2016 JAMB CHEMISTRY PAST QUESTIONS AND ANSWERS

$$\text{Calculate relative atomic mass using weighted average: } \text{RAM} = \frac{(20 \times 1) + (22 \times 3)}{4}.\text{}$$

`textApplyGraham′slawofdiffusion:t1/t2=sqrtM2/M1.text\text{Apply Graham’s law of diffusion: } t_1/t_2 = \sqrt{M_2/M_1}.\text{}textApplyGraham′slawofdiffusion:t1​/t2​=sqrtM2​/M1​.text

$$\text{Valency refers to the combining capacity of an element, often reflected by its unpaired valence electrons.}$$

$$\text{Analyze protons, neutrons, and electrons from atomic number and mass. For example, helium has 2 protons and 2 neutrons.}$$

$$\text{Carbon monoxide binds to hemoglobin, reducing oxygen transport in blood, making it highly toxic.}$$

$$\text{Soft water dissolves lead from pipes, which may cause lead poisoning if consumed.}$$

$$\text{Aerobic bacteria break down hydrocarbons in oil spills, an eco-friendly method of remediation.}$$

$$\text{Carboxylic acids react with } \text{NaHCO}_3 \text{ to release } \text{CO}_2,\text{ forming bubbles.}$$

$$\text{Balance charge: } 2K (+2) + 2Cr + 7O (-14) = 0; \text{solve } \text{Cr} = +6.\text{}$$

$$\text{Oxidation involves loss of electrons. In } \text{Na}_2\text{O}_2, \text{O goes from -1 to 0 (oxidized).}$$

$$\text{Z denotes activation energy, which is the minimum energy required for reactants to form products.}$$

$$\text{The nucleus contains protons and neutrons, collectively called nucleons, as electrons orbit outside.}$$

$$\text{Zinc displaces copper due to its higher reactivity, leading to solution decolorization and heat release.}$$

$$\text{At the cathode, hydrogen gas is produced as water dissociates, increasing alkalinity.}$$

$$\text{Calcium carbide reacts with water to form ethyne, not any alkyne, making the statement incorrect.}$$

$$\text{Iron(III) oxide dissolves in NaOH, leaving alumina as a residue in the Bayer process.}$$

$$\text{Aluminum oxide is electrolyzed in molten cryolite to reduce its melting point, facilitating extraction.}$$

$$\text{Zinc carbonate decomposes to yellow ZnO when heated and forms soluble Zn(OH)}_2 \text{ in NaOH.}$$

$$\text{Copper has the lowest reactivity in the series, resisting oxidation more effectively.}$$

$$\text{Aluminum chloride forms covalent bonds due to its small, highly charged Al}^3+ \text{ ion.}$$

$$\text{Hydrogen is not a fraction of crude oil but a separate element often obtained industrially.}$$

$$\text{Lead tetraethyl reduces knocking in engines by stabilizing combustion, but it is now less used due to toxicity.}$$

$$\text{1 mole of any substance contains Avogadro’s number of particles; 24g of Mg equals 1 mole.}$$

$$\text{Iron is made the cathode in cathodic protection, preventing its oxidation by attracting electrons.}$$

$$\text{The acid reacts with iron oxides (rust), reducing them and leaving clean metallic iron.}$$

$$\text{Sulfur creates cross-links in rubber, enhancing its elasticity and durability.}$$

$$\text{Their d-orbitals allow for variable oxidation states and unique chemical properties.}$$

$$\text{Losing 1 electron creates a metallic ion (cation), typical for Group I elements like Na.}$$

$$\text{A catalyst lowers activation energy, enabling faster reactions without being consumed.}$$

$$\text{Displacement means M is more electropositive than Zn, so it replaces Zn in the compound.}$$

$$\text{Using Faraday’s law: Q = n × F × z, with n as moles of Cu and z = 2 (valency).}$$

$$\text{CH}_3\text{COOH is ethanoic acid, and CH}_2=CH}_2\text{ is ethene (alkene group).}$$

$$\text{Water has stronger intermolecular hydrogen bonds compared to methanol, increasing boiling point.}$$

$$\text{A neutron increases mass number by 1 without altering atomic number.}$$

$$\text{Powdering solids, increasing temperature, and lowering activation energy increase reaction rates by providing more energy and surface area.}$$

$$\text{Magnesium (atomic number 12) has 2 valence electrons and forms divalent ionic bonds.}$$

$$\text{Atomic radius decreases across a period due to increased nuclear charge pulling electrons closer.}$$

$$\text{Applying ideal gas law corrections for temperature and pressure gives the new volume.}$$

$$\text{Oxygen in air reacts with CO to form CO}_2\text{; remaining oxygen is the excess reactant.}$$

$$\text{The simplest ratio of atoms in CH}_3\text{COOH is CH}_2\text{O.}$$