Aga Khan University Examination Board Chemistry (SSC IX-X) Syllabus

How many moles are in 36 g of water?

36 / 18 = 2 moles.

What is an empirical formula?

The simplest whole-number ratio of atoms of each element present in a compound, e.g., CH2O for glucose.

What is a molecular formula?

The formula showing the actual number of atoms of each element present in one molecule of a compound, e.g., C6H12O6 for glucose.

How is the molecular formula related to the empirical formula?

Molecular formula = n x (empirical formula), where n = molecular mass / empirical formula mass.

What is the empirical formula of benzene (C6H6)?

CH (the simplest ratio of C to H is 1:1).

State the steps to find an empirical formula from percentage composition.

Divide each element's percentage by its atomic mass to get moles, then divide all values by the smallest to get the simplest whole-number ratio.

State Boyle's Law.

At constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure; PV = constant, or P1V1 = P2V2.

State Charles's Law.

At constant pressure, the volume of a fixed mass of gas is directly proportional to its absolute (Kelvin) temperature; V/T = constant, or V1/T1 = V2/T2.

How do you convert Celsius temperature to Kelvin?

K = degrees C + 273.

What is the value of standard temperature and pressure (STP)?

Standard temperature = 0 degrees C (273 K) and standard pressure = 1 atm (760 mmHg / 101.325 kPa).

What is absolute zero?

The lowest possible temperature, 0 K (-273 degrees C), at which the volume of an ideal gas theoretically becomes zero and molecular motion stops.

List the main postulates of the kinetic molecular theory of gases.

Gas molecules are tiny and far apart, in constant random motion, have negligible volume and forces, and collisions are perfectly elastic; their kinetic energy is proportional to absolute temperature.

Define diffusion.

The spontaneous spreading and mixing of particles of one substance through another due to their random motion (e.g., gases mixing).

What is evaporation?

The process by which molecules at the surface of a liquid escape into the gaseous state below the boiling point.

What is vapour pressure of a liquid?

The pressure exerted by the vapour in equilibrium with its liquid at a given temperature in a closed container.

How does vapour pressure relate to boiling point?

A liquid boils when its vapour pressure equals the external (atmospheric) pressure; lower external pressure means a lower boiling point.

Define boiling point.

The temperature at which the vapour pressure of a liquid becomes equal to the external atmospheric pressure and the liquid changes to vapour throughout.

What is surface tension?

The force acting along the surface of a liquid that tends to minimize its surface area, caused by inward attraction of surface molecules.

How does temperature affect the viscosity of a liquid?

Increasing temperature decreases the viscosity of a liquid because molecules gain energy and flow more easily.

What are the characteristic properties of solids?

Fixed shape and volume, particles closely packed in fixed positions, incompressible, with strong intermolecular forces and only vibrational motion.

What is allotropy?

The existence of an element in two or more different physical forms in the same physical state, e.g., carbon as diamond and graphite.

Compare diamond and graphite as allotropes of carbon.

Diamond is hard, non-conducting, with each carbon bonded to 4 others in a 3D network; graphite is soft, slippery, conducts electricity, with carbon in layers bonded to 3 others.

What is sublimation?

The direct change of a substance from the solid state to the gaseous state without passing through the liquid state (e.g., iodine, naphthalene).

Name the change of state from liquid to solid and from solid to liquid.

Liquid to solid is freezing (solidification); solid to liquid is melting (fusion).

What is the freezing point of a substance?

The temperature at which a liquid changes into a solid; it is the same as its melting point.

What did Rutherford's atomic model propose?

The atom has a small, dense, positively charged nucleus at the center, with electrons revolving around it; most of the atom is empty space.

What did Bohr's atomic model propose?

Electrons revolve around the nucleus in fixed circular orbits (energy levels/shells) without radiating energy, and absorb or emit energy only when jumping between orbits.

What were the main features of Dalton's atomic theory?

Matter is made of indivisible atoms; atoms of an element are identical; atoms combine in simple whole-number ratios; and atoms are neither created nor destroyed in reactions.

What are the three sub-atomic particles, their charges, and locations?

Proton (+1, in nucleus), neutron (0, in nucleus), and electron (-1, orbiting the nucleus); proton and neutron each have ~1 amu mass, electron mass is negligible.

What is the maximum number of electrons in the first three shells (2n^2 rule)?

K shell (n=1) = 2, L shell (n=2) = 8, M shell (n=3) = 18 electrons.

Write the electronic configuration of a chlorine atom (atomic number 17).

2, 8, 7 (K=2, L=8, M=7).

Define isotopes.

Atoms of the same element having the same atomic number (protons) but different mass numbers (different numbers of neutrons).

Give the three isotopes of hydrogen and their mass numbers.

Protium (mass 1, 0 neutrons), Deuterium (mass 2, 1 neutron), and Tritium (mass 3, 2 neutrons).

State two important applications of isotopes.

Carbon-14 is used in radiocarbon dating; cobalt-60 and iodine-131 are used in medicine to treat cancer and diagnose thyroid disorders.

What is the difference between atomic number and mass number?

Atomic number = number of protons in the nucleus; mass number = total number of protons plus neutrons.