(a) Distinguish between molecular formula and structural formula
(b) List three factors that determine the ionization energy of an atom.
(c) State the two conditions necessary for the establishment of a chemical equilibrium
(d) Consider the following table
| Element |
A |
B |
C |
| Ionization energy KJ mol\(^{-1}\) |
619 |
518 |
594 |
(d)(i) State which of the elements is the strongest reducing agent.
(ii) Give a reason for the answer stated in (d)(i)
(e) State Graham's law of diffusion
(f) Consider the following salts: Mg(NO\(_{3}\))\(_{2}\), CaCO\(_{3}\), Na\(_{2}\)SO\(_{4}\). State which of the salts is/are:
(i) readily soluble in water:
(ii) insoluble in water.
(g) Classily each of the following products as addition polymer or condensation polymer:
(i) protein:
(ii) perspex:
(iii) nylon.
(h) Define atomic radius.
(i) Explain briefly why ethanol has a higher boiling point than propane even though they both have comparable molar masses.
(j) State three significance of the pH value in everyday life.
(a) Molecular formula and structural formula are both used to represent the composition of a molecule, but they differ in their level of detail. A molecular formula simply shows the types and numbers of atoms in a molecule, while a structural formula shows the arrangement of atoms and the bonds between them.
(b) The three factors that determine the ionization energy of an atom are:
- Nuclear charge: the more protons an atom has, the stronger the pull on the electrons, which makes it harder to remove an electron.
- Distance from the nucleus: the further away an electron is from the nucleus, the weaker the attraction to the nucleus, which makes it easier to remove an electron.
- Shielding effect: the more inner shells of electrons an atom has, the less the outer electrons feel the pull of the nucleus, which makes it easier to remove an electron.
(c) The two conditions necessary for the establishment of a chemical equilibrium are:
- A reversible reaction: a reaction that can proceed in both forward and reverse directions.
- A closed system: a system in which no reactants or products can escape or be added from the outside.
(d)(i) Element B is the strongest reducing agent because it has the lowest ionization energy, which means it is easier for it to lose electrons and be oxidized.
(ii) A reducing agent is a substance that donates electrons to another substance and gets oxidized in the process. Element B has the lowest ionization energy, so it is easier for it to lose electrons and become oxidized, making it a stronger reducing agent.
(e) Graham's law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of its molar mass. In other words, lighter gases diffuse faster than heavier gases.
(f)
(i) Na2SO4 is readily soluble in water.
(ii) CaCO3 and Mg(NO3)2 are insoluble in water.
(g)
(i) Protein is a condensation polymer.
(ii) Perspex is an addition polymer.
(iii) Nylon is a condensation polymer.
(h) Atomic radius is the distance between the nucleus of an atom and its valence electrons.
(i) Ethanol has a higher boiling point than propane even though they have comparable molar masses because ethanol has stronger intermolecular forces due to its ability to form hydrogen bonds, while propane can only form weak London dispersion forces.
(j) Three significance of the pH value in everyday life are:
- Biological systems: the pH of bodily fluids such as blood and stomach acid must be maintained within a narrow range for proper functioning of enzymes and other biological processes.
- Household cleaning: certain cleaning products work best at specific pH values, such as acidic cleaners for removing mineral deposits and basic cleaners for removing grease and oils.
- Agriculture: the pH of soil can affect the availability of nutrients to plants and the growth of crops.
(a) Molecular formula and structural formula are both used to represent the composition of a molecule, but they differ in their level of detail. A molecular formula simply shows the types and numbers of atoms in a molecule, while a structural formula shows the arrangement of atoms and the bonds between them.
(b) The three factors that determine the ionization energy of an atom are:
- Nuclear charge: the more protons an atom has, the stronger the pull on the electrons, which makes it harder to remove an electron.
- Distance from the nucleus: the further away an electron is from the nucleus, the weaker the attraction to the nucleus, which makes it easier to remove an electron.
- Shielding effect: the more inner shells of electrons an atom has, the less the outer electrons feel the pull of the nucleus, which makes it easier to remove an electron.
(c) The two conditions necessary for the establishment of a chemical equilibrium are:
- A reversible reaction: a reaction that can proceed in both forward and reverse directions.
- A closed system: a system in which no reactants or products can escape or be added from the outside.
(d)(i) Element B is the strongest reducing agent because it has the lowest ionization energy, which means it is easier for it to lose electrons and be oxidized.
(ii) A reducing agent is a substance that donates electrons to another substance and gets oxidized in the process. Element B has the lowest ionization energy, so it is easier for it to lose electrons and become oxidized, making it a stronger reducing agent.
(e) Graham's law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of its molar mass. In other words, lighter gases diffuse faster than heavier gases.
(f)
(i) Na2SO4 is readily soluble in water.
(ii) CaCO3 and Mg(NO3)2 are insoluble in water.
(g)
(i) Protein is a condensation polymer.
(ii) Perspex is an addition polymer.
(iii) Nylon is a condensation polymer.
(h) Atomic radius is the distance between the nucleus of an atom and its valence electrons.
(i) Ethanol has a higher boiling point than propane even though they have comparable molar masses because ethanol has stronger intermolecular forces due to its ability to form hydrogen bonds, while propane can only form weak London dispersion forces.
(j) Three significance of the pH value in everyday life are:
- Biological systems: the pH of bodily fluids such as blood and stomach acid must be maintained within a narrow range for proper functioning of enzymes and other biological processes.
- Household cleaning: certain cleaning products work best at specific pH values, such as acidic cleaners for removing mineral deposits and basic cleaners for removing grease and oils.
- Agriculture: the pH of soil can affect the availability of nutrients to plants and the growth of crops.
