Tag: dyes

Questions Related to dyes

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

dyes dyes and pigments chemistry in daily life applied chemistry chemistry

  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

Show answer
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.

dyes dyes and pigments chemistry in daily life applied chemistry chemistry

  1. True

  2. False

Show answer
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:

dyes dyes and pigments chemistry in daily life applied chemistry chemistry

  1. alizarin

  2. indigo

  3. martius yellow

  4. malachite green

Show answer
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?

dyes dyes and pigments chemistry in daily life applied chemistry chemistry

  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

Show answer
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:

dyes dyes and pigments chemistry in daily life applied chemistry chemistry

  1. vat dyes

  2. mordant dyes

  3. substantive dyes

  4. reactive dyes

Show answer
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:

dyes dyes and pigments chemistry in daily life applied chemistry chemistry

  1. molecular size

  2. organic or inorganic

  3. surface tension value

  4. pH value

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Correct Option: A

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

dyes dyes and pigments chemistry in daily life applied chemistry chemistry

  1. gel

  2. sol

  3. emulsion

  4. none of the above

Show answer
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?

dyes dyes and pigments chemistry in daily life applied chemistry chemistry

  1. Methyl orange

  2. Phenolphthalein

  3. Malachite green

  4. Methylene blue

Show answer
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? 

dyes dyes and pigments chemistry in daily life applied chemistry chemistry

  1. Alizarin

  2. Malachite

  3. Indigo

  4. Orange-1

Show answer
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:

dyes dyes and pigments chemistry in daily life applied chemistry chemistry

  1. physical adsorption

  2. chemisorption

  3. both 

  4. none of the above

Show answer
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.