Percent Composition
UNISTRUCTURAL | Identification (30sec)
What is percent composition?
The percentage by mass of each element in a compound.
UNISTRUCTURAL | Identification (30sec)
What quantity must you always convert to moles when determining an empirical formula?
The mass (or percent) of each element
UNISTRUCTURAL | Identification (30sec)
How will you know the multiplier to be used for the empirical formula to identify the molecular formula?
molecular mass ÷ empirical mass
UNISTRUCTURAL | Identification (20sec)
1 mole contains how many particles?
6.022 × 10²³
MULTISTRUCTURAL | Multiple Choice (45sec)
What is the molar mass of CO₂?
A. 12.001 g/mol
B. 16.000 g/mol
C. 44.009 g/mol
D. 28.019 g/mol
C. 44.009 g/mol
MULTISTRUCTURAL | Multiple Choice (45sec)
A compound contains 75% carbon and 25% hydrogen. What is its empirical formula?
A. C₂H₆
B. CH₄
C. CH
D. C₃H₈
B. CH₄
MULTISCTRUCTURAL | Multiple Choice (45sec)
EF = CH₂, molar mass = 28 g/mol. What is the MF?
A. CH₂
B. C₂H₄
C. C₃H₆
D. C₄H₈
B. C₂H₄
MULTISTRUCTURAL | Multiple Choice (45sec)
How many moles are in 12 g of carbon?
A. 0.50 mol
B. 1.00 mol
C. 2.00 mol
D. 3.00 mol
B. 1.00 mol
MULTISTRUCTURAL | True or False (45sec)
Oxygen contributes more to the molar mass of CO₂ than carbon does.
TRUE
RELATIONAL | Identification (90sec)
Answer only.
A compound is 40% C, 6.7% H, and 53.3% O. Identify its Empirical Formula.
CH₂O
MULTISTRUCTURAL | True or False (45sec)
The empirical mass of C12H22O4 is 115.148 g/mol
False
MULTISTRUCTURAL | True or False (45sec)
8 mol NH₃ reacts with exactly 6 mol O₂ in the equation NH₃ + O₂ → N₂ + H₂O
True
RELATIONAL | Problem Solving (2mins)
Show your solution.
Using the formula CO₂, compute the percent composition of carbon in the compound.
27.29% carbon
RELATIONAL | Problem Solving (2mins)
Show your solution.
A biodegradable plastic contains 52.14% C, 34.73% O, and 13.13% H. Determine its Empirical Formula.
C₂H₆O
RELATIONAL | Problem Solving (2mins)
Show your solution.
A compound has an empirical formula of C₂H₃O and a molar mass of 172 g/mol.
Determine the molecular formula.
MF = C₈H₁₂O₄
RELATIONAL | Problem Solving (2mins)
Show your solution.
During a STEM Science Expo, a group demonstrates the reaction between ammonia and oxygen to form nitrogen gas:
NH3+O2→N2+H2O
Their setup produces 5.0 moles of NH₃ from a generator. How many grams of O₂ do they need to react with the 5.0 moles of NH₃ completely?
120 g of O₂
EXTENDED ABSTRACT | Problem Solving (3mins)
Show your solution.
A STEM class analyzes an unknown compound made of C, O, and H.
Their data shows:
The compound has a molar mass of 180 g/mol
72 g of the 180 g are carbon
96 g are oxygen
The rest is hydrogen
Identify the percent composition of each.
40% C, 53% O, 6.7% H
RELATIONAL | Problem Solving (3mins)
Show your solution.
A STEM lab analyzes a biodegradable plastic with 62.58% C, 9.63% H, and 27.79% O. Determine the empirical formula.
C₆H₁₁O₂
EXTENDED ABSTRACT | Problem Solving (3mins)
Show your solution.
A Grade 11 STEM research group analyzes an unknown organic compound used in a biodegradable coating.
From laboratory data, the compound is found to contain:
54.53% carbon
9.15% hydrogen
36.32% oxygen
Further testing shows that the compound has a molar mass of 132 g/mol. Determine the molecular formula.
C₆H₁₂O₃
EXTENDED ABSTRACT | Problem Solving (3mins)
Show your solution.
A Grade 11 STEM class is building a model fertilizer reactor.
They simulate making ammonia (NH₃) using nitrogen and hydrogen.
They have a tank containing 120 grams of nitrogen gas. How many grams of ammonia can they theoretically produce?
150 g of NH₃