ATOMIC THEORY

Question 1

Who discovered that atoms were the smallest indivisible particles of an element

Answer 1

John Dalton (18th century)

Question 2

What was the limitation of dalton’s atomic theory

Answer 2

He did not explain the existence of isotopes

Question 3

What were the postulates in dalton’s atomic theory

Answer 3

• Atoms are the smallest indivisible particle of an element
• Atoms of the same elements are alike in every aspect but differ from that of other elements
• Every chemical reaction is as a result of the combination or separation of atoms
• Atoms combine in small amounts/quantities to produce molecules

Question 4

State the law of definite proportion and give another name for it

Answer 4

All pure samples of a compound contains similar elements in the same proportion by mass (Law of constant composition)

Question 5

State the law of multiple proportion

Answer 5

When two elements A and B combine to form more than one compound, then the various masses of element A that combines with a fixed mass of element B are in simple ratio to one another

Question 6

What are isotopes

Answer 6

Isotopes are atoms of the same element that have the same number of protons and electrons but different number of neutrons

Question 7

Why does dalton’s atomic THEORY still hold inspite of isotopes

Answer 7

The discovery of isotopes would mean that atoms of the same element would have different masses, but since isotopes are present in fixed proportions, the average mass of atoms is still constant and the theory still holds

Question 8

What happens when the neutron number of an isotope is too high

Answer 8

The nucleus becomes unstable and the element becomes radioactive

Question 9

Who created the mass spectrometer

Answer 9

Aston (1919)

Question 10

What is used to measure the atomic masses of elements

Answer 10

Mass spectometer

Question 11

What are the five stages involved in measuring atomic mass using a mass spectrometer

Answer 11

• The atoms is vaporized
• +ve ions are discharged
• +ve ions are accelerated by electric field
• the ions are deflected by a magnetic field
• ## the ions are detected on reaching the detector and record is made

Question 12

How are the +ve ions in the mass spectrometer created

Answer 12

They are created by bombarding neutral atom with high energy electrons

Question 13

What is mole

Answer 13

Mole is the amount of a substance that contains as many particles(6.02 × 10²³) as are in 12g of carbon-12

Question 14

How are the elements in the periodic table arranged

Answer 14

Thay are arranged in order of increasing atomic number

Question 15

What is excitation

Answer 15

This is when an electron moves from lower energy level to a higher energy level

Question 16

What happens when an electron is exited

Answer 16

It becomes unstable and gives out the excess energy in form of radiation which produces a spectrum

Question 17

What is ionization energy

Answer 17

Ionization energy is the amount of energy required to remove an electron from a gaseous atom in its ground state

Question 18

Why is the ionization energy of noble gases high

Answer 18

They are stable

Question 19

What branch of chemistry deals with the weight relations between elements and compound in a chemical equation

Answer 19

Stoichometry

Question 20

What are the shapes of the s and p orbital

Answer 20

S orbital - spherical
P orbital - dumbbell

Question 21

Where is the nucleus located in the p orbital

Answer 21

Below the two halves of the dumb bell

Question 22

State Boyle’s law

Answer 22

Boyle’s law(1662) states that the volume of a fixed mass of gas is inversely proportional to its pressure at constant temperature

Question 23

At what pressure is Boyle’s law properly obeyed

Answer 23

At or below 1 atm

Question 24

What are the types of cohesive forces

Answer 24

Electovalent /ionic
Covalent
Metallic
Vanderwaal

Question 25

Mention some phenomena that support kinetic theory

Answer 25

Brownian motion
Osmosis
Diffusion

Question 26

What are the assumptions of kinetic theory

Answer 26

• Gas particles are in constant rand motion in a straight line
• Their collisions are perfectly elastic
• Their collisions with the walls of the container results in pressure
• The volume fo gases are negligible when compared to the volume occupied
• The cohesive forces between gas particles are negligible
• Tbe temperature is a measure of the average kinetic energy of the particles

Question 27

State Charles’s law

Answer 27

At constant pressure, the volume of a given mass of gas is directly proportional to the temperature

Question 28

State dalton’s law of partial pressure

Answer 28

(1802)It states that when there is a mixture of gases which do not react chemically together, the total pressure of the system is the sum of the partial pressures of the individual elements

Question 29

State Graham’s law of diffusion

Answer 29

(1833) It states that the rate of diffusion of a gas is inversely proportional to the square root of its density

Question 30

What is the critical temperature of a gas

Answer 30

It is the temperature above which a gas cannot be liquefied by pressure

Question 31

What is the critical pressure of a gas

Answer 31

It is the pressure at which the critical temperature is just enough to liquify the gas

Question 32

Mention some applications of Graham’s law

Answer 32

• it’s used to separate mixed gases(atmolysis)
• It’s used to determine density of gases

Question 33

State gay-lussac’s law of combining volumes

Answer 33

It states that when gases react, they do so in volumes which are simple ratios to one another and to the volumes of their products if gaseous provided that the temperature and pressure are kept constant

Question 34

State avogadro’s hypothesis

Answer 34

It sates that equal volume of all the gases at the same temperature and pressure contain the same number of molecules

Question 35

When do avogadro and Gay-lusaac laws hold

Answer 35

At low pressures

Question 36

Root mean square velocity

Answer 36

(3RT/m(in kg/mol))½