Acid | MCQs

Explanation

A litmus test is a phrase that originated from the use of litmus paper in chemistry, which changes color in response to certain conditions.

In a broader sense, a litmus test refers to a situation, event, or factor that clearly indicates whether a particular approach, idea, or decision is effective, valid, or acceptable.

It's a decisive test that provides clear evidence or proof.

Explanation

• pH is a measure of the concentration of hydrogen ions (H+) in an aqueous solution.
• The term "pH" was coined by the Danish chemist Søren Sørensen in 1909, and it stands for "power of hydrogen". It is defined as the negative logarithm of the concentration of hydrogen ions in a solution: pH = -log[H+]
• A pH of 7 is neutral, while values below 7 are acidic and above 7 are basic.

Explanation

• A buffer solution is a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid, that resists changes in pH when an acid or base is added to it.
• This is because the acid and its conjugate base (or the base and its conjugate acid) react with the added acid or base to maintain the equilibrium, keeping the pH constant.

Explanation

The pH of a buffer solution depends on the concentration of both the acid (H+) and its conjugate base (-OH-). A buffer solution is a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid. The pH of the solution is determined by the ratio of the concentrations of the acid and its conjugate base, as described by the Henderson-Hasselbalch equation: pH = pKa + log([base]/[acid])

Where:

• pH is the negative logarithm of the hydrogen ion concentration
• pKa is the acid dissociation constant
• [base] is the concentration of the conjugate base
• [acid] is the concentration of the acid

Therefore, the pH of a buffer solution depends on the concentration of both the acid (H+) and its conjugate base (-OH-).

Explanation

• The new classification of acid and base, based on the description of the proton, was given by Johannes Brønsted and Thomas Lowry.
• They defined an acid as a compound that donates a proton (H+) and a base as a compound that accepts a proton.
• This definition is broader than the Arrhenius definition, which is limited to aqueous solutions, and it has been widely accepted and used in chemistry.

Explanation

Lime water when used with butter to form butyric acid can cure acidity.

The butyric acid is acidic.

The lime water (soluble form of calcium hydroxide) is basic.

Acid & base mix & become neutral which cures the acidity

Explanation

• If urea reacts with ammonia according to the Lowry and Bronsted theory, it acts as an acid to form a neutral compound.
• In the reaction between urea (H₂NCONH₂) and ammonia (NH₃), urea donates a proton (H⁺) to ammonia, turning it into the ammonium ion (NH₄⁺) and urea into its conjugate acid (HNCONH₂⁺).

Explanation

The salt which is formed by neutralization of weak acid and weak base is (NH4)2CO3.

Explanation

The alkaline mucus secreted by the Cowper's glands also plays an important role in neutralizing the acidic nature in the urine.

Explanation

Bases are any substances that produce hydroxide ions when dissolved in water (OH–).

while

acid is any substance that ionizes when it dissolves in water to give the H+