physical I (p1& 2)

Question 1

What is the definition of relative atomic mass (Ar)?

Answer 1

The relative atomic mass (Ar) of an element is the average mass of an atom of an element, compared to one-twelfth of the mass of an atom of carbon-12.

Question 2

What is the ideal gas equation?

Answer 2

PV=nRT

Question 3

What is the difference between an exothermic and an endothermic reaction?

Answer 3

• Exothermic reaction: Releases energy to the surroundings, usually as heat. (e.g., combustion, respiration)
• Endothermic reaction: Absorbs energy from the surroundings, usually as heat. (e.g., photosynthesis, thermal decomposition)

Question 4

How is the rate of reaction defined?

Answer 4

The rate of reaction is the change in the concentration of a reactant or product per unit time. It can be measured in terms of the speed at which reactants are used up or products are formed.

Question 5

What factors affect the rate of reaction?

Answer 5

• Temperature: Increasing temperature increases the rate.
• Concentration: Increasing the concentration of reactants increases the rate.
• Surface area: A larger surface area increases the rate.
• Catalysts: Catalysts increase the rate without being consumed in the reaction.

Question 6

What is meant by activation energy?

Answer 6

Activation energy is the minimum energy required for reactants to collide with enough energy to react and form products.

Question 7

What are the properties of ionic compounds?

Answer 7

• High melting and boiling points due to strong electrostatic forces.
• They conduct electricity when molten or in solution.
• They are usually soluble in water.

Question 8

What is an acid and a base according to the Arrhenius theory?

Answer 8

• Acid: A substance that increases the concentration of hydrogen ions (H⁺) in solution.
• Base: A substance that increases the concentration of hydroxide ions (OH⁻) in solution.

Question 9

What is pH?

Answer 9

pH is a measure of the acidity or alkalinity of a solution. It is calculated as the negative logarithm of the concentration of hydrogen ions:
pH=−log⁡[H+]

Question 10

What happens in a neutralization reaction?

Answer 10

HCl (aq)+NaOH (aq)→NaCl (aq)+H2O

Question 11

What is the process of distillation?

Answer 11

Distillation is a method of separating mixtures based on differences in boiling points. It involves heating the mixture to vaporize the component with the lower boiling point, then condensing the vapor back into liquid.

Question 12

What is the difference between oxidation and reduction in terms of electron transfer?

Answer 12

• Oxidation: The loss of electrons.
• Reduction: The gain of electrons.

Question 13

What is meant by dynamic equilibrium?

Answer 13

Dynamic equilibrium occurs in a reversible reaction when the rate of the forward reaction equals the rate of the reverse reaction, so the concentrations of reactants and products remain constant over time.

Question 14

What is Le Chatelier’s Principle?

Answer 14

Le Chatelier’s Principle states that if a system at equilibrium is disturbed by a change in temperature, pressure, or concentration, the system will shift to counteract the disturbance and restore equilibrium.

Question 15

What is a mole in chemistry?

Answer 15

A mole is the amount of substance that contains exactly 6.022×10^23 entities (atoms, molecules, or ions). This number is known as Avogadro’s number.

Question 16

What is the difference between a strong acid and a weak acid?

Answer 16

• Strong acid: Fully dissociates in water, releasing all its hydrogen ions (e.g., hydrochloric acid).
• Weak acid: Only partially dissociates in water, releasing some hydrogen ions (e.g., acetic acid).

Question 17

What is the purpose of titration in chemistry?

Answer 17

Titration is a technique used to determine the concentration of an unknown solution by reacting it with a solution of known concentration.

Question 18

What is the formula for calculating the energy change in a reaction?

Answer 18

ΔH=Energy of products−Energy of reactants

Question 19

What is the difference between a saturated and an unsaturated solution?

Answer 19

• Saturated solution: A solution in which no more solute can dissolve at a given temperature.
• Unsaturated solution: A solution in which more solute can dissolve at a given temperature.

Question 20

What is the rate of reaction?

Answer 20

The rate of reaction is the change in concentration of reactants or products per unit time. It is usually expressed in mol/dm³/s.

Question 21

What is a rate equation?

Answer 21

A rate equation shows the relationship between the rate of reaction and the concentration of reactants. It is in the form:

Rate=k[A] m[B] n

Where: k is the rate constant

[A] and [B] are the concentrations of reactants
m and n are the orders of reaction with respect to A and B.

Question 22

What does the order of reaction tell you?

Answer 22

The order of reaction indicates how the rate of reaction is affected by the concentration of a reactant. It can be:
o Zero order: rate is independent of concentration.
o First order: rate is directly proportional to concentration.
o Second order: rate is proportional to the square of concentration.

Question 23

What is the rate constant k?

Answer 23

The rate constant is a proportionality constant that links the rate of reaction to the concentrations of reactants. It is specific to a particular reaction at a given temperature.

Question 24

What factors affect the rate of reaction?

Answer 24

The rate of reaction can be influenced by:
1. Concentration of reactants
2. Temperature
3. Surface area of solid reactants
4. Presence of a catalyst

Question 25

What is collision theory?

Answer 25

Collision theory states that for a reaction to occur, particles must collide with sufficient energy (activation energy) and in the correct orientation.

Question 26

What is activation energy?

Answer 26

Activation energy is the minimum energy required for a successful collision to occur and for the reactants to be converted into products.

Question 27

What does the Maxwell-Boltzmann distribution show?

Answer 27

The Maxwell-Boltzmann distribution shows the distribution of energies among particles in a sample. As temperature increases, the peak of the distribution shifts to higher energies, and more particles have energy greater than or equal to the activation energy.

Question 28

How does temperature affect the rate of reaction?

Answer 28

Increasing temperature increases the rate of reaction because it:
o Increases the number of particles with energy greater than the activation energy.
o Increases the frequency of collisions.

Question 29

What is a catalyst?

Answer 29

A catalyst is a substance that increases the rate of a reaction by lowering the activation energy. It is not consumed in the reaction.

Question 30

What does a zero-order reaction mean?

Answer 30

In a zero-order reaction, the rate is independent of the concentration of the reactant. The rate law is: Rate=k.

Question 31

What does a first-order reaction mean?

Answer 31

In a second-order reaction, the rate is proportional to the square of the concentration of the reactant. The rate law is: {Rate} = k[A]^2Rate=k[A]2.

Question 32

What is the rate-determining step?

Answer 32

The rate-determining step is the slowest step in a reaction mechanism, which controls the overall rate of the reaction.

Question 33

What are some methods for measuring the rate of reaction?

Answer 33

Common methods include:
1. Measuring the volume of gas produced.
2. Monitoring the change in mass.
3. Measuring the change in color (using a colorimeter).
4. Monitoring the change in pH.

Question 34

What is oxidation?

Answer 34

Oxidation is the process in which an atom or ion loses electrons. It is often associated with an increase in oxidation state.

Question 35

What is reduction?

Answer 35

Reduction is the process in which an atom or ion gains electrons. It is often associated with a decrease in oxidation state.

Question 36

What is a redox reaction?

Answer 36

A redox (reduction-oxidation) reaction involves both oxidation and reduction processes occurring simultaneously. One species is oxidized (loses electrons), and another is reduced (gains electrons).