Tag: chemistry

Questions Related to chemistry

Which of the following statement(s) is/are correct?

chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

  1. Primary valency of the central metal of a complex is always satisfied by anions.

  2. Secondary valency of the central metal of a complex may be satisfied by either negative ions or neutral molecules.

  3. Species which show primary valencies in a complex compound can be precipitated out.

  4. None of the above

Show answer
Correct Option: A,B,C
Explanation:

In short the Werner's theory may be stated as follows:

  1. The central metal in a complex possesses two types of valencies, primary or ionizable valency and secondary valency or non-ionizable valency.
  2. While the primary valency of the metal is variable, the secondary valency has a fixed value. The primary valency refers to the oxidation state and the secondary valency to the coordination number of the metal.
  3. The primary valency is satisfied by only negative ions whereas the secondary valency either by anions or neutral molecules or both.
  4. The secondary valencies are directed in space towards fixed positions around the neutral atom.
Hence, options A, B and C are correct.

When $AgNO _3$ is added to a solution of $Co(NH _3) _5 Cl _3$, the precipitate of $AgCl$ shows two ionized chloride ions. This means:

chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

  1. only two chlorine atoms satisfy primary valency and one secondary valency

  2. one chlorine atom satisfies primary as well as secondary valency

  3. two chlorine atoms satisfy primary valency

  4. three chlorine atoms satisfy secondary valency

Show answer
Correct Option: B,C
Explanation:

Option (B),(C) are correct.
When $AgNO _3$ is added to a solution of $Co(NH _3) _5 Cl _3$, the precipitate of $AgCl$ shows two ionized chloride ions.This means one chlorine atom satisfies primary as well as secondary valency and two chlorine atoms satisfy primary valency. Hence, $Co(NH _3) _5 Cl _3$, can be written as $[Co(NH _3) _5 Cl]Cl _2$,

According to the adsorption theory of catalysis, the rate of reaction increases with the use of a catalyst because:

chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

  1. the heat liberated during adsorption increases the rate of reaction

  2. the kinetic energy of reactants increases which increases the rate of reaction

  3. the activation energy of reaction increases which increases the rate of reaction

  4. the concentration of reactants at the active centers becomes high due to adsorption the rate of reaction

Show answer
Correct Option: D
Explanation:

Adsorption theory of Heterogeneous catalysis involves five steps-

  • Diffusion of reactants to the surface of the catalyst.
  • Adsorption of reactant molecules on the surface of the catalyst. (Occurrence of chemical reaction on the catalyst’s surface through formation of an intermediate.
  •  Desorption of reaction products from the catalyst surface, and thereby,  making the surface available again for more reaction to occur.
  •  Diffusion of reaction products away from the catalyst’s surface.
  • So, we can deduce from Adsorption theory of catalysis that as the concentration of reactants at active centers increases due to adsorption and thus the rate of the reaction is also increased.

Match the column I and column II and mark the appropriate choice.

Column I Column II
(A) Diastase (i) Proteins $\rightarrow$ peptones
(B) Pepsin (ii) Glucose $\rightarrow$ ethyl alcohol
(C) Ptyalin (iii) Starch $\rightarrow$ maltose
(D) Zymase (iv) Starch $\rightarrow$ sugar
chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

  1. (A) $\rightarrow$ (iv), (B) $\rightarrow$ (ii), (C) $\rightarrow$ (i), (D) $\rightarrow$ (iii)

  2. (A) $\rightarrow$ (ii), (B) $\rightarrow$ (i), (C) $\rightarrow$ (iv), (D) $\rightarrow$ (iii)

  3. (A) $\rightarrow$ (i), (B) $\rightarrow$ (ii), (C) $\rightarrow$ (iii), (D) $\rightarrow$ (iv)

  4. (A) $\rightarrow$ (iii), (B) $\rightarrow$ (i), (C) $\rightarrow$ (iv), (D) $\rightarrow$ (ii)

Show answer
Correct Option: D
Explanation:

  • Enzymes are macromolecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products. 
Various enzymes which catalyses different convertions are-
  • Diastace converts $Starch\rightarrow maltose$
  • Pepsin converts $Proteins\rightarrow peptones$
  • Ptyalin converts $Starch\rightarrow sugar$
  • Zymase converts $Glucose\rightarrow ethyl alcohol$
  • Invertase converts $Cane sugar\rightarrow Glucose+Fructose$

The activity of an enzyme becomes ineffective:

chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

  1. at low temperature

  2. at atmospheric pressure

  3. at high temperature

  4. in aqueous medium.

Show answer
Correct Option: C
Explanation:

  • Enzymes are macromolecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products. 
Enzyme catalysis is unique in its efficiency and high degree of specificity.
  • Enzymes are Highly specific nature.
  • Enzymes are highly active under optimum temperature.
  • Enzymes are highly active under optimum pH.
  • The activity of enzymes gets increased in presence of activators and co-enzymes.

Which of the following is not correct for enzyme catalysis?

chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

  1. The enzyme activity is maximum at optimum pH which is between 5-7.

  2. Each enzyme is specific for a given reaction.

  3. The favourable temperature range of enzyme activity is between 50-60$^{\circ}$C.

  4. The enzymatic activity is increased in presence of certain substances called co-enzymes.

Show answer
Correct Option: C
Explanation:

  • Enzymes are macromolecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products. 
Enzyme catalysis is unique in its efficiency and high degree of specificity.
  • Enzymes are Highly specific nature.This says that enzyme is specific for a given reaction.
  • Enzymes are highly active under optimum temperature.The optimum temperature range for enzymatic activity is 298-310K.
  • Enzymes are highly active under optimum pH.Optimum pH level is between 5-7.
  • The activity of enzymes gets increased in presence of activators and co-enzymes.

Identify the correct statement regarding enzymes.

chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

  1. Enzymes are specific biological catalysts that possess well defined active sites.

  2. Enzymes are normally heterogeneous catalysts that are very specific in their action.

  3. Enzymes are specific biological catalysts that cannot be poisoned.

  4. Enzymes are specific biological catalysts that can normally function at very high temperature (T=1000K).

Show answer
Correct Option: A
Explanation:

  • Enzyme catalysis is unique in its efficiency and a high degree of specificity.

There are various characteristics are exhibited by enzyme catalysts-
  • Most highly efficient: One molecule of an enzyme may transform one million molecules of the reactant per minute.

  • Highly specific nature: Each enzyme is specific for a given reaction, i.e., one catalyst cannot catalyse more than one reaction. 

  • Highly active under optimum temperature: The rate of an enzyme reaction becomes maximum at a definite temperature, called the optimum temperature.

  • Highly active under optimum pH: The rate of an enzyme-catalysed reaction is maximum at a particular pH called optimum pH, which is between pH values 5-7.

  • Enzymes are normally homogeneous catalysts.

Hence, options A is the correct answers

          Some drugs do not bind the enzyme's active site, instead, bind to a different site of an enzyme. This site is called:

          chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

          1. allosteric site

          2. substrate site

          3. ionic site

          4. competitive site

          Show answer
          Correct Option: A
          Explanation:

          A substance produced by a living organism which acts as a catalyst to bring about a specific biochemical reaction.

          In their catalytic activity, enzymes perform two major functions:

          (i) The first function of an enzyme is to hold the substrate for a chemical
          reaction. Active sites of enzymes hold the substrate molecule in a
          suitable position, so that it can be attacked by the reagent effectively.
          (ii) The second function of an enzyme is to provide functional groups
          that will attack the substrate and carry out chemical reaction.
           Drugs inhibit any of the above mentioned activities of enzymes.
          Drugs inhibit the attachment of substrate on active site of enzymes
          in two different ways;
          (i) Drugs compete with the natural substrate for their attachment
          on the active sites of enzymes. Such drugs are called competitive
          inhibitors.
          (ii) Some drugs do not bind to the enzyme’s active site. These bind to a different site of enzyme which is called allosteric site. This binding of inhibitor at allosteric site changes the shape of the active site in such a way that substrate cannot
          recognise it.

          Determine the surface area of a catalyst that adsorbs $10^3cm^3$ nitrogen at STP per gram in order to form mono layer. The effective area occupied by nitrogen molecule on the surface is $0.1602\times { 10 }^{ -14 }\quad { cm }^{ 2 }$

          chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

          1. $579m^2$

          2. $449 m^2$

          3. $579cm^2$

          4. none of these

          Show answer
          Correct Option: B

          Enzymes in the living systems:

          chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

          1. provide energy

          2. provide immunity

          3. transport oxygen

          4. catalyse biological reactions

          Show answer
          Correct Option: D
          Explanation:

          Enzymes in the living systems catalyse biological reactions. 


          Enzymes speed up the rate of reactions without involving in the reactions. Most enzymes act specifically with only one reactant to produce products. 

          Enzymes also regulates from a state of low activity to high activity and vice versa. They acts as a biocatalyst.

          Option D is correct.