Chemistry, 2009, JAMB Exam, Exam, Paper 1 | Objectives

Paper Info

Year :

2009

Title :

Chemistry

Exam :

JAMB Exam

Paper 1 | Objectives

21 - 30 of 50 Questions

#	Question	Ans
21.	The oxidation state of Cr in K\(_2\)Cr\(_2\)O\(_7\) is? A. +7 B. +6 C. +5 D. 4 Show Content Detailed Solution Potassium dichromate, K\(_2\)Cr\(_2\)O\(_7\) → [1 * 2] + [Cr * 2] + [-2 * 7] = 0 → 2 + 2Cr - 14 = 0 → 2Cr = 12 →Cr = \(\frac{12}{2}\) → 6 There is an explanation video available below.	B
22.	Which of the following metals is purified commercially by electrolysis? A. Zn B. Fe C. Sn D. Cu Show Content Detailed Solution Electrolysis is used extensively in metallurgical processes, such as in extraction (electrowinning) or purification (electrorefining) of metals from ores or compounds and in deposition of metals from solution (electroplating). Copper is purified by electrolysis . Electricity is passed through solutions containing copper compounds, such as copper(II) sulfate. There is an explanation video available below.	D
23.	What current will deposit 3.25g of zinc in 2hrs? [Zn = 65, F = 96500 mol^-] A. 3.25A B. 2.00A C. 1.34A D. 0.67A Show Content Detailed Solution There is an explanation video available below.	C
24.	C(s) + H2O(g) → H2(g) + CO2(g) ΔG for the reaction above at 1300k is -43KJ. At this temperature, the reaction is? A. not feasible B. at equilibrium C. feasible D. exothermic Show Content Detailed Solution For a reaction to be feasible, ΔG has to be negative. There is an explanation video available below.	C
25.	Two equal bulbs, one containing ammonia and the other nitrogen are opened mouth - to - mouth to each other at room temperature. The entropy in the mixture of gases is likely to? A. remain unchange B. increase C. decrease D. change Show Content Detailed Solution When two or more gases are mixed together at constant volume, there is an increase in entropy. There is an explanation video available below.	B
26.	In the diagram above, which of the curves represents the evolution of oxygen with time in the equation 2KClO3(s) → 2KCl(s) + 3O2(g)? A. X B. Y C. Z D. R Show Content Detailed Solution There is an explanation video available below.	D
27.	A catalyst increase the rate of a chemical reaction by providing a path that? A. raise the activiation energy B. increase the temperature C. lowers the activation energy D. increase the concentration Show Content Detailed Solution The rate of a reaction can be increased by adding a suitable catalyst. A catalyst is a substance which increases the rate of a chemical reaction but it is not used up (remains chemically unchanged at the end). It provides an alternative reaction pathway of lower activation energy. There is an explanation video available below.	C
28.	CuO(s) + H\(_2\)(g) ↔ Cu(s) + H\(_2\)O(g) What is the effect of increasing the pressure on the equilibrium reaction above? A. The equilibrium is shifted to the left B. The equilibrium is shifted to the right C. There is no effect D. More H_2(g) is produced Show Content Detailed Solution When amount / volume of gaseous reactants equal amount / volume of gaseous products, the change in pressure has no effect on the equilibrium position. There is an explanation video available below.	C
29.	The equilibrium of an endothermic reaction which proceeds with an increase in volume can be shifted in the reverse direction by A. increasing the temperature and decreasing the pressure B. increasing the pressure and increasing the temperature C. decreasing the temperature and increasing the pressure D. decreasing the pressure and decreasing the temperature Show Content Detailed Solution There is an explanation video available below.	C
30.	The oxidation of ammonia in excess air produces? A. NO B. N₂O C. NO₂ D. N₂O₄ Show Content Detailed Solution In the presence of heated platinum catalyst, ammonia reacts with excess air to produce nitrogen (II) oxide, NO, (instead of nitrogen) and water. There is an explanation video available below.	A

21.	The oxidation state of Cr in K\(_2\)Cr\(_2\)O\(_7\) is? A. +7 B. +6 C. +5 D. 4 Show Content Detailed Solution Potassium dichromate, K\(_2\)Cr\(_2\)O\(_7\) → [1 * 2] + [Cr * 2] + [-2 * 7] = 0 → 2 + 2Cr - 14 = 0 → 2Cr = 12 →Cr = \(\frac{12}{2}\) → 6 There is an explanation video available below.	B
22.	Which of the following metals is purified commercially by electrolysis? A. Zn B. Fe C. Sn D. Cu Show Content Detailed Solution Electrolysis is used extensively in metallurgical processes, such as in extraction (electrowinning) or purification (electrorefining) of metals from ores or compounds and in deposition of metals from solution (electroplating). Copper is purified by electrolysis . Electricity is passed through solutions containing copper compounds, such as copper(II) sulfate. There is an explanation video available below.	D
23.	What current will deposit 3.25g of zinc in 2hrs? [Zn = 65, F = 96500 mol^-] A. 3.25A B. 2.00A C. 1.34A D. 0.67A Show Content Detailed Solution There is an explanation video available below.	C
24.	C(s) + H2O(g) → H2(g) + CO2(g) ΔG for the reaction above at 1300k is -43KJ. At this temperature, the reaction is? A. not feasible B. at equilibrium C. feasible D. exothermic Show Content Detailed Solution For a reaction to be feasible, ΔG has to be negative. There is an explanation video available below.	C
25.	Two equal bulbs, one containing ammonia and the other nitrogen are opened mouth - to - mouth to each other at room temperature. The entropy in the mixture of gases is likely to? A. remain unchange B. increase C. decrease D. change Show Content Detailed Solution When two or more gases are mixed together at constant volume, there is an increase in entropy. There is an explanation video available below.	B

26.	In the diagram above, which of the curves represents the evolution of oxygen with time in the equation 2KClO3(s) → 2KCl(s) + 3O2(g)? A. X B. Y C. Z D. R Show Content Detailed Solution There is an explanation video available below.	D
27.	A catalyst increase the rate of a chemical reaction by providing a path that? A. raise the activiation energy B. increase the temperature C. lowers the activation energy D. increase the concentration Show Content Detailed Solution The rate of a reaction can be increased by adding a suitable catalyst. A catalyst is a substance which increases the rate of a chemical reaction but it is not used up (remains chemically unchanged at the end). It provides an alternative reaction pathway of lower activation energy. There is an explanation video available below.	C
28.	CuO(s) + H\(_2\)(g) ↔ Cu(s) + H\(_2\)O(g) What is the effect of increasing the pressure on the equilibrium reaction above? A. The equilibrium is shifted to the left B. The equilibrium is shifted to the right C. There is no effect D. More H_2(g) is produced Show Content Detailed Solution When amount / volume of gaseous reactants equal amount / volume of gaseous products, the change in pressure has no effect on the equilibrium position. There is an explanation video available below.	C
29.	The equilibrium of an endothermic reaction which proceeds with an increase in volume can be shifted in the reverse direction by A. increasing the temperature and decreasing the pressure B. increasing the pressure and increasing the temperature C. decreasing the temperature and increasing the pressure D. decreasing the pressure and decreasing the temperature Show Content Detailed Solution There is an explanation video available below.	C
30.	The oxidation of ammonia in excess air produces? A. NO B. N₂O C. NO₂ D. N₂O₄ Show Content Detailed Solution In the presence of heated platinum catalyst, ammonia reacts with excess air to produce nitrogen (II) oxide, NO, (instead of nitrogen) and water. There is an explanation video available below.	A