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MOLE CONCEPT

Unit of measure for matter. MOLE CONCEPT. Number of particles in one mole = Avogadro’s number = 6.02 X 10 23 602 000 000 000 000 000 000. How many molecules are present in 4 moles of H 2 O? How many atoms are present?. SOLUTION:

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MOLE CONCEPT

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  1. Unit of measure for matter MOLE CONCEPT Number of particles in one mole = Avogadro’s number = 6.02 X 10 23 602 000 000 000 000 000 000

  2. How many molecules are present in 4 moles of H2O? How many atoms are present? SOLUTION: One mole of any substance contains 6.02 X 10 23particles, therefore: (4 moles) 6.02 X 10 23 = 2.41 X 10 24 molecules mole Since there are 3 atoms per H2O molecule, the total number of atoms is: (3 atoms) 2.41 X 10 24 molecules = 7.23 X 10 24 atoms molecule

  3. MOLAR MASS • Mass of one mole = mass of one atom/molecule expressed in grams rather than atomic mass unit (amu) 1 amu = based on 1/12 the mass of C-12 (most common carbon isotope) Example: 1 atom of He = 4 amus 1 mole of He = 4 grams 1 molecule of O2 = 2 x 16 amus/O = 32 amus 1 mole of O2 = 32 grams

  4. FORMULA GIVEN WEIGHT MOLAR MASS NUMBER OF MOLES = GW MM n =

  5. How many moles of carbon atoms are contained in 4 g of carbon? The atomic mass of carbon is 12 amu, therefore the molar mass of carbon is 12 grams. 4 g X 1 mole = 0.333 mole C 12 g CONVERSION FACTOR (from periodic table)

  6. 2. How many moles of water are there in 36 g of water? SOLUTION: The molecular mass of H2O is 18 amu. The molar mass of H2O is 18 g. 36 g X 1 mole = 2 moles H2O 18 g

  7. 3. Calculate the mass of aluminum carbonate (Al2(CO3)3) in 5.85 moles of the compound. In Al2(CO3)3 , there are 2 Al, 3 C and 9 O Formula mass = (2 X 27 g/Al) + (3 X 12 g/C) + (9 X 16 g/O) = 234 g Molar mass = 234 g Mass of Al2(CO3)3 = 5.85 moles X 234 g = 1369 g

  8. MOLAR VOLUME Volume of one mole of solid and liquids = varies from one substance to another based on their density Example: 1 mole of H2O (density = 1.00 g/mL) has a mass of 18 grams and will therefore occupy 18 mL 1 mole of NaCl (density = 2.165 g/mL) has a mass 58 g (Na = 23 g + Cl = 35 g) and would occupy a volume of 26.8mL (58 g /2.165 g/mL) Volume of one mole of gas =equal to 22.4 liters at standard temperature (0oC) and pressure (1 atm or 760 mm Hg) (STP) 1 mole of O2 gas = 22.4 L at STP 1 mole of He = 22.4 L at STP

  9. How many moles of nitrogen are present in 4.48 liters of nitrogen at STP? Since there are 22.4 liters of any gas at STP, the solution is 4.48 L X 1 mole = 0.2 moles N2 22.4 L CONVERSION FACTOR

  10. PERCENT COMPOSITION • Percent by mass of each element present in the compound. % by mass of each element Total mass of element X 100% Total mass of compound =

  11. What is the percentage composition of H2O? % H in H2O 2 X 1 g x 100% = 18 g 11.11 % = % O in H2O 1 X 16 g x 100% = 18 g 88.89% = TO CHECK = 100.00%

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