Section 9.3 Acids and Base
Acids and bases are two types of chemical compounds that have unique properties and behavior. Acids are compounds that have a high concentration of hydrogen ions \((H^+)\text{,}\) which they release when they are dissolved in water. Acid tests sour. Orange, lemon, tomato, tamarind, and grapefruit are sour and contain acid in their juice. Bases, on the other hand, have a high concentration of hydroxide ions \((OH^-)\text{,}\) which they release when they are dissolved in water. Base also known as Alkali tests bitter. Cucumber, asparagus, garlic, yam, broccoli, and fish slime are alkaline.
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(It is compeletely prohibited to test any liquid in the laboratory.)
\begin{equation*}
HCl \longrightarrow H^+ +Cl^- \text{dissociation of hydrochloric acid}
\end{equation*}
\begin{equation*}
H_2SO_4 \longrightarrow H^+ +SO_4^- \text{dissociation of sulfuric acid}
\end{equation*}
Acid dissociates into hydrogen ion when dissolve in water.
\begin{equation*}
NaOH \longrightarrow Na^+ +OH^- \text{dissociation of sodium hydroxide base}
\end{equation*}
\begin{equation*}
Ba(OH)_2 \longrightarrow Ba^{2+} +2OH^- \text{dissociation of barium hydroxide base}
\end{equation*}
Base dissociates into hydroxide ion when dissolve in water.
Acids can be classified as either weak or strong, depending on their ability to dissociate in water. A strong acid is an acid that completely dissociates in water, meaning that all of its molecules break apart into ions. Examples of strong acids include hydrochloric acid \((HCl)\text{,}\) sulfuric acid \((H_2SO_4)\text{,}\) and nitric acid \((HNO_3)\text{.}\) These acids have a very low pH and are highly reactive. A weak acid, on the other hand, only partially dissociates in water, meaning that only a small fraction of its molecules break apart into ions. Examples of weak acids include acetic acid \((CH_3COOH)\text{,}\) formic acid \((HCOOH)\text{,}\) and citric acid \((C_6H_8O_7)\text{.}\) These acids have a higher pH than strong acids and are less reactive. The strength of an acid is determined by its dissociation constant (Ka), which is a measure of how easily the acid donates a proton to water. A high Ka value indicates a strong acid, while a low Ka value indicates a weak acid.
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Explanation of dissociation constant (Ka) is out of the course requirement here.
A base is a substance that can accept a proton \((H^+)\) from another substance or donate a hydroxide ion \((OH^-)\) to another substance. Bases can be classified as either strong or weak, depending on their ability to dissociate in water. A strong base is a base that completely dissociates in water, meaning that all of its molecules break apart into ions. Examples of strong bases include sodium hydroxide \((NaOH)\text{,}\) potassium hydroxide \((KOH)\text{,}\) and calcium hydroxide \((Ca(OH)_2)\text{.}\) These bases have a very high pH and are highly reactive. A weak base, on the other hand, only partially dissociates in water, meaning that only a small fraction of its molecules break apart into ions. Examples of weak bases include ammonia \((NH_3)\text{,}\) pyridine \((C_5H_5N)\text{,}\) and trimethylamine \((N(CH_3)_3)\text{.}\) These bases have a lower pH than strong bases and are less reactive. The strength of a base is determined by its dissociation constant (Kb), which is a measure of how easily the base accepts a proton from water. A high Kb value indicates a strong base, while a low Kb value indicates a weak base.
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Explanation of dissociation constant (Kb) is out of the course requirement here.
