The vapour density of a metal chloride is \(85 .\) If equivalent weight of metal is \(7.01\), calculate the at.wt. of metal.

Molar mass is a fundamental concept in chemistry that refers to the mass of one mole (approximately 6.022 x 10²³ particles) of a substance. The units for molar mass are grams per mole (g/mol). It is a critical value used to convert between the mass of a substance and the amount in moles, facilitating stoichiometric calculations in chemical reactions.

Molar mass can be determined by summing the atomic masses of all atoms in a formula unit of a compound. For instance, for a simple compound like carbon dioxide (CO₂), the molar mass is the sum of one carbon atom's mass and two oxygen atoms' masses. This concept lets us understand the proportions of elements in a compound, which is crucial when addressing vapor density problems.

The equivalent weight of a substance is a throwback to earlier days in chemistry, but it's still useful in some contexts. It represents the mass of a substance that will combine with or replace a standard amount of another substance. In the context of acids and bases, it is the mass that supplies or reacts with one mole of hydrogen ions (H⁺) or hydroxide ions (OH^-).

For metals, the equivalent weight is the atomic weight divided by the valency (also referred to as the combining power of the metal). Understanding the equivalent weight is essential in the field of electrochemistry and when dealing with redox reactions.

Atomic weight, also known as atomic mass, is the average mass of atoms of an element, measured in atomic mass units (amu). The calculation takes into account the relative abundance of each isotope of an element. The periodic table lists the atomic weight for each element, which can be used for determining the molar mass of compounds.

In practice, finding the atomic weight directly from vapor density and equivalent weight involves intermediate steps like considering the compound's formula and applying stoichiometry to uncover the individual contributions to the molar mass.

Valency is the measure of an element's ability to combine with other elements. It denotes the number of electrons an atom can lose, gain, or share during a chemical reaction. For simple compounds like metal chlorides, the valency helps us define their chemical formula. For instance, if a metal has a valency of 2, it will combine with two chlorine atoms to form a metal chloride (MCl₂).

Understanding the valency is essential when interpreting chemical formulas and predicting how different elements will react with each other. It helps in solving problems related to chemical reaction equations and is part of the foundation for stoichiometry.

Stoichiometry is one of the most important themes in the field of chemistry. It provides the quantitative relationship between reactants and products in a chemical reaction. In simpler terms, stoichiometry tells us how much of each substance is involved in a reaction.

When we deal with chemical equations, stoichiometry allows us to predict the amounts of products produced from given quantities of reactants and vice versa. This is indispensable for laboratory work where precise amounts of substances are crucial. For vapor density problems, stoichiometry is utilized to relate the mass of the substance to the mole concept, ultimately aiding in the understanding of how a compound’s composition relates to its physical properties.