Question

1. define the following terms

a. acid
a substance that donates hydrogen ions (h+
b. base
a substance that donates hydroxide ions
c. ph
a measure of the acidity or alkalinity
solution : ph = - log h+
d. buffer

Explanation:

a. According to the Brønsted - Lowry theory, an acid is a substance that donates hydrogen ions (\(H^{+}\)). For example, in the reaction \(HCl + H_{2}O
ightarrow H_{3}O^{+}+Cl^{-}\), \(HCl\) donates \(H^{+}\) to \(H_{2}O\).
b. A base is a substance that accepts hydrogen ions (\(H^{+}\)). In the reaction \(NH_{3}+H_{2}O
ightleftharpoons NH_{4}^{+}+OH^{-}\), \(NH_{3}\) accepts \(H^{+}\) from \(H_{2}O\).
c. \(pH\) is a measure of the acidity or alkalinity of a solution. The formula is \(pH =-\log[H^{+}]\). If \([H^{+}]=1\times10^{- 7}\space mol/L\), then \(pH = 7\) (neutral), if \([H^{+}]>1\times10^{-7}\space mol/L\), \(pH<7\) (acidic), and if \([H^{+}]<1\times10^{-7}\space mol/L\), \(pH > 7\) (alkaline).
d. A buffer is a solution that resists changes in \(pH\) when small amounts of acid or base are added. It usually consists of a weak acid and its conjugate base (e.g., \(CH_{3}COOH\) and \(CH_{3}COO^{-}\)) or a weak base and its conjugate acid.

Answer:

a. An acid is a substance that donates hydrogen ions (\(H^{+}\)).
b. A base is a substance that accepts hydrogen ions (\(H^{+}\)).
c. \(pH\) is a measure of the acidity or alkalinity of a solution, calculated as \(pH =-\log[H^{+}]\).
d. A buffer is a solution that resists changes in \(pH\) when small amounts of acid or base are added.