University:
Montgomery College
Course:
CHEM 131: Principles of Chemistry I
Academic year:

2020
Views:

426

Pages:

2
Author:

Alexa Livingston

Mole & Molar Mass Mole (mol): the amount of material counting 6.02214 × 1023 particles The value of the mole is equal to the number of atoms in exactly 12 grams of pure carbon-12.  12.00 g C-12 = 1 mol C-12 atoms = 6.022 × 1023 atoms  The number of particles in 1 mole is called Avogadro’s Number (6.0221421 x 1023). 6.022 ×1023 atoms or 1 mol 1 mol 6.022 ×1023 atoms Converting between Number of Moles and Number of Atoms Calculate the number of atoms in 2.45 mol of copper. mol Cu 2.45 mol Cu × A silver ring contains 1.1 x 1022 silver atoms. How many moles of silver are in the ring? Atoms Ag Atoms 6.022 ×1023 atoms 1 mol 24 = 1.48 × 10 atoms Cu mol Ag 1.1 ×1022 atoms Ag × 1 mol 6.022 ×1023 atoms = 1.8 × 10-2 mol Ag Molar Mass: the mass of 1 mol of atoms of an element An element’s molar mass in g/mol is numerically equal to the element’s atomic mass in amu. 1 mol C 12.01 g C or 12.01 g C 1 mol C Converting between Mass and Number of Moles Converting between Mass and Number of Atoms Calculate the moles of carbon in 0.0265 g of pencil lead. How many aluminum atoms are in a can weighing 16.2 g? gC mol C 0.0265 g C × -3 g Al atoms Al mol Al 1 mol C 12.01 g C = 2.21 × 10 mol C 16.2 g Al × 1 mol Al 26.98 g Al = 3.62 × 1023 atoms Al × 6.022 ×1023 atoms 1 mol Avogadro’s number molar mass Moles Gram Formula units (atoms, molecules, ions) Practice Problems 1. How many atoms are there in each of following? (a) 3.75 moles of silver (b) 2.36 moles of xenon (c) 158 kg of phosphorus 2. What is the amount, in moles, of each of the following? (a) 449 g of potassium (b) 11.8 g of Ar (c) 2.16 x 10 24 atoms of lead 3. What is the mass of each of the following? (a) 1.9 x 10 24 (b) 4.87 x 10 (c) 2.33 x 10 atoms of Pb (in g) 25 20 atoms of Zn (in kg) atoms of oxygen (in ng) 4. How many molecules are in 2.50 moles of CO2? 5. Calculate the mass , in grams, of 0.433 mol of calcium nitrate. Hint: Formula Weight of Ca(NO3)2 = (AW of Ca) + 2(AW of N) + 6 (AW of O) 6. Calculate the number of H atoms in 0.350 mol of C6H12O6 References: Tro, Chemistry: A Molecular Approach 2nd ed., Pearson Brown/LeMay/Bursten, Chemistry: The Central Science, 12th ed., Pearson 1. (a) 2.26 × 10 silver atoms; (b) 1.42 × 10 xenon atoms (c) 3.07 × 10 phosphorus atoms 2. (a) 11.5 moles; (b) 0.295 moles Ar; (c) 3.59 moles 2 6 3. (a) ) 6.5 × 10 g; (b) 5.29 kg; (c) 6.19 × 10 ng 24 4. 1.51 x 10 atoms; 5. 71.1 g Ca(NO3)2 6. 2.53 x 1024 H atoms 24 Answers 24 27