Mid-Term Review Answers:
1. a. Na2Cl b. HCl c. CCl4 d. P2O5 e. (NH4)4SO4 f. BaCl2 g. Li2S h. K3P i. CoBr2 j. Fe2O3
2. a. beryllium chloride b. sodium sulfide c. copper (I) chloride d. calcium hydroxide e. magnesium nitrate f.
sodium phosphate g. iron (II) sulfide h. nickel (II) sulfate i. silver bromide j. silicon tetrachloride k. sulfur
hexafluoride
3. Ca2+ O24. Chemical change – bread baking, milk souring, wood burning; Physical change – dry ice subliming, ice melting,
water boiling
5. 2.36 mol SO3/1 X 80.06 g SO3/1 mol SO3 = 189 g SO3; 2.36 mol SO3/1 X 6.02 molecules SO3/1 mol SO3 = 1.42 X
1023 molecules SO3
6. 100 degrees C + 273 = 373 K; 303 K – 273 = 30 degrees C
7. 2 Fe + 2 H3PO4  2FePO4 + 3 H2 = single displacement
8. Potassium-39 has 19 protons, 20 neutrons, and 19 electrons
9. Ca, Mg, Be
10. Any 3 in the same column – e.g F, Cl, Br or O, S, Se or N, P, As or Li, Na, K
11. See p. 72-74 in textbook
12. See page 68 in textbook
13. See page 68 in textbook
14. A gain of electrons results in a negative ion (anion) and a loss of electrons results in a positive ion (cation)
15. 40 Ca – an atom of Calcium with 20 protons and 20 neutrons (mass # is 40)
20
16. Mass # = # of protons and # neutrons; protons and neutrons are in the nucleus – similar masses; electrons are
outside the nucleus – extremely small
17. Isotopes differ from each other in having different numbers of neutrons. So atoms differ in their mass. Separate
by centrifuging.
18. Metal elements are to the left of the stair-step line; nonmetals are to the right of the stair step line; Metalloids
are located along the stair step line (e.g. Si, Ge, As, B, Sb, Te)
19. An orbital is an area described by a mathematical function that is a place where electrons of a particular energy
may be found. One orbital can hold two electrons. (s – orbital spherical; p – dumbbell shape; f – cloverleaf
shape. An s sublevel can hold 2 electrons; p – 3 orbitals – holds 6 electrons; and d – 5 orbitals – holds 10
electrons
20. Sulfur: 1s22s22p63s23p4; Sulfide, S2-: 1s22s22p63s23p6; Potassium: 1s22s22p63s23p64s1; K+:1s22s22p63s23p6
21. See pages 100-103 in textbook
22. H2SO4 + KOH  KHSO4 + H2O – double displacement
23. One mole of H2SO4 would yield one mole of H2O
24. 3 Cl2 + 2 Al  2AlCl3 - 75.0g AlCl3/1 X 1 mol AlCl3/133.33g AlCl3 X 3 mol Cl2/2 mol AlCl3 = 0.844 mol Cl2 ;
0.844mol Cl2/1 X 22.4L Cl2/1 mol@STP = 18.9 L Cl2 @STP
25. Assume 100 g sample: 38.7 g C/12.01 g C/mol C = 3.22 mol C, 9.7gH/1.008g/molH = 9.62 mol H, 51.6g
O/16.00g/mol = 3.22 mol O – divide by smallest # which is 3.22 and you get 1 C, 3 H, 1 O, The empirical formula
is CH3O – the molar mass of this formula is 31 g/mol; The molar mass of the molecular formula given is 62.1
g/mol. 31 X 2 = 62 so the molecular formula = 2x empirical formula = C2H6O2