Mole Conversions
What is the mass of 2 moles of water (H₂O)?
36 grams
Explanation: Molar mass of H₂O = 18 g/mol; 2 moles × 18 g/mol = 36 g.)
What number must you multiply by after dividing the mass of an element by the mass of the compound to find percent composition?
100
This term describes the simplest whole-number ratio of atoms in a compound.
empirical formula
A compound is 36.86% nitrogen (N) and 63.14% oxygen (O). Its molar mass is 76 g/mol. Determine its empirical
Empirical formula: N₂O₃
Assume 100 g: N = 36.86 g, O = 63.14 g.
Convert to moles:
N: 36.8614.01≈2.63 mol14.0136.86≈2.63mol
O: 63.1416.00≈3.95 mol16.0063.14≈3.95mol
Divide by smallest (2.63): N: 1, O: 1.5 → Multiply by 2: N₂O₃.
Empirical mass: 2×14.01+3×16.00=76 g/mol2×14.01+3×16.00=76g/mol
Which NBA player became the first in league history to average a triple-double for an entire season, and in what year did he achieve this feat?
Russell Westbrook
2016-2017
How many moles are in 1.204×10241.204×1024 atoms of carbon?
2 moles
Explanation: Use Avogadro's number: 1.204×10246.022×1023=26.022×10231.204×1024=2 moles.
What is the percent composition of oxygen (O) in water (H₂O), given the molar mass of water is 18 g/mol and oxygen is 16 g/mol?
89%
Molar mass of water (H₂O) = 18 g/mol
Molar mass of oxygen (O) = 16 g/mol
The formula for percent composition is:
Percent Composition=
(Mass of Element/Molar Mass of Compound)×100
Percent Composition of O=(18g/mol)/(16g/mol)×100
A compound contains 48.0% carbon, 4.0% hydrogen, and 48.0% oxygen. This is its empirical formula.
C₄H₄O₃
A compound contains 40.0% carbon (C), 6.7% hydrogen (H), and 53.3% oxygen (O). Its molar mass is 180 g/mol. Determine its empirical
CH₂O
Assume 100 g: C = 40.0 g, H = 6.7 g, O = 53.3 g.
Convert to moles:
C: 40.012.01≈3.33 mol12.0140.0≈3.33mol
H: 6.71.008≈6.65 mol1.0086.7≈6.65mol
O: 53.316.00≈3.33 mol16.0053.3≈3.33mol
Divide by smallest (3.33): C: 1, H: 2, O: 1 → CH₂O.
Empirical mass: 12.01+2×1.008+16.00=30.03 g/mol12.01+2×1.008+16.00=30.03g/mol.
In 2022, this player became the all-time leading goal scorer in international soccer history, surpassing Ali Daei’s record of 109 goals.
Cristiano Ronaldo
How many atoms are in 12 grams of carbon (C)?
6.022×10236.022×1023 atoms
Explanation: Molar mass of carbon = 12 g/mol; 12 g = 1 mole; 1 mole = 6.022×10236.022×1023 atoms.
Calculate the percent composition of sulfur (S) in sulfuric acid (H₂SO₄), given the molar masses: H = 1 g/mol, S = 32 g/mol, O = 16 g/mol.
32.65%
The empirical formula of a compound with 36.0% carbon, 4.0% hydrogen, 28.0% nitrogen, and 32.0% oxygen.
C₃H₄N₂O₂
A compound is 26.56% potassium (K), 38.03% oxygen (O), and the remainder chromium (Cr). Determine its empirical formula.
K₂Cr₂O₇
Assume 100 g: K = 26.56 g, O = 38.03 g, Cr = 100 - 26.56 - 38.03 = 35.41 g.
Convert to moles:
K: 26.5639.10≈0.68 mol39.1026.56≈0.68mol
O: 38.0316.00≈2.38 mol16.0038.03≈2.38mol
Cr: 35.4152.00≈0.68 mol52.0035.41≈0.68mol
Divide by smallest (0.68): K: 1, O: 3.5, Cr: 1 → Multiply by 2: K₂Cr₂O₇.
This NFL team holds the record for the most Super Bowl appearances
New England Patriots
At STP, how many atoms are in 11.2 liters of neon gas (Ne)?
3.011×10233.011×1023 atoms
Explanation: At STP, 11.2 liters = 0.5 moles; 0.5 moles × 6.022×10236.022×1023 atoms/mol = 3.011×10233.011×1023 atoms.
What is the percent composition of water in magnesium sulfate heptahydrate (MgSO₄·7H₂O), and water is 126 g/mol?
51.22%
The molar mass of magnesium sulfate heptahydrate (MgSO₄·7H₂O) is calculated by summing the atomic masses of its constituent elements:
Magnesium (Mg): 24.305 g/mol
Sulfur (S): 32.07 g/mol
Oxygen (O): 16.00 g/mol (multiplied by 11, as there are 4 in MgSO₄ and 7 in 7H₂O)
Hydrogen (H): 1.008 g/mol (multiplied by 14, as there are 14 in 7H₂O)
Molar Mass of (MgSO₄·7H₂O)=24.305+32.07+(11×16.00)+(14×1.008)
=24.305+32.07+176.00+14.112=246.487 g/mol=24.305+32.07+176.00+14.112=246.487g/mol
A compound with 11.25% carbon and 88.75% chlorine has this empirical formula. Its molecular formula mass is 320 g/mol.
C₃Cl₈
A compound is 49.48% carbon (C), 5.19% hydrogen (H), 16.48% oxygen (O), and 28.85% nitrogen (N). Its molar mass is 194 g/mol. Determine its empirical
C₄H₅N₂O
Assume 100 g: C = 49.48 g, H = 5.19 g, O = 16.48 g, N = 28.85 g.
Convert to moles:
C: 49.4812.01≈4.12 mol12.0149.48≈4.12mol
H: 5.191.008≈5.15 mol1.0085.19≈5.15mol
O: 16.4816.00≈1.03 mol16.0016.48≈1.03mol
N: 28.8514.01≈2.06 mol14.0128.85≈2.06mol
Divide by smallest (1.03): C: 4, H: 5, O: 1, N: 2 → C₄H₅N₂O.
Empirical mass: 4×12.01+5×1.008+2×14.01+16.00=97.10 g/mol4×12.01+5×1.008+2×14.01+16.00=97.10g/mol.
This player holds the record for the most NBA All-Star Game MVP awards, with four total wins.
Kobe Bryant
What is the mass of 1.806×10241.806×1024 molecules of carbon dioxide (CO₂)?
132 grams
Explanation:
Convert molecules to moles: 1.806×10246.022×1023=36.022×10231.806×1024=3 moles.
Molar mass of CO₂ = 44 g/mol; 3 moles × 44 g/mol = 132 g.
What is the percent composition of iron (Fe) in potassium ferricyanide (K₃[Fe(CN)₆])?
16.96%
Molar masses of elements:
Iron (Fe): 55.85 g/mol
Potassium (K): 39.10 g/mol
Carbon (C): 12.01 g/mol
Nitrogen (N): 14.01 g/mol
Molar mass of K₃[Fe(CN)₆]:
Potassium (K): 3 × 39.10 = 117.3 g/mol
Iron (Fe): 1 × 55.85 = 55.85 g/mol
Carbon (C): 6 × 12.01 = 72.06 g/mol
Nitrogen (N): 6 × 14.01 = 84.06 g/mol
Total molar mass = 117.3 + 55.85 + 72.06 + 84.06 = 329.27 g/mol Total molar mass = 117.3 + 55.85 + 72.06 + 84.06 = 329.27 g/mol
Percent composition of iron (Fe):
55.85329.27×100≈16.96%329.2755.85×100≈16.96%
Caffeine has 49.48% carbon, 5.19% hydrogen, 16.48% oxygen, and 28.85% nitrogen. Its empirical? (molar mass = 194.19 g/mol).
C₄H₅N₂O
A compound is 11.25% carbon (C) and 88.75% chlorine (Cl). Its molar mass is 320 g/mol. Determine its empirical
C₃Cl₈
Assume 100 g: C = 11.25 g, Cl = 88.75 g.
Convert to moles:
C: 11.2512.01≈0.937 mol12.0111.25≈0.937mol
Cl: 88.7535.45≈2.503 mol35.4588.75≈2.503mol
Divide by smallest (0.937): C: 1, Cl: 2.67 → Multiply by 3: C₃Cl₈.
when did fortnite come out
2017