Part One: Multiple Choice

Here are the solutions to the questions: Part One: Multiple Choice 1. To determine the electron arrangement of a Group One element, we look for an atom with one valence electron. a) 2, 8, 1: This arrangement has 1 electron in the outermost shell. b) 2, 2: This has 2 valence electrons. c) 2, 8, 8: This has 8 valence electrons. d) 2, 4: This has 4 valence electrons. Group One elements have 1 valence electron. The correct option is a) 2, 8, 1. 2. Step 1: Calculate the molar mass of CO_2. Molar mass of CO_2 = RAM of C + (2 × RAM of O) Molar mass of CO_2 = 12 + (2 × 16) = 12 + 32 = 44 g/mol Step 2: Calculate the mass of 2 moles of CO_2. Mass = Moles × Molar mass Mass = 2 mol × 44 g/mol = 88 g The correct option is c) 88 grams. 3. Small units that join together to form a polymer are called monomers. The correct option is a) Monomers. 4. The chemical symbol for Magnesium is Mg. The correct option is a) Mg. 5. At Room Temperature and Pressure (RTP), 1 mole of any gas occupies a volume of 24 L. The correct option is b) 24 L. 6. Step 1: Determine the number of electrons in a neutral calcium atom. Calcium (Ca) has an atomic number of 20, meaning a neutral calcium atom has 20 protons and 20 electrons. Step 2: Determine the number of electrons in the calcium ion Ca^2+. The Ca^2+ ion has lost 2 electrons. Number of electrons = 20 - 2 = 18 electrons The correct option is b) 18 electrons. 7. Atomic radius generally decreases across a period and increases down a group. Na (Period 3, Group 1) Cl (Period 3, Group 17) K (Period 4, Group 1) Ar (Period 3, Group 18) Comparing elements in Period 3 (Na, Cl, Ar), atomic radius decreases from left to right. So, Ar has a smaller radius than Na and Cl. K is in Period 4, so it is larger than all Period 3 elements. Therefore, Ar has the smallest atomic radius among the given options. The correct option is d) Ar. 8. Step 1: Calculate the molar mass of calcium oxide (CaO). Molar mass of CaO = RAM of Ca + RAM of O Molar mass of CaO = 40 + 16 = 56 g/mol Step 2: Calculate the mass percent of calcium in CaO. Mass percent of Ca = ( Mass of CaMolar mass of CaO ) × 100\% Mass percent of Ca = ( 40 g/mol56 g/mol ) × 100\% Mass percent of Ca ≈ 0.71428 × 100\% ≈ 71.4\% The closest option is a) 72.4%. 9. An s-subshell contains only one orbital. The correct option is a) 1 orbitals. 10. The process where large molecules are broken down into smaller, more useful molecules is called cracking. The correct option is c) Cracking. 11. Alcohols can undergo various reactions to form different compounds: Dehydration can form ethers. Oxidation can form aldehydes (primary alcohols) and then carboxylic acids. Therefore, alcohols can be converted to ethers, aldehydes, and carboxylic acids. The correct option is d) All of the above. 12. An ionic bond is formed when electrons are transferred from one atom to another, typically between a metal and a non-metal. The correct option is b) Ionic bond. 13. Oil and water are immiscible liquids and can be separated using a separating funnel. The correct option is c) Separating funnel. 14. The reaction CaCO_3 CaO + CO_2 shows one compound breaking down into two simpler compounds. This is a decomposition reaction. The correct option is b) Decomposition. 15. In electrolysis, the negative electrode is called the cathode. Cations (positive ions) are attracted to the cathode and undergo reduction. The correct option is b) Cathode. 16. At the anode (positive electrode) during electrolysis, negative ions (anions) are attracted and lose electrons (oxidation). The correct option is b) Negative ions lose electrons. 17. The reactivity of metals with acids depends on their position in the reactivity series. Metals above hydrogen in the series react with acids. Zinc (Zn) is above hydrogen and reacts vigorously with HCl, while copper (Cu), silver (Ag), and gold (Au) are below hydrogen and do not react with dilute HCl. The correct option is b) Zn. 18. Sulfur is the non-metal used in the vulcanization process to improve the elasticity and durability of rubber. The correct option is b) Sulfur. 19. Bismuth is a chemical element with the symbol Bi. The correct option is d) Bi. 20. Ammonium nitrate (NH_4NO_3) is a common artificial fertilizer, providing nitrogen to plants. The correct option is c) Ammonium nitrate. PART TWO: Structured Questions 1. a) Calculate the molar mass of HCl (H = 1, Cl = 35.5). Step 1: Sum the atomic masses of the constituent atoms. Molar mass of HCl = (RAM of H × 1) + (RAM of Cl × 1) Molar mass of HCl = (1 × 1) + (35.5 × 1) = 1 + 35.5 = 36.5 g/mol b) How many moles are there in 7 g of HCl? Step 1: Use the formula for moles. Moles = MassMolar mass Moles of HCl = 7 g36.5 g/mol ≈ 0.192 mol c) How many grams are there in 5 moles of HCl? Step 1: Use the formula for mass. Mass = Moles × Molar mass Mass of HCl = 5 mol × 36.5 g/mol = 182.5 g 2. a) State the number of protons and electrons of the three atoms: For a neutral atom, the number of protons is equal to the atomic number, and the number of electrons is equal to the number of protons. Atom A: Atomic Number = 12. Protons = 12, Electrons = 12. Atom B: Atomic Number = 6. Protons = 6, Electrons = 6. Atom C: Atomic Number = 26. Protons = 26, Electrons = 26. b) State the number of neutrons of the three atoms: The number of neutrons is calculated as Mass Number - Atomic Number. Atom A: Neutrons = 24 - 12 = 12 neutrons. Atom B: Neutrons = 12 - 6 = 6 neutrons. Atom C: Neutrons = 56 - 26 = 30 neutrons. c) What name is given to atoms of the same element but different mass numbers? The name given to atoms of the same element (same number of protons) but different mass numbers (different number of neutrons) is Isotopes. 3. a) Which one is the most reactive element in Group 7? Reactivity in Group 7 (halogens) decreases down the group. Therefore, the element at the top of the group is the most reactive. The most reactive element in Group 7 is Fluorine. b) Which one has a higher boiling point, chlorine or iodine? From the table: Chlorine boiling point: -34^ Iodine boiling point: 184^ Iodine has a higher boiling point than chlorine. c) What happens to the size of the atoms as we go down the group? As you move down Group 7, the size of the atoms increases. This is because additional electron shells are added, and the increased shielding reduces the effective nuclear charge on the outermost electrons, causing them to be held less tightly and further from the nucleus. 4. a) How many electrons are in sodium (Na)? Sodium (Na) has an atomic number of 11. In a neutral atom, the number of electrons is equal to the atomic number. Sodium has 11 electrons. b) Name the type of bond formed when these atoms react. Sodium (a metal) reacts with chlorine (a non-metal) by transferring an electron from sodium to chlorine. This forms an ionic bond. c) Why do ionic compounds have a higher melting and boiling points than simple molecular compounds? Ionic compounds have strong electrostatic forces of attraction between the positively and negatively charged ions in their crystal lattice. A large amount of energy is required to overcome these strong forces, resulting in high melting and boiling points. Simple molecular compounds, on the other hand, have weak intermolecular forces that require much less energy to overcome. 5. a) Name the small molecules that are joined together to form a polymer. The small molecules that join together to form a polymer are called monomers. b) What do we mean by the term copolymer? A copolymer is a polymer formed from two or more different types of monomers. c) Give one example of a natural polymer and one example of a synthetic polymer. Natural polymer: Cellulose (or starch, proteins, DNA). Synthetic polymer: Polyethylene (or PVC, nylon, polyester). d) What are the two types of polymerization reactions? The two main types of polymerization reactions are addition polymerization and condensation polymerization. 6. a) Work out the molar mass of Calcium Carbonate (CaCO_3). Given RAM: Ca = 40, C = 12, O = 16. Molar mass of CaCO_3 = RAM of Ca + RAM of C + (3 × RAM of O) Molar mass of CaCO_3 = 40 + 12 + (3 × 16) = 40 + 12 + 48 = 100 g/mol b) Calculate the mass percent of calcium in CaCO_3. Mass percent of Ca = ( Mass of CaMolar mass of CaCO_3 ) × 100\% Mass percent of Ca = ( 40 g/mol100 g/mol ) × 100\% = 40% c) Calculate the mass percent of Oxygen in CaCO_3. Mass percent of O = ( Mass of O in CaCO_3Molar mass of CaCO_3 ) × 100\% Mass percent of O = ( 3 × 16 g/mol100 g/mol ) × 100\% = ( 48 g/mol100 g/mol ) × 100\% = 48% 7. a) List the ions present in the solution (molten Lead (II) bromide). Molten Lead (II) bromide (PbBr_2) dissociates into: Lead (II) ions (Pb^2+) Bromide ions (Br^-) b) Write down the half-equation of reactions at each electrode: At the anode (oxidation): Negative bromide ions lose electrons. 2Br^- Br_2 + 2e^- At the cathode (reduction): Positive lead ions gain electrons. Pb^2+ + 2e^- Pb c) State any two uses of electrolysis. 1. Electroplating: Used to coat metals with a thin layer of another metal for decorative purposes or to prevent corrosion. 2. Extraction of metals: Used to extract reactive metals (e.g., aluminum, sodium) from their ores. 3. Purification of metals: Used to purify metals like copper. 8. a) Name the two materials used to prepare Oxygen in the laboratory. Based on the diagram showing hydrogen peroxide and a solid catalyst: 1. Hydrogen peroxide (H_2O_2) 2. Manganese dioxide (MnO_2) (as the catalyst) b) State the catalyst used in the above process. The catalyst used is Manganese dioxide (MnO_2). c) Write down a balanced chemical equation for the reaction in the above process. 2H_2O_2 MnO_2 2H_2O + O_2 9. a) Name the method used to separate salt from a salt solution. The method shown, involving heating to remove water and leave a solid, is evaporation. b) Which substance remains in the evaporation dish? The substance that remains in the evaporation dish is the salt. c) What happens to the water during these processes? The water evaporates (changes from liquid to gas) and leaves the system. 10. a) What is electroplating? Electroplating is a process that uses electric current to deposit a thin layer of metal onto a conductive surface. This is typically done to enhance appearance, prevent corrosion, or improve wear resistance. b) What happens to the anode during the electroplating process? In electroplating, if the anode is made of the metal to be deposited (e.g., copper anode for copper plating), the anode dissolves, releasing metal ions into the electrolyte solution. These ions then migrate to the cathode to be deposited. c) List any two uses of electroplating. 1. Decorative purposes: To coat objects with precious metals like gold or silver to improve their appearance. 2. Corrosion protection: To apply a protective layer of a less reactive metal (e.g., chromium, nickel) onto a more reactive metal to prevent rust and corrosion. 3. Enhancing properties: To improve hardness, wear resistance, or electrical conductivity of a surface. Send me the next one 📸