6. compare the physical and chemical properties of acids and bases.\n7. explain how the concentrations of…

Brief Explanations:

6. Acids taste sour, react with metals to produce hydrogen gas, and turn blue - litmus paper red. Bases taste bitter, feel slippery, and turn red - litmus paper blue. Chemically, acids donate protons ($H^+$) in solution, while bases accept protons or release hydroxide ions ($OH^-$).
7. In a neutral solution, the concentration of hydrogen ions $[H^+]$ equals the concentration of hydroxide ions $[OH^-]$, i.e., $[H^+]=[OH^-]=1\times10^{- 7}\ mol/L$ at $25^{\circ}C$. In an acidic solution, $[H^+]>[OH^-]$, and in a basic solution, $[H^+]<[OH^-]$.
8. According to the Arrhenius theory, an acid is a substance that dissociates in water to produce hydrogen ions ($H^+$). Many compounds with hydrogen atoms do not dissociate in water to release $H^+$ ions. For example, in methane ($CH_4$), the hydrogen atoms are covalently bonded and do not ionize in water to form $H^+$ ions.

Answer:

6. Physical: Acids taste sour, turn blue - litmus red; Bases taste bitter, feel slippery, turn red - litmus blue. Chemical: Acids donate $H^+$, Bases accept $H^+$ or release $OH^-$.
7. Neutral: $[H^+]=[OH^-]$; Acidic: $[H^+]>[OH^-]$; Basic: $[H^+]<[OH^-]$.
8. Compounds with hydrogen don't always dissociate to release $H^+$ in water as required by Arrhenius theory.