CHEMISTRY MIDTERM REVIEW
CHEMISTRY MIDTERM REVIEW
Areas Covered
1. CONVERSIONS IN METRIC UNITS: How many kilograms are in 143 grams?
2. CONVERSIONS
... [Show More] WITH ENGLISH UNITS: How many milliliters are in 13.5 oz?
3. Is ATM (atmospheres) a standard number?
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 1 L 1000 mL
8 oz 2 cups 2 pt 1.06 qt 1 L
= 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
Comparing the reactants and the products
OXIDATION REDUCTION
Gain Oxygen Lost oxygen
Lose Hydrogen Gains Hydrogen
Lose electrons Gains electrons
Increases oxidation number Decreases oxidation number
NaBr + Cl2 NaCl + Br2
+1 -1 0 +1 -1 0
Bromine oxidation number INCREASED
Chlorine oxidation number DECREASE
-5 -4 -3 -2 -1 0 1 2 3 4 5
What is oxidized: __NaBr__________________ REDUCING AGENT
What is reduced: __Cl2_____________________ OXIDIZING AGENT
Oxidizing agents (cause oxidation; get reduced)
Reducing agent (cause reduction; get oxidized) [Show Less]