Chemistry · Physics

Thermodynamics and Chemical Kinetics

1,132 Questions

Thermodynamics and chemical kinetics are crucial branches of physical chemistry. This area focuses on energy transformations, reaction rates, equilibrium constants, and catalysts. These topics carry significant weight in competitive science and engineering examinations.

Enthalpy and energyChemical equilibriumEntropy conceptsReaction kinetics and catalysts

Thermodynamics and Chemical Kinetics Questions

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

In case of autocatalysis: 

  1. reactant catalyses

  2. heat produced in the reaction catalyses

  3. product catalyses

  4. solvent catalyses
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Autocatalysis is the reaction where one of the products formed catalyzes the reaction. So in case of auto catalysis product catalyses the reaction. Hence catalysis of a reaction by one of its products is called autocatalysis.

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

Which of the following are correct about the catalyst?

  1. They participate in the reaction but recovered at last
  2. It does not affect $\Delta G $
  3. It increases $\Delta G $

  4. It alters the mechanism of reaction
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation

The catalyst is the substance which increases the rate of reaction by lowering the activation energy which alters the mechanism of the reaction.

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

Which statement of the following is false for a catalyst?

  1. A catalyst can initiate a reaction.

  2. It does not alter the position of equilibrium in a reversible reaction.

  3. A catalyst remains unchanged in quality and composition at the end of the reaction.

  4. Catalysts are sometimes very specific in reaction.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Catalysis is the increase in the rate of a chemical reaction due to the participation of an additional substance called a catalyst which is not consumed in the catalysed reaction and can continue to act repeatedly.It increase rate of forward as well as backward reaction.

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

An inhibitor is described as:

  1. a substance that slows down or stops a reaction

  2. a substance which inhibits the properties of a catalyst

  3. a substance formed during the reaction and does not participate in the reaction

  4. a substance which prevents formation of products in a reaction being most reactive
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A reaction inhibitor is a substance that decreases the rate of, or prevents, a chemical reaction. A catalyst, in contrast, is a substance that increases the rate of a chemical reaction.

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

Which of the following statements is/are correct ?

  1. The efficiency of a heterogeneous catalyst depends upon its surface area.

  2. Catalyst operates by providing alternate path for the reaction that involves a lower activation energy.

  3. Catalyst lowers the energy of activation of the forward direction without affecting the energy of activation of the backward direction

  4. Catalyst does not affect the overall enthalpy change of the reaction.
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation
  • A catalyst that is in a separate phase from the reactants is said to be a heterogeneous, or contact, catalyst. An example of heterogeneous catalysis is the use of finely divided platinum to catalyze the reaction of carbon monoxide with oxygen to form carbon dioxide. The efficiency of a heterogeneous catalyst depends on the surface area, more the surface area more easier the catalysis occurs.
  • Collisions only result in a reaction if the particles collide with certain minimum energy called the activation energy for the reaction. A catalyst provides an alternative route for the reaction with lower activation energy. It does not "lower the activation energy of the reaction".
  • Lowering the Activation Energy of a Reaction by a Catalyst. The only effect of the catalyst is to lower the activation energy of the reaction. The catalyst does not affect the energy of the reactants or products. Thus it doesn't affect $\Delta H$.
Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

A catalyst in finely divided state is more efficient because in this state_______.

  1. It has got large activation energy

  2. It can react with one reactant more effectively

  3. It has large surface area

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A catalyst in finely divided state is more efficient because in this state it has large surface area.
Higher is the surface area, higher is the catalytic efficiency and vice versa.

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

Decrease in activation energy is due to :

  1. an increase in the reactant concentration

  2. an increase in the temperature

  3. a decrease in pressure

  4. catalysts
  5. $\displaystyle pH$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Catalysis is the increase in the rate of a chemical reaction due to the participation of an additional substance called a catalyst. With a catalyst, reactions occur faster and require less activation energy. Because catalysts are not consumed in the catalyzed reaction, they can continue to catalyze the reaction of further quantities of reactant. Often only tiny amounts are required

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

$ Y\xleftarrow[]{\Delta,205^{\circ}C} CaSO 4.2H _2O\  \xrightarrow[]{\Delta,120^{\circ}C} X $. 


$X$ and $Y$ are respectively _____.

  1. plaster of paris, dead burnt plaster

  2. dead burnt plaster, plaster of paris
  3. $CaO$, plaster of paris

  4. plaster of paris, mixture of gases
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Reaction of process:


  $CaSO _4 \xleftarrow[]{\Delta,205^{\circ}C} CaSO _4.2H _2O \xrightarrow[]{\Delta,120^{\circ}C} CaSO _4.(1/2)H _2O$                                                                                           (dead burnt plaster)                                          (plaster of paris)
Anhydrous Calcium sulphate is known as dead burnt plaster and $CaSO _4.\cfrac{1}{2} H _2O$ is called plaster of paris.
Hence, the correct option is $A$.

Multiple choice physics energy management solar power plant production of electricity from solar energy solar equipment solar energy and its applications

In a steady state process, which of the following quantity remains constant throughout the process

  1. Enthalpy

  2. Entropy

  3. Temperature and heat both

  4. Internal energy
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A steady state is a state which remains the same over given time period. In heat transfer problems if there is specific rate of heat transfer through medium (for conduction or convection) and if it remains constant at any time then it is said to have steady state heat transfer. In steady state, there may be different temperatures in body at different locations but the temperature at any given point will remain constant. If the temperature at all locations is same then it is uniform.

n a steady state process, Internal energy is quantity remains constant throughout the process

Multiple choice chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

Selection of temperature to carry out a reduction process depends so as to make:

  1. $\Delta G$ negative
  2. $\Delta G$ positive
  3. $\Delta H$ negative
  4. $\Delta H$ positive
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When $\Delta$G is negative, a process or chemical reaction proceeds spontaneously in the forward direction and similar condition is required for a reduction process also. 

Multiple choice zoology meaning of life energy flow and loss energy flow in a food chain energy flows

One way cycle is

  1. CO$ _2$ cycle
  2. H$ _2$O cycle

  3. Free energy cycle
  4. O$ _2$ cycle
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Free energy cycle is the unidirectional cycle in our ecosystem. In other cycles like oxygen cycle, carbon dioxide cycle and water cycle, the basic elements are circulated and cycled whereas, in free energy cycle, energy flows from solar energy to producers and then consumers to decomposers. 


Multiple choice zoology meaning of life energy flow and loss energy flow in a food chain energy flows

Maintenance of internal favourable conditions, despite changes in external environment is

  1. Entropy

  2. Steady state

  3. Enthalpy

  4. Homeostasis
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Higher animals like mammals tend to maintain a constant internal environment despite changes in external environment. This is called as homeostasis, e.g., in humans a body temperature around 97 fahrenheit is considered normal. In summers when outside temperature is high or in winters when outside temperature is very low the body temperature remains constant. This is one example of homeostasis. The nervous and endocrine system closely interplay to maintain homeostasis. Therefore, the correct answer is option D.

Multiple choice zoology meaning of life energy flow and loss energy flow in a food chain energy flows

The movement of energy and nutrients through living systems differs in what way? 

  1. Energy recycles while nutrients flow in two directions.

  2. Nutrients recycle while energy flows in one direction.

  3. Nutrients are lost as heat while energy forms chemical compounds.

  4. Nutrients are constantly available while energy is limited.

  5. Nutrients are lost as heat while energy is limited.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Energy is passed from one trophic level to the next trophic level. Hence energy flows in one direction through successive trophic levels in a food chain. Nutrients are produced from the matter. The matter may be organic or inorganic. The organic and inorganic matter is produced, exchanged and moved within the ecosystem and this is called cycling. Hence nutrients are recycled.
So, the correct answer is 'Nutrients recycle while energy flows in one direction'.
Multiple choice zoology meaning of life energy flow and loss energy flow in a food chain energy flows

Which best describes the movement of energy and matter through living systems? 

  1. Energy flows while matter is cycled.

  2. Matter flows in two directions while energy flows in one direction.

  3. Energy is cycled while some matter is lost as heat.

  4. Energy forms chemical compounds while matter flows.

  5. Matter is always available while energy is cycled.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Energy is passed from one trophic level to the next trophic level. Hence energy flows through successive trophic levels in a food chain. 
Matter may be organic or inorganic. The organic and inorganic matter is produced, exchanged and moved within the ecosystem and this is called cycling. Hence matter is cycled.
So, the correct answer is 'Energy flows while matter is cycled'.