What do you mean by activity and selectivity of catalysts?
Important features of solid catalyst:
(a) Activity: The activity of a catalyst is its ability to accelerate chemical reactions. It depends upon the strength of chemisorption to a large extent.
The catalytic activity of a metal for hydrogenation increases as we move from Group 5 metals to Group 11. The maximum activity is shown by metals of Groups 7, 8 and 9.
(b) Selectivity: The selectivity of a catalyst is its ability to direct a reaction to yield a particular product. It mean a substance which acts as a catalyst in one reaction may not act as a catalyst in other reaction e.g., we get different products when we use different catalysts in the reaction between H2 and CO.
Explain what is observed
(i) when a beam of light is passed through a colloidal sol.
(ii) an electrolyte, NaCI is added to hydrated ferric oxide sol.
(iii) electric current is passed through a colloidal sol.
Assertion (A): Colloidal solutions show colligative properties.
Reason (R): Colloidal particles are large in size.
A colloid is formed by adding FeCl3 in excess of hot water. What will happen if excess sodium chloride is added to this colloid?
Distinguish between the meaning of the terms adsorption and absorption. Give one example of each.
What type of solutions are formed on dissolving different concentrations of soap in water?
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the following choices:
(a) Both Assertion and Reason are correct and the Reason is the correct explanation for Assertion.
(b) Both Assertion and Reason arc correct but Reason is not the correct explanation for Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Both Assertion and Reason are incorrect.
(e) Assertion is incorrect but Reason is correct
Assertion (A): An ordinary filter paper impregnated with collodion solution stops the flow of colloidal particles.
Reason (R): Pore size of the filter paper becomes more than size of colloidal particle.
Why is it essential to wash the precipitate with water before estimating it quantitatively?
Give an example where physisorption changes to chemisorption with rise in temperature. Explain the reason for change.
Match the types of colloidal systems given in Column I with the name given in Column II.
Method of formation of solution is given in Column I. Match it with the type of solution given in Column II.
What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated?
What do you understand by shape selective catalysis? Why are zeolites good shape selective catalysts?
Assertion (A): Colloidal solutions do not show Brownian motion.
Reason (R): Brownian motion is responsible for stability of sols.
Assertion (A): Detergents with low CMC are more economical to use. Reason (R): Cleansing action of detergents involves the formation of micelles. These are formed when the concentration of detergents becomes equal to CMC.
Arrange the following diagrams in correct sequence of steps involved in the mechanism of catalysis, in accordance with modem adsorption theory.
Why does the white precipitate of silver halide become coloured in the presence of dye eosin.
What is the role of adsorption in froth floatation process used especially for concentration of sulphide ores?
Which of the following statements are correct about solid catalyst?
(a) Same reactants may give different product by using different catalysts.
(b) Catalyst does not change AH of reaction.
(c) Catalyst is required in large quantities to catalyse reactions.
(d) Catalytic activity of a solid catalyst does not depend upon the strength of chemisorption.
Which of the following statements are correct?
(a) Mixing two oppositely charged sols neutralizes their charges and stabilizes the colloid.
(b) Presence of equal and similar charges on colloidal particles provides stability to the colloids.
(c) Any amount of dispersed liquid can be added to emulsion without destabilizing it.
(d) Brownian movement stabilizes sols.
