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Section 10.1 Measuring Matter

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1 Section 10.1 Measuring Matter
Explain how a mole is used to indirectly count the number of particles of matter. molecule: two or more atoms that covalently bond together to form a unit Relate the mole to a common everyday counting unit. Convert between moles and number of representative particles. mole Avogadro’s number Chemists use the mole to count atoms, molecules, ions, and formula units.

2 Counting Particles Chemists need a convenient method for accurately counting the number of atoms, molecules, or formula units of a substance. The _______ is the SI base unit used to measure the amount of a substance. 1 mole is the amount of atoms in 12 g of pure carbon-12, or 6.02  1023 atoms. The number is called ___________________

3 Converting Between Moles and Particles
Conversion factors must be used. Moles to particles Number of molecules in 3.50 mol of sucrose

4 Converting Between Moles and Particles (cont.)
Particles to moles Use the inverse of Avogadro’s number as the conversion factor.

5 Section 10.2 Mass and the Mole
Relate the mass of an atom to the mass of a mole of atoms. conversion factor: a ratio of equivalent values used to express the same quantity in different units Convert between number of moles and the mass of an element. Convert between number of moles and number of atoms of an element. molar mass A mole always contains the same number of particles; however, moles of different substances have different masses.

6 The Mass of a Mole 1 mol of copper and 1 mol of carbon have different masses. Because !!!! One copper atom has a different mass than 1 carbon atom. So same number of atoms, but different masses. (ie 100 bricks or 100 feathers)

7 The Mass of a Mole (cont.)
__________________ is the mass in grams of one mole of any pure substance. The molar mass of any element is numerically equivalent to its atomic mass and has the units g/mol.

8 Using Molar Mass Moles to mass

9 Using Molar Mass (cont.)
Convert moles to mass by multiplying by the molar mass Convert mass to moles with the inverse molar mass conversion factor. (1 / molar mass) Convert moles to atoms with Avogadro’s number as the conversion factor. Convert atoms to moles with the inverse of Avagadro’s number (1 / Av. #)


11 Mole Mountain

12 Section 10.3 Moles of Compounds
Recognize the mole relationships shown by a chemical formula. Calculate the molar mass of a compound. Convert between the number of moles and mass of a compound. Apply conversion factors to determine the number of atoms or ions in a known mass of a compound. representative particle: an atom, molecule, formula unit, or ion

13 Section 10.3 Moles of Compounds (cont.)
The molar mass of a compound can be calculated from its chemical formula and can be used to convert from mass to moles of that compound.

14 Chemical Formulas and the Mole
Chemical formulas indicate the numbers and types of atoms contained in one unit of the compound. One mole of CCl2F2 contains one mole of C atoms, two moles of Cl atoms, and two moles of F atoms.

15 The Molar Mass of Compounds
The molar mass of a compound equals the molar mass of each element, multiplied by the moles of that element in the chemical formula, added together. ie: mass of H2O = mass of 2 moles of H + mass of 1 mole of O. The molar mass of a compound demonstrates the law of conservation of mass.

16 Converting Moles of a Compound to Mass
For elements, the conversion factor is the molar mass of the element. The procedure is the same for compounds, except that you must first calculate the molar mass of the compound.

17 Section 10.4 Empirical and Molecular Formulas
Explain what is meant by the percent composition of a compound. percent by mass: the ratio of the mass of each element to the total mass of the compound expressed as a percent Determine the empirical and molecular formulas for a compound from mass percent and actual mass data. percent composition empirical formula molecular formula A molecular formula of a compound is a whole-number multiple of its empirical formula.

18 Percent Composition The percent composition by mass of any element in a compound can be found by dividing the mass of the element by the mass of the compound and multiplying by 100.

19 Percent Composition (cont.)
The percent by mass of each element in a compound is the ____________________ of a compound. Percent composition of a compound can also be determined from its chemical formula.

20 Molecular formula of hydrogen peroxide = H2O2
Empirical Formula The _____________________________ for a compound is the smallest whole-number mole ratio of the elements. The empirical formula may or may not be the same as the molecular formula. Molecular formula of hydrogen peroxide = H2O2 Empirical formula of hydrogen peroxide = HO

21 Molecular Formula The _______________________ specifies the actual number of atoms of each element in one molecule or formula unit of the substance. Molecular formula is always a whole-number multiple of the empirical formula.

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