Chemical Quantities and Reactions
Chemical Quantities and Reactions Thursday, September 20, 2012 11:27 AM
5.1 The Mole Avogadro's Number • Small particles such as atoms, molecules, and ions are counted using the mole. 1 mole = 6.02 x 1023 items Avogadro’s number 602 000 000 000 000 000 000 000 = 6.02 x 1023 Mole of Atoms 1 mole of an element = 6.02 x 1023 atoms of that element 1 mole of water = 6.02 x 1023 molecules H20 1 mole of sodium = 6.02 x 1023 atoms of sodium Avogadro's Number Avogadro’s number, 6.02 x 1023, can be written as an equality and as two conversion factors. Equality: 1 mole = 6.02 x 1023 particles Conversion Factors: 6.02 x 1023 particles ------------------------1 mole Moles of Elements in a Formula The subscripts in a formula show: • the relationship of atoms in the formula • the moles of each element in 1 mole of compound Aspirin C9H8O4 1 molecule: 9 atoms of C 8 atoms of H 4 atoms of O 1 mole: 9 moles of C 8 moles of H 4 moles of O EX: How many atoms of O are in 0.150 mole of aspirin, C9H8O4? 0.150 mol C9H8 4 mol O 6.02 x 10^23 1mole aspirin 1 mole O 5.2 Molar Mass The molar mass • is the mass of 1 mole of an element • is the atomic mass expressed in grams
EX: Molar Mass of the Compound C2H6O 2 C (2 x 12.01) 6H (6 x 1.008) 1O (1 x 16.00) -----------------46 g/mol Calculations Using Molar Mass Molar mass conversion factors • are fractions (ratios) written from the molar mass. • relate grams and moles of an element or compound. • for methane, CH4, used in gas stoves and gas heaters, is 1 mole of CH4 = 16.0 g of CH4 (molar mass equality) Conversion factors: 16.0 g CH4/1 mole CH4 EX: Allyl sulfide, C6H10S, is a compound that has the odor of garlic. How many moles of C6H10S are in 225 g? (6x 12.01) + (10 x 1.008) + (32.07) = 114.21 114.21 g/mol 225 g C6H10S 1 mole 114.12 g 5.3 Chemical Reactions and Equations A chemical change • occurs when a substance is converted into one or more substances with different formulas and different properties • may be observed by the formation of bubbles, a change in color, or production of solid
Symbols Used in Chemical Equations To write a chemical equation • an arrow indicates reactants form products • reactants are written on the left side of the arrow • products are written on the right side of the arrow • multiple reactants or products are separated by a + sign • the delta {Δ} sign indicates that heat is used to start the reaction EX: C(s) + O2 (g) ---> CO2 (g) = (calculate answer) = 1.97 moles C6H10S
5.1 The Mole Avogadro's Number • Small particles such as atoms, molecules, and ions are counted using the mole. 1 mole = 6.02 x 1023 items Avogadro’s number 602 000 000 000 000 000 000 000 = 6.02 x 1023 Mole of Atoms 1 mole of an element = 6.02 x 1023 atoms of that element 1 mole of water = 6.02 x 1023 molecules H20 1 mole of sodium = 6.02 x 1023 atoms of sodium Avogadro's Number Avogadro’s number, 6.02 x 1023, can be written as an equality and as two conversion factors. Equality: 1 mole = 6.02 x 1023 particles Conversion Factors: 6.02 x 1023 particles ------------------------1 mole Moles of Elements in a Formula The subscripts in a formula show: • the relationship of atoms in the formula • the moles of each element in 1 mole of compound Aspirin C9H8O4 1 molecule: 9 atoms of C 8 atoms of H 4 atoms of O 1 mole: 9 moles of C 8 moles of H 4 moles of O EX: How many atoms of O are in 0.150 mole of aspirin, C9H8O4? 0.150 mol C9H8 4 mol O 6.02 x 10^23 1mole aspirin 1 mole O 5.2 Molar Mass The molar mass • is the mass of 1 mole of an element • is the atomic mass expressed in grams
EX: Molar Mass of the Compound C2H6O 2 C (2 x 12.01) 6H (6 x 1.008) 1O (1 x 16.00) -----------------46 g/mol Calculations Using Molar Mass Molar mass conversion factors • are fractions (ratios) written from the molar mass. • relate grams and moles of an element or compound. • for methane, CH4, used in gas stoves and gas heaters, is 1 mole of CH4 = 16.0 g of CH4 (molar mass equality) Conversion factors: 16.0 g CH4/1 mole CH4 EX: Allyl sulfide, C6H10S, is a compound that has the odor of garlic. How many moles of C6H10S are in 225 g? (6x 12.01) + (10 x 1.008) + (32.07) = 114.21 114.21 g/mol 225 g C6H10S 1 mole 114.12 g 5.3 Chemical Reactions and Equations A chemical change • occurs when a substance is converted into one or more substances with different formulas and different properties • may be observed by the formation of bubbles, a change in color, or production of solid
Symbols Used in Chemical Equations To write a chemical equation • an arrow indicates reactants form products • reactants are written on the left side of the arrow • products are written on the right side of the arrow • multiple reactants or products are separated by a + sign • the delta {Δ} sign indicates that heat is used to start the reaction EX: C(s) + O2 (g) ---> CO2 (g) = (calculate answer) = 1.97 moles C6H10S
