with Lab
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(Complete solutions and resources for the course exam)
,CHEM 120 – Midterm Review
1.) CONVERSIONS IN METRIC UNITS
How many kilograms are in 143 grams?
Using KHDBDCM
Starting with Grams (g) – base unit. Moving to kilograms (kg); move the decimal three spaces to
the right
143 g – 0.143 g
Using conversion factors
KNOW that kilo = 1000 base
143 g x (1 kg/1000g ) = 0.143 kg
2.) CONVERSIONS WITH ENGLISH UNITS
How many milliliters are in 13.5 oz?
MUST USE CONVERSION FACTORS (oz, lb, feet, inches…)
Always start with what you know…. Figure out where to go
13.5 oz ? mL
13.5 oz 1 cup 1 pt 1 qt 1L 1000 mL
8 oz 2 cups 2 pt 1.06 qt 1L
= 398 mL are in 13.5 oz
, Question: is ATM (atmospheres) a standard number?
Answer; No, it’s a unit. There’s not a particular number there. The gas constant has a number
and a unit because it is a constant; atmospheres will differ depending on the problem
Stoichiometry: Practice questions.
22.0 g of propane will combine with what mass (g) of O2?
C3H8 + 5O2 3CO2 + 4H2O
c- 3 c -3
H–8 H-8
O- 10 O – 6 + 4 = 10
GIVEN: want:
22.0 g of C3H8 ? g O2
Balanced chem equation
C3H8 + 5O2 3CO2 + 4H2O
Periodic table (moles to grams or grams to moles ONE COMPOUND)
1.) Check to make sure the equation is balanced – DONE
2.) Start with the known
3.) … were you given moles? If not, find moles using the periodic table to take grams to
moles of one compound.
4.) From moles, use the balanced chemical equation. BCE compares moles to moles of
different compounds
5.) If you were looking for moles, stop. If you need grams, use the periodic table to convert
moles – grams of the same compound.
22.0 g C3H8 1 mol C3H8 5 mol O2 32.0 g O2
44.1 g C3H8 1 mol C3H8 1 mol O2
= 79.8 g O2
Calculate the molar (molecular) mass of C3H8 = units are g/mol NOT grams
Mass – units are grams
ANY MASS from the Periodic Table has units of grams per mole (g/mol)
3 x 12.011 g/mol + 8 x 1.008 g/mol = 44.097 g/mol
1 mole C3H8 = 44.097 g
CALCULATE THE MOLAR (MOLECULAR) MASS OF O2. 31.998 G/MOL
1 mol O2 = 31.998 g
OXIDATION/REDUCTION
Pg. 218, figure 8.2
CHEM 120 Midterm Exam Review
Course Number: CHEM120
Course Title: Introduction to General, Organic & Biological Chemistry with Lab
• Well Explained Answers
• Secure high grade
• Best feedback (rated) document by students
(Complete solutions and resources for the course exam)
,CHEM 120 – Midterm Review
1.) CONVERSIONS IN METRIC UNITS
How many kilograms are in 143 grams?
Using KHDBDCM
Starting with Grams (g) – base unit. Moving to kilograms (kg); move the decimal three spaces to
the right
143 g – 0.143 g
Using conversion factors
KNOW that kilo = 1000 base
143 g x (1 kg/1000g ) = 0.143 kg
2.) CONVERSIONS WITH ENGLISH UNITS
How many milliliters are in 13.5 oz?
MUST USE CONVERSION FACTORS (oz, lb, feet, inches…)
Always start with what you know…. Figure out where to go
13.5 oz ? mL
13.5 oz 1 cup 1 pt 1 qt 1L 1000 mL
8 oz 2 cups 2 pt 1.06 qt 1L
= 398 mL are in 13.5 oz
, Question: is ATM (atmospheres) a standard number?
Answer; No, it’s a unit. There’s not a particular number there. The gas constant has a number
and a unit because it is a constant; atmospheres will differ depending on the problem
Stoichiometry: Practice questions.
22.0 g of propane will combine with what mass (g) of O2?
C3H8 + 5O2 3CO2 + 4H2O
c- 3 c -3
H–8 H-8
O- 10 O – 6 + 4 = 10
GIVEN: want:
22.0 g of C3H8 ? g O2
Balanced chem equation
C3H8 + 5O2 3CO2 + 4H2O
Periodic table (moles to grams or grams to moles ONE COMPOUND)
1.) Check to make sure the equation is balanced – DONE
2.) Start with the known
3.) … were you given moles? If not, find moles using the periodic table to take grams to
moles of one compound.
4.) From moles, use the balanced chemical equation. BCE compares moles to moles of
different compounds
5.) If you were looking for moles, stop. If you need grams, use the periodic table to convert
moles – grams of the same compound.
22.0 g C3H8 1 mol C3H8 5 mol O2 32.0 g O2
44.1 g C3H8 1 mol C3H8 1 mol O2
= 79.8 g O2
Calculate the molar (molecular) mass of C3H8 = units are g/mol NOT grams
Mass – units are grams
ANY MASS from the Periodic Table has units of grams per mole (g/mol)
3 x 12.011 g/mol + 8 x 1.008 g/mol = 44.097 g/mol
1 mole C3H8 = 44.097 g
CALCULATE THE MOLAR (MOLECULAR) MASS OF O2. 31.998 G/MOL
1 mol O2 = 31.998 g
OXIDATION/REDUCTION
Pg. 218, figure 8.2
