Tag: applied chemistry
Questions Related to applied chemistry
The auxochrome part of a dye:
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Is the color producing group of the dye chemical.
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Influences the intensity of the dye.
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Acts as a mordant.
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None of the above
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:
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is held to the surface of the fiber by a resin.
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is an inorganic chemical that permeates fibers..
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usually diffuses into the interior of a fiber from a water solution.
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lays on the surface of the fiber.
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 ________.
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water-soluble anionic dyes
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water-insoluble anionic dyes
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water-insoluble cationic dyes
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water-soluble cationic dyes
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?
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Vat dyes
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Basic dyes
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Disperse dyes
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Insoluble azo dyes
Vat dyes are not used to dye nylon and polyester fibres but used to dye cotton fibres.
If greater the number the double bonds in the carotenoid dyes is more :
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the more water soluble it is
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the more non-water insoluble it is
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the more intense or darker the pigment will be
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the weaker the dye color will be
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:
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alizarin, carminic acid and tartrazine
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indigo, bixin and alizarin
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tartrazine, FD&C Blue #1, and indigo
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chlorophyll, yellow #6 and haematin
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
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must be reduced to a soluble form so that it can dissolve in the dye bath and get Be trapped in the cellulose fiber.
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penetrates both the outer ring and the inner core of a piece of fiber.
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Remains in its soluble form inside the denim fabric.
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Must be in an insoluble form so that it can get trapped in the cellulose fiber.
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 |
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I-A II-D III-C IV-B
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I-B II-A III-D IV-C
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I-C II-B III-A IV-D
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I-D II-C III-B IV-A
$Sn^{2+} \Rightarrow Pink$
$Mg^{2+} \Rightarrow Blue$
Option B is correct.
The Mordant is:
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a dye color that bites into the fiber.
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a metallic ion that attaches to fibers and causes a color emission.
a chemical that stops the dye process. -
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.
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None of these
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:
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mycorrhizae
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rhizoids
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lichens
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algae