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Chemical Reactions
 

Chemical Reactions

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    Chemical Reactions Chemical Reactions Presentation Transcript

    • Chemistry 30S Unit 3 – Chemical Reactions
    • CHEMICAL REACTIONS PROTONS ELECTRONS NEUTRONS ATOMIC MASS ATOMIC NUMBER mass number Bohr Models
      • You may recall from earlier science courses that all atoms, except hydrogen, are made of 3 basic particles: protons, neutrons and electrons.
      • You may also recall that each element has a unique number of protons, which is indicated by its atomic number or Z number(the symbol for atomic number is Z).
      CHEMICAL REACTIONS Defining Isotopes
      • The number of neutrons in each atom varies, even between atoms of the same element. For example, potassium can exist as three different atoms. All three atoms contain 19 protons, but one potassium atom has 20 neutrons, another 21 neutrons and yet another has 22 neutrons.
      • Atoms that have the same number of protons but differ in their number of neutrons are called isotopes . Generally, most elements exist as more than one isotope.
      CHEMICAL REACTIONS Defining Isotopes
      • As you would expect, if different isotopes have different numbers of neutrons, they will have different masses. The mass number or A number of an atom is the sum of the protons and neutrons found in the nucleus of that atom.
      CHEMICAL REACTIONS Defining Isotopes
      • If we look at the potassium isotopes above, the isotope containing 19 protons and 20 neutrons will have a mass number of 39 (19 + 20). We call this isotope potassium-39. The isotope that has 19 protons and 21 neutrons will have a mass number of 40 (19 + 21) and is called potassium-40.
      CHEMICAL REACTIONS Defining Isotopes
      • Chemists have designed a symbol for each isotope that includes the element’s symbol, its atomic number (Z) and its mass number (A).
      CHEMICAL REACTIONS Defining Isotopes
    • CHEMICAL REACTIONS C 12 6 Mass Number Atomic Number
      • Chemists devised a system of mass for atoms called atomic mass units , abbreviated amu or µ .
      • The atomic mass unit is based on the carbon atom with 6 protons and 6 neutrons having a mass of 12 amu’s .
      • Therefore, one amu is one-twelfth the mass of a carbon atom.
      CHEMICAL REACTIONS Atomic Mass
    • CHEMICAL REACTIONS Isotopes & Atomic Mass
      • The atomic mass of an element is the average atomic mass of all the chemical element's isotopes as found in a particular environment, weighted by isotopic abundance.
      • Isotopes are forms of an element whose nuclei have the same atomic number ( the number of protons in the nucleus ) but different atomic masses because they contain different numbers of neutrons .
      CHEMICAL REACTIONS Isotopes & Atomic Mass
      • A tomic mass, is the average mass of all the naturally occurring, non-radioactive isotopes of an element. The average is weighted, based on the Percent of Abundance of each of those isotopes. Atomic mass is the decimal number most commonly associated with each element's symbol on the Periodic Chart.
      CHEMICAL REACTIONS Isotopes & Atomic Mass
      • The values for the atomic mass of the elements are calculated by summing the products of the different individual Isotope Masses multiplied by the decimal equivalent of their percent of abundance values.
      • Both terms, Isotope Mass and Percent of Abundance, must be given. They can only be determined experimentally, or by looking up the values that a chemist has already determined experimentally.
      CHEMICAL REACTIONS Isotopes & Atomic Mass
    • CHEMICAL REACTIONS Find the AVERAGE ATOMIC MASS of the Rubber Stoppers using the relative abundance of the various isotopes .
    • CHEMICAL REACTIONS Find the AVERAGE ATOMIC MASS of the Rubber Stoppers using the relative abundance of the various isotopes . Group 1 - # 00 Rubber Stopper Group 2 - # 0 Rubber Stopper Group 3 - #1 Rubber Stopper Group 4 - #2 Rubber Stopper Group 5 - #3 Rubber Stopper Group 6 - #4 Rubber Stopper
      • Example:
        • (Mass of Isotope 1)x(Percent Abundance/100) + (Mass of Isotope 2)x(Percent Abundance/100) + (Mass of Isotope 3)x(Percent Abundance/100) + +etc. = Atomic Weight
      CHEMICAL REACTIONS Isotopes & Atomic Mass ONLINE EXAMPLE http://chemlab.pc.maricopa.edu/periodic/U.html#is
    • CHEMICAL REACTIONS
    • CHEMICAL REACTIONS Chemical Formulas
      • A chemical formula is a shorthand method to represent compounds that uses the elements' symbols and subscripts. The chemical formula gives the following information:
        • The different elements in the compound.
        • The number of atoms of each element in the compound.
      CHEMICAL REACTIONS Chemical Formulas
    • CHEMICAL REACTIONS Chemical Formulas - Review What is PO 4 ?
    • CHEMICAL REACTIONS
    • CHEMICAL REACTIONS Question 1
    • CHEMICAL REACTIONS Question 2
    • CHEMICAL REACTIONS Question 2a
    • CHEMICAL REACTIONS Question 2b
    • CHEMICAL REACTIONS Question 3 Li 1+ and Cl 1- Ca 2+ and O 2- Na 1+ and S 2- Al 3+ and I 1- Ba 2+ and F 1
    • CHEMICAL REACTIONS Question 4 Sodium and bromine Potassium and oxygen Aluminum and sulfur Barium and chlorine Lithium and oxygen Silver and chlorine
    • CHEMICAL REACTIONS Question 5
    • CHEMICAL REACTIONS Question 6 Question 7
    • CHEMICAL REACTIONS Question 8 Question 9
    • CHEMICAL REACTIONS Question 10
    • CHEMICAL REACTIONS Question 11
      • Polyatomic ions are charged particles (usually negative) made up of groups of atoms bonded together. They act in very similar ways to single atomic ions of the same charge.
      • The atoms that make up a polyatomic ion collectively have one charge.
      CHEMICAL REACTIONS Polyatomic Ions
      • These compounds to follow ARE NOT binary compounds. They contain three or more elements, as opposed to only two in a binary compound.
      • The cations used will be a mix of fixed charges AND variable charges. You must know which are which.
      • You must also know the charges associated with each polyatomic ion. For example, NO 3 ¯ is called nitrate and it has a minus one charge (not minus 3).
      CHEMICAL REACTIONS Nomenclature & Polyatomic Ions
      • When more than one polyatomic ion is required, parenthesis are used to enclose the ion with the subscript going outside the parenthesis.
        • For example, Fe(NO 3 ) 2 . This means that two NO 3 ¯ are involved in the compound.
      CHEMICAL REACTIONS Nomenclature & Polyatomic Ions
    • CHEMICAL REACTIONS Polyatomic Ion List
      • Example #1 - write the name for Fe(NO 3 ) 2
      • Step #1 - decide if the cation is one showing variable charge. If so, a Roman numeral will be needed. In this case, iron does show variable charge.
        • If a variable charge cation is involved, you must determine the Roman numeral involved. You do this by computing the total charge contributed by the polyatomic ion. In this case, NO 3 ¯ has a minus one charge and there are two of them, making a total of minus 2.
        • Therefore, the iron must be a positive two, in order to keep the total charge of the formula at zero.
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #1 - write the name for Fe(NO 3 ) 2
      • Step #2 - determine the name of the polyatomic ion. Nitrate is the name of NO 3 ¯.
      • The correct name is iron(II) nitrate. The common name would be ferrous nitrate.
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #2 - write the name for NaOH
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #3 - write the name for KMnO 4
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #4 - write the name for Cu 2 SO 4
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #5 - write the name for Ca(ClO 3 ) 2
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #6 - write the name for Fe(OH) 3
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #1 - write the formula for copper(II) chlorate
      • Step #1 - the first word tells you the symbol of the cation. In this case it is Cu.
      • Step #2 - the Roman numeral WILL tell you the charge on the cation. In this case it is a positive two.
      • Step #3 - the polyatomic formula and charge comes from the second name. In this case, chlorate means ClO 3 ¯.
      CHEMICAL REACTIONS Given Name, Write the Formula
      • Example #1 - write the formula for copper(II) chlorate
      • Step #4 - remembering the rule that a formula must have zero total charge, you write the formula Cu(ClO 3 ) 2 .
      CHEMICAL REACTIONS Given Name, Write the Formula
      • Example #2 - write the formula for silver cyanide
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #3 - write the formula for lead (IV) hydroxide
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #4 - write the formula for sodium phosphate
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #5 - write the formula for sodium nitrate
      CHEMICAL REACTIONS Given Formula, Write the Name
      • Example #6 - write the name for barium carbonate
      CHEMICAL REACTIONS Given Formula, Write the Name
    • CHEMICAL REACTIONS
      • Molecular Mass – is the collective mass of all the atoms that are found in a molecule of a covalent compound
      • Formula Mass – is the collective mass of all the atoms that are found in a molecule of an ionic compound.
      CHEMICAL REACTIONS Calculating Mass of Compounds in AMU’s
      • What is the molecular mass of glucose?
      CHEMICAL REACTIONS Calculating Mass of Compounds in AMU’s
      • What is the molecular mass of aspirin?
      • C 9 H 8 O 4
      CHEMICAL REACTIONS Calculating Mass of Compounds in AMU’s
      • What is the formula mass of aluminum hydroxide?
      CHEMICAL REACTIONS Calculating Mass of Compounds in AMU’s
      • What is the formula mass of barium hydrogen sulfite?
      • Ba(HSO 3 ) 2
      CHEMICAL REACTIONS Calculating Mass of Compounds in AMU’s