Questions and Answers
What is a mole of the element?
The molar mass of an element is the mass of one mole of that element.
How many moles of NH3 are present in 107.01 g?
6.289 moles
What is the percentage composition of CF4?
13.6% C, 86.4% F
How many grams of CS2 are present in 10.0 moles?
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How many grams of CCl2 are present in 5.0 moles?
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What is the mass of 0.240 moles of glucose, C6H12O6?
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What is the percentage composition of CO?
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How many moles of LiF are present in 10.37 g?
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What is the formula mass for ethyl alcohol, C2H5OH?
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What is the sum of the atomic masses of all the atoms in a formula for a compound?
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What is the formula mass for magnesium chloride, MgCl2?
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What is the percentage composition of CuCl2?
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What is the formula mass for (NH4)2SO4?
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How many grams of H2O are present in 0.20 moles?
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How many moles of NO2 are present in 114.95 grams?
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Study Notes
Moles and Molar Mass
- A mole of an element corresponds to its molar mass, which is the mass of one mole in grams.
- Molar mass can be calculated by dividing the mass of a sample by its number of moles.
Molar Mass Calculations
- For NH3 (molar mass = 17.03 g/mol), 107.01 grams equals approximately 6.289 moles.
- For CS2 (molar mass = 76.15 g/mol), 10.0 moles corresponds to 761.5 grams.
- For CCl4 (molar mass = 153.81 g/mol), 5.0 moles equals 769.05 grams.
- The mass of 0.240 moles of glucose (C6H12O6) is 43.2 grams.
- For H2O (molar mass = 18.02 g/mol), 20 moles equates to 360.4 grams.
Percentage Composition
- In CF4, the percentage composition is 13.6% C and 86.4% F.
- For CO, the percentage composition is 43% C and 57% O.
- In CuCl2, composition is 47.21% Cu and 52.79% Cl.
Formula Mass
- The formula mass is the sum of atomic masses of all atoms in a compound’s formula.
- Ethyl alcohol (C2H5OH) has a formula mass of 46.08 amu.
- Magnesium chloride (MgCl2) has a formula mass of 95.21 amu.
- For ammonium sulfate ((NH4)2SO4), the formula mass is 132.16 amu.
Moles From Given Mass
- Molar mass of LiF is 25.94 g/mol, allowing for 0.3998 moles from 10.37 grams of LiF.
- For NO2 (molar mass = 46.01 g/mol), 114.95 grams gives 2.498 moles.
Studying That Suits You
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Description
Test your knowledge of key concepts from Chemistry Chapter 7 with these flashcards. This quiz covers important terms and definitions related to moles, molar mass, and percentage composition. It's an excellent resource for reinforcing your understanding of chemical calculations.
