Unit 6: The Mole - mrhee.weebly.com
Transcript of Unit 6: The Mole - mrhee.weebly.com
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Unit 6: The Mole
Note: Most of this unit will be solving problems, with many examples done in class on the board.
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Recall:1 mol = !6.02x1023 particles
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Recall:1 mol = !6.02x1023 particles1 mol = !the molar mass of an! ! ! ! ! ! atom or compound
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Recall:1 mol = !6.02x1023 particles1 mol = !the molar mass*of an! ! ! ! ! ! atom or compound
Synonyms for molar mass:! - molecular mass! ! - formula mass! ! ! - formula weight
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Section 7.3 i) Calculating molar massii) Mole-mass conversions
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Page 230Percent composition:the percent by mass of each element in a compound.
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Practice:What is the percent composition of water?
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What is the percent composition of magnesium chloride?
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Section 7.4 Determining Chemical Formulas
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Empirical formula:the smallest whole-number ratio of atoms in a compound.
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Practice:1. Determine the empirical formula of a ! compound composed of: ! ! ! ! 81.82% carbon! ! ! ! 18.18 % hydrogen
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1. Determine the empirical formula of a compound composed of:
! ! ! ! 81.82% carbon! ! ! ! 18.18 % hydrogen! ! (assume a 100-gram sample!)
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Note:If mole ratio is within +/-0.1 of a whole
number, round to that number.
If not, multiply by 2/2, 3/3, etc., to obtain a whole-number ratio.
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2. Determine the empirical formula of a compound composed of:
! ! ! 68.4% chromium! ! ! 31.6% oxygen
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3. Determine the empirical formula of a compound composed of:
! ! ! 26.6% sulfur! ! ! 53.2% oxygen! ! ! 20.2% magnesium
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4. Determine the empirical formula of a compound composed of:
! ! ! 9.61g oxygen! ! ! 7.33g magnesium! ! ! 0.61g hydrogen?
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4. Determine the empirical formula of a compound composed of: ! ! ! 9.61g oxygen! ! ! 7.33g magnesium! ! ! 0.61g hydrogen. ! ! ! What is its name?
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Molecular formula: the actual number of atoms in a compound.
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Molecular formula: the actual number of atoms in a compound…
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Molecular formula: the actual number of atoms in a compound... It will be a whole-number multiple of the empirical formula (1, 2, etc…).
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Practice 1:The empirical formula of a compound is: C3H4N2.
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Practice 1:The empirical formula of a compound is: C3H4N2. What is its molecular formula if the molar mass has been determined to be 204.2 g/mol?
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Practice 2:i. Determine the empirical formula of a compound composed of:! ! 40.29% boron! ! ! 7.51% hydrogen! ! ! ! 52.20% nitrogen
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Practice 2:i. Determine the empirical formula of a compound composed of:! ! 40.29% boron! ! ! 7.51% hydrogen! ! ! ! 52.20% nitrogenii. If the molar mass of the compound is 80.51g, what its molecular formula?
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Pages 231-232The Formula of a Hydrate
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Hydrate: An ionic compound that has a specific number of water molecules bound within its crystal structure.
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Hydrate: A compound that has a specific number of water molecules bound to its atoms.
Prefixes mono, di, tri, etc. are used to indicate the number of water molecules contained in the hydrate formula.
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Examples
Heating
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!! ! Hydrate ------->Anhydrate
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Anhydrate: A hydrate that has had its water molecules removed.
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Anhydrate: A hydrate that has had its water molecules removed.(aka “desiccant,” a drying agent that absorbs water from the air)
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=See Dry Lab Practice Worksheet=