Also, we will not cover the Kapustinski equation or Structure Maps. Feel free to keep using the CaRIne software to help you
CHEM 41 Assignment 2. Answers
1. Write a balanced chemical equation for the reaction of an alkali metal with a halogen. Use M to represent the metal and
X to represent the halogen. Is the reaction likely to be exothermic or endothermic? Is the product ionic or covalent?
M (s) + ½ X2 (l) Æ MX (s) exothermic reaction, product is an ionic solid
2. Write a balanced chemical equation for the general reaction of an alkaline earth metal with oxygen. Use the symbol M to
represent the alkaline earth element. Is the reaction likely to be exothermic or endothermic? Is the product ionic or
M (s) + ½ O2 (l) Æ MO (s) exothermic reaction, product is an ionic solid
3. Would you expect to find calcium naturally occurring in the earth’s crust as a free element? Why or why not?
Calcium is far too reactive (too easily oxidized) to survive in the environment in the metallic form. Remember the reaction
done in the lab where the element is placed in cold water, and produces the hydroxide and hydrogen gas spontaneously.
4. Place the following oxides in order of increasing basicity: CO2, SiO2, and SnO2.
See page 49 of the notes; the tin oxide is amphoteric, whereas carbon and silicon oxides are acidic. A reasonable guess from
their relative electronegativities is that SnO2 < SiO2 < CO2. Note that none are strong acid precursors.
5. Complete and balance equations for the following reactions.
(a) 2 Li(s) + Cl2(g) Æ 2 LiCl (s)
(b) 2 Ca(s) + O2(g) Æ 2 CaO (s)
6. Write balanced chemical equations for the reaction of hydrogen gas with oxygen, chlorine, nitrogen.
H2 (g) + ½ O2 (g) Æ H2O (l)
H2 (g) + Cl2 (g) Æ 2 HCl (g) H2 (g) + N2 (g) Æ 2 NH3 (g) (under catalysis)
7. Write an equation for the reaction of sodium and hydrogen. Name the product. Is it ionic or covalent? Predict one
physical property and one chemical property of this compound.
Na (s) + ½ H2 Æ