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# (A) Explain Bragg’s spectrometer method.(B) Write about the preparation of colloids by chemical methods.

Last updated date: 23rd Jul 2024
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Hint:A.X-rays are electromagnetic radiations which have high energy and can pass through various objects. Bragg’s spectrometer method is a method used for the study of crystals with help of X-ray radiations.
B.A colloid refers to a mixture of particles with different radius but the solution has an evenly distributed concentration. These colloidal solutions can be prepared with the help of various chemical reactions.

A.Bragg’s spectrometer method.
X-rays are electromagnetic radiations which have high energy and can pass through various objects like the human body to generate images of tissues. This helps to detect the problems related to human bones and joints. A prolonged exposure to high radiation levels of X-rays may cause vomiting, fainting, hair loss and poses a slight risk of cancer. X-ray spectroscopy is referred to as the measure of change in energy levels and helps to understand interactions between atoms of various materials.
Bragg’s spectrometer method is a method used for the study of crystals with help of X-ray radiations. It measures the scattering angles of crystals which help to determine the structure of the crystals. This process of determining the structure of crystal with the help of X-ray is known as crystallography. The apparatus includes a rotation table on which the crystal is placed with a scale. A narrow beam of X-ray falls on the crystal from an X-ray tube. The intensity of the reflected beam measures the ionization of the crystal. The Bragg’s angle is the small angle formed between the incident X-ray and the diffracting planes of a crystal. This is stated under Bragg's law which is represented as $n\lambda = 2d\sin \theta$ where $d$ is the distance and $\theta$ is the reflected angle.
B.Preparation of colloids by chemical methods.
A colloid refers to a mixture of particles with different radius but the solution has an evenly distributed concentration. Hydrophilic colloidal solutions are prepared by various chemical reactions which involve the following:
Oxidation: ${H_2}S$ is passed in a solution of $S{O_2}$ to obtain a colloidal solution of sulphur.
$2{H_2}S + S{O_2} \to 2{H_2}O + 3S$
Reduction: Reducing agents like tannic acid reacts with solutions of silver nitrate or gold chloride to reduce them to silver sol and gold sol.
Double decomposition: A yellow coloured sol of arsenic sulphide is obtained by passing a stream of hydrogen sulphide through a cold solution of arsenious oxide. The excess hydrogen sulphide gas is removed by hydrogen.
$A{s_2}{O_3} + 3{H_2}S \to A{s_2}{S_3} + 3{H_2}O$
Hydrolysis: Hydrolysis of salts gives the colloidal solutions of hydroxides of various elements like $Fe,Cr,Al$ and others.
$FeC{l_3} + 3{H_2}O \to Fe{(OH)_3} + 3HCl$

Note:
Natural colloids such as blood, plasma and others provide proteins like antibodies and albumin. Colloids are used for manufacturing paints and inks and are also used as a thickening agent in various industrial products like coatings, toothpaste and lubricants.