Explanation

• In a process at constant volume, the change in internal energy (ΔE) is equal to the heat added to the system (q).
• Therefore, at constant volume, ΔE = q.

Explanation

• An atom typically has an equal number of electrons and protons.
• They are equal in number to the atomic number (Z) of the element.
• This number is unique to each element and determines the properties of the element.

Explanation

When alcohol reacts with sodium, it produces alkoxide ions and hydrogen gas.

Explanation

Pyridine is a six-membered ring with nitrogen in its structure, which makes it a heterocyclic compound.

Explanation

Thus, the First law of thermodynamics furnishes the relationship between:

• heat
• work
• the internal energy of the system

Explanation

• Solids like salt (sodium chloride) dissolve in water to form a saltwater mixture or solution.
• When salt is added to water, the salt particles break apart and distribute evenly throughout the water, creating a homogeneous mixture.

Explanation

Matter can change from one form to another through various processes, including:

• Heating: Melting (solid to liquid), Vaporization (liquid to gas)
• Cooling: Freezing (liquid to solid), Condensation (gas to liquid)

For example, ice (solid) can change to water (liquid) by heating, and water (liquid) can change to steam (gas) by further heating.

Similarly, steam (gas) can change to water (liquid) by cooling, and water (liquid) can change to ice (solid) by further cooling.

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

Halogens (Group 17 elements) react with hydrogen gas to form hydrogen halides, also known as hydrogen halogenides.

The reaction is:

• H2 (hydrogen gas) + X2 (halogen gas) → 2HX (hydrogen halide)
• Where X represents the halogen element (e.g., Cl, Br, I, F).

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.