In the reaction NH3(g) + H2O(l) <=> NH4+(aq) + OH-(aq), identify an acid according to Arrhenius and explain why.

(II) Fluorine
Fluorine (F) has an atomic number of 9, so it has 7 valence electrons. In a fluorine molecule ($\text{F}_2$), two fluorine atoms share one pair of electrons to form a single covalent bond, and each fluorine atom has three lone pairs of electrons.

$$\stackrel{\bullet \bullet}{\stackrel{\bullet \bullet}{\text{F}}} \stackrel{\bullet}{\times} \text{F} \stackrel{\times \times}{\stackrel{\times \times}{\stackrel{\times \times}{}}}$$

b) With reference to the diagrams in (a), state why fluorine is more reactive than nitrogen.
The triple covalent bond in nitrogen ($\text{N}_2$) is very strong and requires a large amount of energy to break, making nitrogen relatively unreactive. The single covalent bond in fluorine ($\text{F}_2$) is much weaker and easier to break, which makes fluorine highly reactive.

22. Study the reaction below and answer the questions that follow. $\text{NH}_{3(g)} + \text{H}_2\text{O}_{(l)} \rightleftharpoons \text{NH}_{4(aq)}^+ + \text{OH}_{(aq)}^-$

a) Define the term acid according to Arrhenius.
An Arrhenius acid is a substance that dissociates in water to produce hydrogen ions ($\text{H}^+$) or hydronium ions ($\text{H}_3\text{O}^+$).

b) Identify an acid in the forward reaction.
$\text{H}_2\text{O}$

c) Explain your answer in (b) above.
Water ($\text{H}_2\text{O}$) acts as an acid because it donates a proton ($\text{H}^+$) to ammonia ($\text{NH}_3$) in the forward reaction, forming the hydroxide ion ($\text{OH}^-$).

23. Give the IUPAC names of the following compounds:

(I) $\text{CH}_3\text{COOCH}_2\text{CH}_3$
Ethyl ethanoate

(II) $\text{CH}_3\text{CH}_2\text{COOH}$
Propanoic acid

(III) $\text{CH}_2=\text{C}(\text{Br})\text{CH}_3$
2-bromopropene