# Gravimetric Analysis

Gravimetric analysis: In gravimetric analysis we relate the weights of two substances or a weight of a substance with a volume of a gas or volumes of two or more gases.

## Problems Involving Mass-Mass Relationship

Proceed for solving such problems according to the following instructions,

(i) Write down the balanced equation to represent the chemical change.

(ii) Write the number of moles below the formula of the reactants and products. Also write the relative weights of the reactants and products (calculated from the respective molecular formula), below the respective formula.

(iii) Apply the unitary method to calculate the unknown factor (s).

Problems Involving Mass-Volume Relationship

For solving problems involving mass-volume relationship, proceed according to the following instructions,

(i) Write down the relevant balanced chemical equations (s).

(ii) Write the weights of various solid reactants and products.

(iii) Gases are usually expressed in terms of volumes. In case the volume of the gas is measured at room temperature and pressure (or under conditions other than N.T.P.), convert it into N.T.P. by applying gas equation.

(iv) Volume of a gas at any temperature and pressure can be converted into its weight and vice-versa with the help of the relation, by (PV = g/M)×RT where g is weight of gas, m is mole. wt. of gas, R is gas constant.

Calculate the unknown factor by unitary method.

## Problems Based on Volume-Volume Relationship

Such problems can be solved according to chemical equation as,

(i) Write down the relevant balanced chemical equation.

(ii) Write down the volume of reactants and products below the formula to each reactant and product with the help of the fact that 1m molecule of every gaseous substance occupies 22.4 litres at N.T.P.

(iii) In case volume of the gas is measured under particular (or room) temperature, convert it to volume at NTP by using ideal gas equation.

Take the help of Avogadro’s hypothesis “Equal volume of different gases under the similar conditions of temperature and pressure contain the same number of molecules”.