Tag: chemistry

Questions Related to chemistry

Select the correct statements about enzymes.
chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

  1. Enzymes arc biological catalysts found in organisms

  2. All enzymes are proteins

  3. Enzymes can catalyse any reaction

  4. Enzymes activity is optimum at $37^o C $

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Correct Option: A,D

Which of the following statements regarding enzyme inhibition is correct -

chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

  1. Competitive inhibition is seen when a substrate competes with an enzyme for
    binding to an inhibitor protein

  2. Non-competitive inhibitors often bind to the
    enzyme irreversibly

  3. Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme

  4. Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate

Show answer
Correct Option: C
Explanation:
Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme because competitive inhibitor has a similar structure as that of a substrate, so it blocks the active site of an enzyme thereby reducing the production formation.

Enzymes, which catalyze biochemical reactions are very complex. They help in the reaction of very specific substances. This suggests that the enzyme and the reacting biochemicals are complementary to one another like a:

chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

  1. dog in his kennel

  2. horse and a rider

  3. lock and key

  4. leaf and a bud

Show answer
Correct Option: C
Explanation:

Enzymes are very specific in nature. Only those substrates that can fit into the active site of an enzyme can be bound within it. This specific action is similar to a lock and key where a key(reacting biochemicals) can only be used to actuate a specific lock(enzyme) and not all of them. 

Which of the following factors are responsible for the increase in the rate of a surface catalysed reaction?
I. A catalyst provides proper orientation for the reactant molecules to react
II. Heat of adsorption of reactants on a catalyst helps reactant molecules to.overcome activation energy
III. The catalyst increases the activation energy of the reaction 
IV. Adsorption increases the local concentration of reactant molecules on the surface of the catalyst
Select the correct answer using the codes given below:

chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

  1. I and II

  2. I and III

  3. I, II and IV

  4. I, II and III

Show answer
Correct Option: A
Explanation:

A catalyst works by providing an alternative reaction pathway to the reaction product. The rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.

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

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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

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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