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Section 10.1 Measuring Matter

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.

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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. #)

  10. Mole Mountain

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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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