Chemistry Test - 29

Crystalline solids are composed of many small crystals, each of which is called a unit cell. It is a specific term. Monomer is the basic unit for a polymer, and atoms make up molecules, which can further arrange themselves to form solids, liquids or gases.

Kohlrausch's law states that the equivalent conductivity of an electrolyte at infinite dilution is equal to the sum of the conductances of the anions and cations. If salt is dissolved in water, the conductivity of the solution is the sum of the conductances of the anions and cations.

Aspartame is unstable at cooking temperature therefore limited to cold foods and soft drink only.

Concept:

Artificial sweetener: as an alternative to sucrose, some artificial sweetener is used.

• The diabetic patient can’t take sucrose, but this sweetener can be taken.
• It does not take part in biochemical reactions in the body.
• And also don’t produce calories in the body.
• So these are called calorie-free sweeteners.

There are many artificial sweeteners, Major examples of artificial sweeteners are:

1. Saccharin: it is one of the popular sweeteners. the chemical name of saccharine is ortho-sulphonamide. but nowadays its uses are restricted.
2. Aspartame: it is produced from two amino acids – phenylalanine and aspartic acid. It is 200 times sweeter than sucrose. It is used in soft cold drinks.
3. Alitame: it is 2000 times sweeter than that sugar.
4. Sucralose: it is the trichloro derivative of sucrose. it is 600 times sweeter than sucrose.
5. Cyclamate and succinic acid are used as artificial sweeteners.

Concept:

• A catalyst is any material in chemistry that increases the rate of a reaction without being ingested.
• A small amount of the catalyst can catalyse a large amount of reactants.
• A catalyst does not alter Gibbs energy of a reaction.
• It catalyses the spontaneous reactions but does not catalyse non-spontaneous reactions.
• A catalyst does not change the equilibrium constant of a reaction rather, it helps in attaining the equilibrium faster.
• A catalyst is a material that speeds up or slows down the rate of a chemical reaction.
• The rate of reaction is accelerated by a positive catalyst.
• The rate of reaction is slowed by a negative catalyst.
• Catalyst has no effect on the number of products produced.
• Enzymes are bio-catalyst, which are temperature and pH sensitive, they lose their function when the pH or temperature increases or decreases.

Explanation:

• A catalyst is a substance which alters the rate of a reaction without itself undergoing any permanent chemical change.
• According to intermediate complex theory, reactants first combine with catalyst to form intermediate complex which then decomposes to form the products and regenerating the catalyst.

• Catalyst provides an alternate pathway by reducing the activation energy between reactants and products and hence lowering the potential energy barrier.
• Enzymes are the biological catalyst which are temperature and pH sensitive, they lose their function when the pH or temperature increases or decreases.

Thus, the statement, catalysts do not get the involved process of reaction is incorrect.

Concept:

• A catalyst is any material in chemistry that increases the rate of a reaction without being ingested.
• A small amount of the catalyst can catalyse a large amount of reactants.
• A catalyst does not alter Gibbs energy of a reaction.
• It catalyses the spontaneous reactions but does not catalyse non-spontaneous reactions.
• A catalyst does not change the equilibrium constant of a reaction rather, it helps in attaining the equilibrium faster.
• A catalyst is a material that speeds up or slows down the rate of a chemical reaction.
• The rate of reaction is accelerated by a positive catalyst.
• The rate of reaction is slowed by a negative catalyst.
• Catalyst has no effect on the number of products produced.
• Enzymes are bio-catalyst, which are temperature and pH sensitive, they lose their function when the pH or temperature increases or decreases.

Explanation:

• A catalyst is a substance that speeds up of a chemical reaction, or lowers the temperature or pressure needed to start the reaction, without itself being consumed during the reaction.
• Catalysis is the process of adding a catalyst to facilitate a reaction.
• The presence of a catalyst increases the reaction rate (in both forward and reverse reactions) by providing an alternative pathway with lower activation energy.
• If the activation energy is lowered, more reactants can cross that barrier easily so, the rate of effective collision also increased and so, the rate of reaction increases.
• Photocatalyst absorb the energy of different wavelength and provide them to reactants in the desired wavelength.
• A catalyst can lower the activation energy for a reaction by: orienting the reacting particles in such a way that successful collisions are more likely.
• Catalyst reacting with the reactants to form an intermediate that requires lower energy to form the product.

Thus, all the given options are correct.

Concept:

• A catalyst is any material in chemistry that increases the rate of a reaction without being ingested.
• A small amount of the catalyst can catalyse a large amount of reactants.
• A catalyst does not alter Gibbs energy of a reaction.
• It catalyses the spontaneous reactions but does not catalyse non-spontaneous reactions.
• A catalyst does not change the equilibrium constant of a reaction rather, it helps in attaining the equilibrium faster.
• A catalyst is a material that speeds up or slows down the rate of a chemical reaction.
• The rate of reaction is accelerated by a positive catalyst.
• The rate of reaction is slowed by a negative catalyst.
• Catalyst has no effect on the number of products produced.
• Enzymes are bio-catalyst, which are temperature and pH sensitive, they lose their function when the pH or temperature increases or decreases.

Explanation:

• Conversion of vanaspati oil to vanaspati ghee is known as Hydrogenation.
• Vegetable oils are unsaturated compounds.
• On heating of vegetable oils in the presence of nickel catalyst converts the unsaturated fat to saturated fats called vegetable ghee also known as vanaspati ghee.
• This process is known the hydrogenation of vegetable oils.

• In this process, oils are adsorbed on the surface of the catalyst along with some of the hydrogen.
• Hydrogens shift from the metal surface to the carbons of the double bonds present in the oils and the resulting saturated hydrocarbon which is more weakly adsorbed, leaves the catalyst surface.
• The nickel catalyst is then removed from the hydrogenated fat by the process of filtration.

Thus, raney nickel is used in the hydrogenation of Vanaspati oil.

Concept:

• A catalyst is any material in chemistry that increases the rate of a reaction without being ingested.
• A small amount of the catalyst can catalyse a large amount of reactants.
• It catalyses the spontaneous reactions but does not catalyse non-spontaneous reactions.
• A catalyst does not change the equilibrium constant of a reaction rather, it helps in attaining the equilibrium faster.
• A catalyst is a material that speeds up or slows down the rate of a chemical reaction.
• The rate of reaction is accelerated by a positive catalyst.
• The rate of reaction is slowed by a negative catalyst.
• When the reactants and the catalyst are in the same phase (i.e. solid, liquid or gas). The catalysis is said to be homogeneous
• Enzymes are bio-catalyst, which are temperature and pH sensitive, they lose their function when the pH or temperature increases or decreases.

Explanation:

• Catalyst is a substance which speeds up and speeds down a chemical reaction without itself being used up at the end of the reaction and the phenomenon is known as catalysis.
• The catalytic process in which the reactants and the catalyst are in different phases is known as heterogeneous catalysis.
• Catalytic poisons : Substances which destroy the activity of the catalyst by their presence are known as catalytic poisons.
• The catalyst provides a new pathway involving lower amount of activation energy.
• Selectivity is the ability of catalysts to direct a reaction to yield particular products (excluding other).
• A particular catalyst catalyses only one kind of reaction.

Thus, only option 3 is correct regarding catalyst.