2017 JAMB CHEMISTRY PAST QUESTIONS AND ANSWERS Leave a Comment / Jamb Chemistry / By Jamb Tutor Report a question What’s wrong with this question? You cannot submit an empty report. Please add some details. 0% Created by Jamb TutorJamb Chemistry 2017 JAMB CHEMISTRY PAST QUESTIONS AND ANSWERS 1 / 40 Category: Jamb Chemistry 2017 1. What flame is used by welders for cutting metals? a) Butane gas flame. b) Acetylene flame. c) Kerosene flame. d) Oxy-acetylene flame. The oxy-acetylene flame burns at a high temperature, making it suitable for welding and cutting metals. 2 / 40 Category: Jamb Chemistry 2017 2. At room temperature, solubility comparison in Fig. 1 shows? a) Y is twice as soluble as X. b) X is twice as soluble as Y. c) X and Y are equally soluble. d) X is three times as soluble as Y. Y is observed to be twice as soluble as X in the provided solubility data. 3 / 40 Category: Jamb Chemistry 2017 3. Calculate enthalpy change for ${SO}_3(g) + H_2O(l) \to H_2SO_4(l)$ a) -1032 KJ. b) -130 KJ. c) +130 KJ. d) +1032 KJ. Using enthalpy of formation values, ΔH = ΣH(products) – ΣH(reactants). ΔH = (-811) – [(-395) + (-286)]. 4 / 40 Category: Jamb Chemistry 2017 4. What law is demonstrated by the data for Y and Z? a) Multiple proportions. b) Conservation of mass. c) Constant composition. d) Reciprocal proportion. The data showing multiple ratios of elements between Y and Z corresponds to the law of multiple proportions. 5 / 40 Category: Jamb Chemistry 2017 5. Identify the correct nuclear equation when neutrons bombard an element. a) ${y}z X + n^0 \to y-1{z+1}X$ b) ${y}z X + n^0 \to y+1{z}X$ c) ${y}z X + n^0 \to y{z+1}X$ d) ${y}z X + n^0 \to y+1{z+1}X$ The correct equation shows an increase in mass number (neutron addition) without altering the atomic number. 6 / 40 Category: Jamb Chemistry 2017 6. Vapour density of a gas is defined as? a) Mass vs. water vapour. b) Mass vs. hydrogen. c) Mass vs. oxygen. d) Mass minus vapour pressure. Vapour density compares the mass of a gas to hydrogen under the same conditions. 7 / 40 Category: Jamb Chemistry 2017 7. What is the new pressure if oxygen expands to 20${dm}^3$ from 30${cm}^3$ at 10 atm? a) 6.7 atm. b) 15.0 atm. c) 60.0 atm. d) 66.0 atm. Using Boyle’s Law, P1V1 = P2V2, the pressure is recalculated for the expanded volume. 8 / 40 Category: Jamb Chemistry 2017 8. When does a liquid boil? a) Vapour pressure matches solid. b) Molecules escape surface. c) Vapour equals atmospheric pressure. d) Volume slightly increases. Boiling occurs when vapour pressure of a liquid equals atmospheric pressure, enabling free vaporization. 9 / 40 Category: Jamb Chemistry 2017 9. Which element among W, X, Y, Z is a metal (atomic numbers 2, 6, 16, 20)? a) X. b) W. c) Z. d) Y. Element Z (atomic number 20) is calcium, a Group II metal. 10 / 40 Category: Jamb Chemistry 2017 10. What happens to an electrometer struck by cathode rays? a) Negatively charged. b) Positively charged. c) Neutral. d) Bipolar. Cathode rays consist of electrons, imparting a negative charge upon contact with the electrometer. 11 / 40 Category: Jamb Chemistry 2017 11. What process involves heating hydrocarbons to form smaller molecules? a) Disintegration. b) Polymerization. c) Cracking. d) Degradation. Cracking breaks large hydrocarbon molecules into smaller ones, often for fuel production. 12 / 40 Category: Jamb Chemistry 2017 12. In reaction of sulphuric acid with sugar, it acts as? a) Drying agent. b) Oxidizing agent. c) Dehydrating agent. d) Reducing agent. The sulphuric acid removes water from sugar, acting as a dehydrating agent. 13 / 40 Category: Jamb Chemistry 2017 13. What is the composition of smoke? a) Solid in liquid. b) Solid in gas. c) Gas in liquid. d) Liquid in liquid. Smoke consists of solid or liquid particles dispersed in a gas medium. 14 / 40 Category: Jamb Chemistry 2017 14. Electrolysis of dilute ${H_2SO_4}$: products at cathode and anode? a) Sulphur, Hydrogen. b) Hydrogen, Oxygen. c) Oxygen, Hydrogen. d) Hydrogen, Sulphate. At the cathode, hydrogen is released; oxygen is released at the anode during electrolysis of ${H_2SO_4}$. 15 / 40 Category: Jamb Chemistry 2017 15. How to increase yield of R in reaction P(g) + Q(g) ⇋ 3R(s) + S(g)? a) Larger vessel. b) Higher temperature. c) Remove some S. d) Positive catalyst. Removing S shifts equilibrium to favor product formation (Le Chatelier’s Principle). 16 / 40 Category: Jamb Chemistry 2017 16. What is the mass of silver deposited with 10A in 4830s? a) 108.0g. b) 54.0g. c) 27.0g. d) 13.5g. Using Q = It and molar mass of silver, calculate mass from moles of electrons deposited. 17 / 40 Category: Jamb Chemistry 2017 17. Calculate ΔH for CO(g) + ${H_2O(g)} \to {CO_2(g)} + {H_2(g)}$ a) -282 KJ/mol. b) -42 KJ/mol. c) +42 KJ/mol. d) +262 KJ/mol. Use ΔH = ΣH(products) – ΣH(reactants). Data provided: CO2 = -394 KJ, H2O = -242 KJ, CO = -110 KJ. 18 / 40 Category: Jamb Chemistry 2017 18. How many unpaired electrons in ${1s^2 2s^2 2p^5}$? a) 2 b) 5 c) 1 d) 4 Fluorine’s electron configuration has 5 electrons in p-orbital, with 1 unpaired. 19 / 40 Category: Jamb Chemistry 2017 19. Which gases demonstrate the fountain experiment? a) (ii) and (iii). b) (i) and (iii). c) (ii) and (iv). d) (ii) only. Ammonia and hydrogen chloride react in the fountain experiment due to solubility and pressure changes. 20 / 40 Category: Jamb Chemistry 2017 20. Why are transition metals colored? a) f-orbital. b) s-orbital. c) p-orbital. d) d-orbital. Color results from d-orbital electron transitions absorbing specific light wavelengths. 21 / 40 Category: Jamb Chemistry 2017 21. Which separation process yields ≥ 95% ethanol from palm wine? a) Without dehydrant. b) Simple distillation. c) Fractional distillation. d) Column chromatography. Fractional distillation with a dehydrant efficiently separates ethanol due to its volatility. 22 / 40 Category: Jamb Chemistry 2017 22. Products from hydrolysis of esters? a) Ether and acid. b) Alcohol and acid. c) Ketone and water. d) Alcohol and water. Esters hydrolyze into an alcohol and a carboxylic acid, breaking ester bonds. 23 / 40 Category: Jamb Chemistry 2017 23. Electrons transferred in 3CuO + ${2NH_3}$ a) ${4.0 x 10^{-23}}$ b) ${3.0 x 10^{-23}}$ c) ${1.2 x 10^{24}}$ d) ${6.0 x 10^{24}}$ Each mole of copper involves electron transfer calculated from stoichiometric coefficients. 24 / 40 Category: Jamb Chemistry 2017 24. Unpaired electrons in ${1s^2 2s^2 2p^6 3s^2 3p^3}$? a) 5 b) 4 c) 3 d) 2 Element configuration reveals 3 unpaired electrons in its p-orbital. 25 / 40 Category: Jamb Chemistry 2017 25. Correct reaction for X + ${CuSO_4}$ a) X(s) + ${CuSO_4}$(aq). b) 2X(s) + ${CuSO_4}$(aq). c) ${XSO_4}$(aq). d) 3Cu(s). Equation balancing shows correct stoichiometry between X and ${CuSO_4}$ reacting. 26 / 40 Category: Jamb Chemistry 2017 26. Why use coke in blast furnace? a) Reduce steel. b) Earth impurities. c) Steel formation. d) Calcium carbonate decomposes. Coke reduces iron oxides to iron and reacts with limestone to remove impurities. 27 / 40 Category: Jamb Chemistry 2017 27. Bond between atoms Y and Z? a) Ionic bond. b) Covalent bond. c) Dative bond. d) Metallic bond. Electron sharing forms covalent bonds between non-metals. 28 / 40 Category: Jamb Chemistry 2017 28. Gas expands: final-to-initial temperature ratio? a) 3:01 b) 5:02 c) 5:04 d) 8:03 Using ideal gas law, temperature ratio equals volume ratio at constant pressure. 29 / 40 Category: Jamb Chemistry 2017 29. Chemical for coagulation in water purification? a) Aluminium sulfate. b) Copper sulfate. c) Sodium sulfate. d) Calcium sulfate. Aluminium tetraoxosulphate(VI) facilitates coagulation by clumping impurities. 30 / 40 Category: Jamb Chemistry 2017 30. What dissolves fats? a) HCl acid. b) Calcium hydroxide. c) Kerosene. d) Water. Kerosene dissolves non-polar fats due to similar molecular structures. 31 / 40 Category: Jamb Chemistry 2017 31. What gases remain after alkaline pyrogallol absorption? a) Nitrogen and ${CO_2}$. b) Rare gases. c) Nitrogen and oxygen. d) Nitrogen and rare gases. Alkaline pyrogallol absorbs oxygen; remaining gases are nitrogen and rare gases. 32 / 40 Category: Jamb Chemistry 2017 32. Number of atoms in one mole of a substance equals? a) Atomic number. b) Avogadro number. c) Gas constant. d) Number of electrons. Avogadro’s number defines the number of atoms or molecules in one mole. 33 / 40 Category: Jamb Chemistry 2017 33. What indicates number of bonds atom forms? a) Oxidation number. b) Valence. c) Atomic number. d) Electronegativity. Valence reflects the number of electrons available for bonding in an atom. 34 / 40 Category: Jamb Chemistry 2017 34. What is the structural formula of ethanoic acid? a) ${CH_4}$. b) ${CH_3OH}$. c) ${CH_3CO}$. d) ${CH_3COOH}$. Ethanoic acid (acetic acid) has the formula ${CH_3COOH}$, containing carboxylic (-COOH) group. 35 / 40 Category: Jamb Chemistry 2017 35. What worsens pollution from car exhaust? a) Water vapor. b) Steam. c) Smoke. d) Heavy metals. Exhaust releases heavy metals like lead and hydrocarbons causing severe environmental effects. 36 / 40 Category: Jamb Chemistry 2017 36. Volume of 0.5M ${H_2SO_4}$ neutralizing ${20cm^3}$ of NaOH? a) ${2.0 cm^3}$. b) ${5.0 cm^3}$. c) ${6.8 cm^3}$. d) ${8.3 cm^3}$. Using ${M_1V_1 = M_2V_2}$, solve for ${H_2SO_4}$ volume at 0.5M to neutralize. 37 / 40 Category: Jamb Chemistry 2017 37. Which substance is an electrolyte? a) Alcohol. b) Sodium acetate. c) Solid KOH. d) Mercury. Sodium acetate in solution conducts electricity, qualifying as an electrolyte. 38 / 40 Category: Jamb Chemistry 2017 38. Reaction to increase rate: ${Na_2S_2O_3}$ + HCl? a) Low temp, low conc. b) Low volume, high P. c) Low temp, high conc. d) High temp, high conc. Higher temperature and concentration accelerate this reaction’s rate due to increased molecular collisions. 39 / 40 Category: Jamb Chemistry 2017 39. Which substance has the lowest vapor density? a) Ethanoic acid. b) Propanol. c) Dichloromethane. d) Ethanal. Ethanal has the lowest molar mass among choices, leading to lowest vapor density. 40 / 40 Category: Jamb Chemistry 2017 40. How does impurity affect melting point? a) Stable. b) Reduced. c) Increased. d) Zero. Impurities disrupt lattice structures, reducing melting points in crystalline solids. 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