0

Dyes and pigments - class-IX

Description: dyes and pigments
Number of Questions: 38
Created by:
Tags: chemistry applied chemistry chemistry in daily life
Attempted 0/38 Correct 0 Score 0

Different dyes are used for dyeing different materials. Which of the following statements is false?

  1. Nylon can be dyed with acid dyes

  2. Cotton can be directly dyed with malachite green

  3. Terylene is mainly dyed with disperse dyes

  4. Polyacrylonitrile can be dyed with basic dyes


Correct Option: B
Explanation:

The color of the wool cloth dyed directly by dipping in hot solution of malachite green dye is fast. The color of cotton cloth dyed directly (without using mordant) by dipping in hot solution malachite green is not fast to washing and is of low intensity.

Statement: Tannic acid is a Mordant.

State whether the given statement is true or false.

  1. True

  2. False


Correct Option: A
Explanation:

 Tannic acid is used to mordant cellulose fibres and fabrics before the alum mordant. Many dyestuffs contain tannin (black oak, pomegranate, cutch, fustic, etc) and do not need an additional tannin mordant. Tannins can be clear or they can add colour to the fibre


Hence, the correct option is $true$

Example of basic dye is:

  1. alizarin

  2. indigo

  3. martius yellow

  4. malachite green


Correct Option: A
Explanation:

Basic dye is a stain that is cationic (+ve charged) and so will react with material that is (-ve) negatively charged. Alizarin prominent red dye is a basic dye. Some other examples of basic dyes are methylene blue, crystal violet, basic fuchsin safranin.

 Which of these statements is true about the colorfastness of dyes?

  1. If a dye is fast on one type of fiber it will be fast on all kind of fabrics

  2. If a dye is fast to light, it will also be fast to washing

  3. There are no standardized methods of testing colorfastness for dyes

  4. Wool is the most easily dyed fiber and the resulting color will change the least


Correct Option: D
Explanation:

 Colour fastness is a professional word used in theprocess of dyeing for textile materials that characterize a material's color resistance to fading or running. The term is generally used for clothes. In different veryties of cloth, wool is the most easily dyed fiber and the resulting color will change the least. 

Alizarin belongs to the class of:

  1. vat dyes

  2. mordant dyes

  3. substantive dyes

  4. reactive dyes


Correct Option: B
Explanation:
Alizarin belongs to the mordant type of dyes. It is a red dye originally obtained from the root of the common madder plant, Rubia tinctorum, in which it occurs combined with the sugars xylose and glucose.

It is mainly used in biological research. It stains free calcium and certain calcium compounds with a red or light purple color.

Colloidal solutions are classified on the basis of:

  1. molecular size

  2. organic or inorganic

  3. surface tension value

  4. pH value


Correct Option: A

If a solid is dispersed in a liquid, the colloid is known as:

  1. gel

  2. sol

  3. emulsion

  4. none of the above


Correct Option: B
Explanation:

Sol is a colloidal suspension with solid particles as dispersed phase dissolve in a liquid i.e dispersion medium.

Gel are a dispersion of molecules of a liquid within a solid in which liquid particles are dispersed in the solid medium.
An emulsion is a mixture of two or more liquids that are normally immiscible.
Hence answer is option B

Which of the following is an azo dye?

  1. Methyl orange

  2. Phenolphthalein

  3. Malachite green

  4. Methylene blue


Correct Option: A
Explanation:

Methyl orange is the azo dye, which consists of azo $(-N=N-)$ structure in it. The other compounds do not contain this azo structure in them.

Which of the following is an example of a basic dye? 

  1. Alizarin

  2. Malachite

  3. Indigo

  4. Orange-1


Correct Option: B
Explanation:

All other dyes are natural dyes. Basic dyes are water soluble and are cationic and act as bases. Malachite green is an organic compound. Malachite green is prepared by condensation of  benzaldehyde and dimethylaniline. Basic dyes display cationic functional groups like $-NR _3^+$ or $=NR _2^+$.

Adsorption is multilayer in case of:

  1. physical adsorption

  2. chemisorption

  3. both 

  4. none of the above


Correct Option: A
Explanation:

Adsorption is multilayer in case of physical adsorption. However, in the case of chemisorption, the absorption is unilayer as it involves the formation of a chemical bond between adsorbate and adsorbent molecules.


Hence, option A is correct.

Tyndall effect would be observed in:

  1. solution

  2. solvent

  3. precipitate

  4. colloidal sol


Correct Option: D
Explanation:

If a homogeneous solution is observed in the direction of light, it appears clear and when it is observed from a direction at right angles to the direction of the light beam, it appears perfectly dark. 


But when a beam of light passes through colloidal solutions, it is scattered, the maximum scattered intensity being in the plane at right angles to the path of light. The path beam becomes visible. The effect was first observed by Faraday but was studied in detail by Tyndall and the effect is not commonly known as the Tyndall effect.

Hence, option D is correct.

Auxochromes of dyes generally called as ________.

  1. Color intensifiers

  2. Color depressors

  3. A and B

  4. None of the above


Correct Option: A
Explanation:

Auxochromes are commonly called as color helpers or color intensifiers. Dyes containing auxochromes are basically aromatic compounds and include the presence of aryl rings which have delocalized electron systems. These are responsible for the absorption of different radiations with different wavelengths based on the energy of the electron. If an auxochrome is present in the meta position of the chromophore, then there is no change in the color. Electrons present in the chromophore get excited from the ground level to the excited state.

When visible light falls on them. Chromophores also alter the energy in
the delocalized systems. A chromophore gives the dye the property of absorbing different radiations whereas auxochrome imparts it with the property of being colored.
Hence option A is correct.

Vat dyes are essentially incapable of dyeing:

  1. fiber

  2. stone

  3. wood

  4. none of the above


Correct Option: A,B
Explanation:

Vat dyes are essentially insoluble in water and incapable of dyeing fibers directly. However, reduction in alkaline liquor produces the water-soluble alkali metal salt of the dye, which, in this leuco form, has an affinity for the textile fiber. Subsequent oxidation reforms the original insoluble dye. The color of denim is due to indigo, the original vat dye.

Hence option A Is correct.









An auxochrome is a group of atoms which will impart a particular color when
attached to a_________.

  1. chromophore

  2. chlorophyll

  3. autochrome

  4. none of the above


Correct Option: A
Explanation:

Auxochrome is a Greek word arising from; Auxo meaning to increase and chrome meaning color. An auxochrome is a group of atoms which will impart a particular color when attached to a chromophore but when present alone, will fail to produce that color.
Chromophore is that part of the molecule which when exposed to visible
light will absorb and reflect a certain color.
Hence option A is correct.

Which of the following increases the intensity of the color  of the dye?

  1. Chromophore

  2. Auxochrome

  3. Chlorophyll

  4. Autochrome


Correct Option: A
Explanation:

Auxochrome is a Greek word arising from two-word roots; Auxo meaning to
increase and chrome meaning color. An auxochrome is a group of atoms
which will impart a particular color when attached to a
chromophore but when present alone, will fail to produce that color.

A chromophore is that part of the molecule which when exposed to visible light will absorb and reflect a certain color. Auxochrome increases the color of any organic substance.
Hence option B is correct.

___________is the part of the dye molecule which when exposed to light will absorb and reflect a certain color.

  1. Chromophore

  2. Auxochrome

  3. Autochrome

  4. None of the above


Correct Option: A
Explanation:

Auxochrome is a Greek word arising from two-word roots; Auxo meaning to
increase and chrome meaning color. An auxochrome is a group of atoms
which will impart a particular color when attached to a chromophore but when present alone, will fail to produce that color.

The chromophore is that part of the molecule which when exposed to visible
light will absorb and reflect a certain color.
Hence option A is correct.

Dispersed dyes were originally developed for the dyeing of:

  1. cellulose acetate

  2. cellulose nitrate

  3. A and B both

  4. cellulose amine


Correct Option: A
Explanation:

Dispersed dyes were originally developed for the dyeing of Cellulose acetate and are water-insoluble. The dyes are finely ground in the presence of a dispersing agent and sold as a paste, or spray-dried and sold as a powder.
Hence option A is correct.

The auxochrome part  of a dye:

  1. Is the color producing group of the dye chemical.

  2. Influences the intensity of the dye.

  3. Acts as a mordant.

  4. None of the above


Correct Option: B
Explanation:

An auxochrome (Greek auxnein: "to increase" and chrma: "colour") is a group of atoms attached to a chromophore which modifies the ability of that chromophore to absorb light. They themselves fail to produce the colour; but when present along with the chromophores in an organic compound intensifies the colour of the chromogen.[1] Examples include the hydroxyl group (-OH), the amino group (-NH2), the aldehyde group (-CHO), and the methyl mercaptan group (-SMe).[2]


 An auxochrome is a functional group with nonbonded electrons when attached to the chromophore, changes both the wavelength and intensity of absorption. If these groups are in direct conjugation with the pi-electron system of the chromophore, they may increase the wavelength of light
that  is being absorbed and as a result,t intensify the absorption. A feature of these auxochromes is the presence of at least one lone pair of electrons which can be viewed as extending the conjugated system by resonance.

Hence option B is correct.

The difference between a dye and a pigment is that a dye:

  1. is held to the surface of the fiber by a resin.

  2. is an inorganic chemical that permeates fibers..

  3. usually diffuses into the interior of a fiber from a water solution.

  4. lays on the surface of the fiber.


Correct Option: C
Explanation:

A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution and may require a mordant to improve the fastness of the dye on the fiber.
Hence option C is correct.

Basic dyes are ________.

  1. water-soluble anionic dyes

  2. water-insoluble anionic dyes

  3. water-insoluble cationic dyes

  4. water-soluble cationic dyes


Correct Option: D
Explanation:

Basic dyes are water-soluble cationic dyes that are mainly applied to acrylic fibres but find some use for wool and silk. Usually acetic
acid is added to the dye bath to help the uptake of the dye onto the fiber.
Basic dyes are also used in the coloration of paper.
Hence option D is correct.

Which type of dyes are not used to dye nylon and polyester fibres?

  1. Vat dyes

  2. Basic dyes

  3. Disperse dyes

  4. Insoluble azo dyes


Correct Option: A
Explanation:

Vat dyes are not used to dye nylon and polyester fibres but used to dye cotton fibres


Basic dyes disperse dyes and insoluble azo dyes are used to dye nylon and polyesters.

If  greater the number the double bonds in the carotenoid dyes is more :

  1. the more water soluble it is

  2. the more non-water insoluble it is

  3. the more intense or darker the pigment will be

  4. the weaker the dye color will be


Correct Option: C
Explanation:

If more number of double bonds are present in the carotenoid system the intensity or the darkness of the pigment will increases.
Hence option C is correct.

Which of the following are natural dyes:

  1. alizarin, carminic acid and tartrazine

  2. indigo, bixin and alizarin

  3. tartrazine, FD&C Blue #1, and indigo

  4. chlorophyll, yellow #6 and haematin


Correct Option: B
Explanation:

Natural dyes are dyes derived from animal or plant material without any chemical treatment. They are obtained from sources like flowers,
leaves, insects, bark roots etc.; however, they are not readily
available and involve an extraction process.In th above question and the natural dyes are indigo, bixin and alizarin.
Hence option B is correct.

Which of the following is the characteristic property of a vat dye

  1. must be reduced to a soluble form so that it can dissolve in the dye bath and get Be trapped in the cellulose fiber.

  2. penetrates both the outer ring and the inner core of a piece of fiber.

  3. Remains in its soluble form inside the denim fabric.

  4. Must be in an insoluble form so that it can get trapped in the cellulose fiber.


Correct Option: D
Explanation:

Vat dyes are essentially insoluble in water and incapable of dyeing fibers
directly. However, reduction in alkaline liquor produces the water-soluble
alkali metal salt of the dye, which, in this leuco form, has an affinity for
the textile fiber. Subsequent oxidation reforms the original insoluble dye. The
color of denim is due to indigo, the original vat dye
So a vat dye must be reduced to a soluble form so that it can dissolve in the dye bath and get trapped in the cellulose fiber.
Hence option D is correct

Match metal ion (Part I) with colour (Part II) in presence of alizarin:


  Part I   Part II
I. ${ Sn }^{ 2+ }$ A. Blue
II. ${ Mg }^{ 2+ }$ B. Pink
III. ${ Al }^{ 3+ }$ C. Violet
IV. ${ Ba }^{ 2+ }$ D. Red

  1. I-A II-D III-C IV-B

  2. I-B II-A III-D IV-C

  3. I-C II-B III-A IV-D

  4. I-D II-C III-B IV-A


Correct Option: B
Explanation:
$Alizarin$ is a typical mordant dye gives different colours with metal ions as some of them are given below: 

$Al^{3+} \Rightarrow Red$
$Sn^{2+}  \Rightarrow Pink$
$Ba^{2+} \Rightarrow Voilet$
$Mg^{2+} \Rightarrow Blue$

Option B is correct.

The Mordant is:

  1. a dye color that bites into the fiber.

  2. a metallic ion that attaches to fibers and causes a color emission.
    a chemical that stops the dye process.

  3. a metallic ion or salt added to the dye bath to make dyes less colorfast by forming a bridge between the dye and the fiber.

  4. None of these


Correct Option: C
Explanation:

A mordant or dye fixative is a substance used to set dyes on fabrics or tissue sections by forming a coordination complex with the dye which is then attached to the fabric or tissue.

[1] It may be used for dyeing fabrics, or for intensifying stains in a cell or tissue preparations. 
it was thought that a mordant helped the dye bite onto the fibre so that it
would hold fast during washing. A mordant is often a polyvalent metal ion.

[2] The resulting coordination complex of dye and ion is colloidal and can be either acidic or alkaline. So a mordant is a metallic ion or salt added to the dye bath to make dyes more colourfast by forming a bridge between the dye and the fibre.

Hence option D is correct.

Dyes in litmus are made from:

  1. mycorrhizae

  2. rhizoids

  3. lichens

  4. algae


Correct Option: C
Explanation:
A water-soluble mixture which is a combination of different type of dyes which are extracted from lichens is known as litmus. This litmus is absorbed on filter paper to made one form of pH indicator, used to test the acidity or basicity of substances. 

If  greater the number the double bonds in the carotenoid dyes is more :

  1. The more water soluble it is.

  2. The more non-water insoluble it is.

  3. The more intense or darker the pigment will be.

  4. The weaker the dye color will be.


Correct Option: C
Explanation:

If more number of double bonds are present in the carotenoid system the intensity or the darkness of the pigment will increases.
Hence option C is correct.

The first dye that was prepared synthetically was:

  1. Mauveine

  2. Azo-dyes

  3. Malachite green

  4. Phthalein dyes


Correct Option: A
Explanation:

(A) Mauveine

Mauveine, also known as aniline purple and Perkin's mauve, was the first synthetic dye. It was discovered serendipitously by William Henry Perkin in 1856. It is also among the first dyes to have been mass-produced.

The chemical part of the dye that absorbs light and produces colour is called a :

  1. natural pigment

  2. chromophore

  3. neon

  4. photochrome


Correct Option: B
Explanation:
A chromophore is a group of atoms which control the colour of the dye. Thus option B is the correct answer.

A colloidal solution can be purified by following the method of:

  1. dialysis

  2. peptization

  3. filtration

  4. oxidation


Correct Option: A
Explanation:

A colloidal solution can be purified by the following methods - Dialysis, Electro-dialysis and Ultrafiltration.

Hence, option A is the correct answer.

What is the basic difference between dye and pigment?

  1. Dye is an inorganic chemical that permeates fibers

  2. Dye is held to the surface of the fiber by a resin

  3. Dye diffuses into the interior of a fiber from a water solution

  4. Dyes lays on the surface of the fiber


Correct Option: C
Explanation:

The dye is known as a coloured substance which has a great affinity towards the substrate on which it is applied. The basic difference in between dye and pigment is that dye is diffused into the interior of a given fabric from its water solution whereas pigment does not.

The dyes used in reduced state and are then oxidized in the fabric by air are called:

  1. azo dye

  2. vat dye

  3. basic dye

  4. dispersed dye


Correct Option: B
Explanation:

Vat dyes can applied directly on fibre and are generally insoluble in water. These can be used only on cotton but can not be used on silk and wool. In this case  dying is a continuous process and is carried out in a large vessel called vat. For this reason these dyes are Known as vat dyes, indigo is an example of vat dyes 

When a dye is formed on the fiber or cloth by a chemical reaction at the time of dyeing, the process is known as:

  1. synthesis

  2. direct dyeing

  3. vat dyeing

  4. absorption


Correct Option: B
Explanation:

Direct Dye is a class of dyestuff's that are applied directly to the substrate in a neutral or alkaline bath. They produce full shades on cotton and linen without mordant and can also be applied to rayon, silk, and wool. Direct dyes give bright shades but exhibit poor wash fastness. Various after treatments are used to improve the wash fastness of direct dyes, and such dyes are referred to as 'after treated direct colors". Direct dyes are molecules that adhere to the fabric molecules without help from other chemicals.

Indigo dye is an example of :

  1. Azo dye

  2. Vat dye

  3. Dispersed dye

  4. Basic dye


Correct Option: B
Explanation:

 Indigo dye is an example of Vat dye, These dyes can be used only on cotton it is a long continuous process which is carried out in a large vessel known as Vat. These dyes are applied directly on the fibre and are generally insoluble in water.

Which of the following is not a natural dye of either vegetable or animal origin?

  1. Tyrian purple

  2. Indigo

  3. Saffron

  4. Azo dye


Correct Option: D
Explanation:

Azo dyes are organic compounds, which contain the coloring azo function (N=M-). The azo function is often bound to an aromatic ring, and the dye can then be broken down to an aromatic amine, arylamine. This can take place either chemically, through reductive cleavage, or through the body's own enzyme system. Some azo dyes can also be broken down to arylamines during storage due to light and high temperature. Some arylamines have been judged to be carcinogenic.

When soap or detergent is added to water, which of the following is true?

  1. This results in formation of oil in water type emulsion.

  2. This results in formation of water in oil type emulsion.

  3. This results in formation of either oil in water type emulsion or water in oil type emulsion.

  4. No emulsion is formed.


Correct Option: A
Explanation:

When soap or detergent is added to water, this results in the formation of oil in water type emulsion.
The polar water-soluble ( hydrophilic) head is on the surface of the micelle whereas non-polar oil soluble (hydrophobic) tail is in the centre of the micelle. In the centre of the micelle, small oil droplets are present in which hydrophobic part of micelle dissolves.

In coloured photography, the colour film is developed by oxidation of the developer and then reacting with:

  1. an alkai to form a salt

  2. a coupler to form a dye

  3. an acid to form a salt

  4. a metal to form a pigment


Correct Option: B
Explanation:

The development step uses reducing chemicals, and the exposed silver-halide grains develop to pure silver. The oxidized developer is produced in this reaction, and the oxidized developer reacts with chemicals called couplers in each of the image-forming layers. This reaction causes the coupler to form a color, and this color varies depending on how the silver-halide grains were spectrally sensitized. A different color-forming coupler is used in the red, green, and blue sensitive layers. The latent image in the different layers forms a different colored dye when the film is developed.

- Hide questions