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Answer Key to the First Review

Go to the First Unit Review problems.

  1. Basics
  2. An element contains just one type of an atom.
  3. A compound is two or more different atoms bonded together to make neutral particle.
  4. A chemical change will make a new substance (ex. burning), a physical change does not (ex. melting, boiling).
  5. Review your sig figs and how to use them in calculations.
  6. a) D = m/V = 35.94 g/ 3.18 mL = 11.3 g/mL
    b) V = m/D = 72.98 g/ 2.70 g/mL = 27.0 mL
  7. a)

    b)

    The Atom

  8. Look in your book.
  9. proton - p+, 1 amu, in the nucleus; electron - e-, 1/1840 amu, outside the nucleus; neutron - no, 1 amu, in the nucleus.
  10. Rutherford's gold foil experiment. Look in the book for the rest.
  11. An isotope is an atom of an element that has a different number of neutrons.
  12. Cathode Ray Tube experiment. Look in your book.
  13. Fill in the following table. (It includes ions, which are in a later chapter, but might as well cover it now.)
    Element or Ion Name Element or Ion Symbol Atomic Number Atomic Mass # of p+ # of e- # of no charge
    calcium ion Ca+2 20 40 20 18 20 +2
    carbon C 6 13 6 6 7 0
    sulfide ion S-2 16 32 16 18 16 -2
    tin Sn 50 119 50 50 69 0
    iron (III) ion Fe+3 26 56 26 23 30 +3
  14. Atomic Spectra

  15. Thomson - "plum pudding" model, a positive blob with electrons stuck in it. Rutherford - protons in the nucleus, electrons outside of the nucleus. Bohr - nucleus contains protons and neutrons, electrons in definite orbits, or energy levels, outside the nucleus. Quantum Mechanical Model - nucleus with protons and neutrons, electrons in probability regions outside the nucleus.
  16. s - 1 orbital, 2 e- total; p - 3 orbitals, 6 e- total; d - 5 orbitals, 10 e- total; f - 7 orbitals, 14 e- total.
  17. Look in your book.
  18. a) 1s22s22p63s1   b) 1s22s22p63s23p64s23d104p6   c) 1s22s22p63s23p64s23d104p65s24d105p66s24f145d3
  19. VIBGYOR (opposite of ROYGBIV) Remember that red is at 700 nm and violet at 400 nm.
  20. This is best explained by looking at the second part of the atomic spectra page.

    Formulas

  21. a) metal   b) nonmetal   c) metal   d) metalloid   e) nonmetal
  22. Calcium forms a +2 ion when it loses two electrons to become like argon. It is now called the calcium ion.
  23. Phosphorus forms a -3 ion by gaining 3 electrons to become like argon. It is now called the phosphide ion.
  24. A molecular compound is composed of two nonmetals. An ionic compound is formed from oppositely charged particles being attracted, usually a metal and a nonmetal.
  25. KNOW YOUR POLYATOMIC IONS!
  26. a) CaI2 ionic   b) PCl 5 molecular   c) (NH4)2S ionic   d) Cu2HPO3 ionic  
    e) N2O5 molecular   f) Sn(C2O4)2 ionic
  27. a) potassium permanganate   b) tin (II) dichromate   c) disulfur trioxide   d) sodium nitrate  
    e) lead (IV) hydrogen carbonate

    Mole Conversions

  28. The number of grams in one mole is the same as the formula mass.
    Ca(HCO3)2: (1 Ca x 40.08) + (2 H x 1.01) + (2 C x 12.01) + (6 O x 16.00) = 162.12 g/mole
  29. a)
    b)the formula mass of C5H10O2 = 102 g/mol. The molecular mass = 204 g/mol.
    204/102=2. Multiply all by 2 to get C10H20O4

    Chemical Reactions

  30. The five types of reactions are: single replacement, double replacement, combination, decomposition, and combustion. Look in your book or notes for further descriptions.
  31. An equation must be balanced to conserve mass (matter).
  32. a) 2 C   +   O2 --> 2 CO   combination
    b) 2 KClO3 --> 2 KCl   +   3 O2   decomposition
    c) 2 FeCl3   +   3 Ca(OH)2 --> 2 Fe(OH)3   +   3 CaCl2   double replacement
    d) Mg   +   2 AgNO3 --> 2 Ag   +   Mg(NO3)2   single replacement
    e) 2 C4H10   +   13 O2 --> 8 CO2   +   10 H2O   combustion
    f) 4 K   +   O2 --> 2 K2O   combination
  33. Write a balanced net ionic equation for each reaction.
    a) Pb(NO3)2 (aq)   +   2 NaCl(aq) --> PbCl2 (s)   +   2 NaNO3 (aq)
    net ionic = Pb+2(aq)   +   2 Cl-1(aq) --> PbCl2 (s)

    b) Zn(s)   +   2 HCl(aq) --> ZnCl2 (aq)   +   H2 (g)
    net ionic = Zn(s)   +   2 H+1(aq) --> Zn+2(aq)   +  H2 (g)



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