Chemistry, 2018, JAMB Exam, Exam, Paper 1 | Objectives

Paper Info

Year :

2018

Title :

Chemistry

Exam :

JAMB Exam

Paper 1 | Objectives

71 - 80 of 87 Questions

#	Question	Ans
71.	The ionic radii of metals are usually A. greater than their atomic radii B. unaffected by the charge on the ion C. the same as their atomic radii D. less than their atomic radii Show Content Detailed Solution In a neutral atom, the atomic and ionic radius is the same, but many elements exist as anions or cations. If the atom loses its outermost electron (positively charged or cation), the ionic radius is smaller than the atomic radius because the atom loses an electron energy shell. Yes ionic radius is only less than atomic radius for a metal. There is an explanation video available below.	D
72.	Calculate the percentage composition of oxygen in calcium trioxocarbonate(IV) [Ca=40, C=12, O=16] A. 16 B. 48 C. 40 D. 12 Show Content Detailed Solution Calcium trioxocarbonate (IV) = CaCO\(_3\) Percentage of Oxygen = \(\frac{\text{Molar mass of 3O}}{\text{Molar mass of} CaCO_3}\) × 100% Percentage of Oxygen = \(\frac{(3 \times 16)}{(40 + 12 + 48)}\) x 100% Percentage of Oxygen = \(\frac{48}{100}\) x 100% Percentage of Oxygen = 48% There is an explanation video available below.	B
73.	Which of these alloys contains copper? A. solder B. steel C. permallory D. bronze Show Content Detailed Solution Bronze is an alloy consisting primarily of copper, commonly with about 12% tin and often with the addition of other metals (such as aluminium, manganese, nickel or zinc) and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon. There is an explanation video available below.	D
74.	If the molecular mass of tetraoxosulphate (VI) acid is 98, calculate its vapour density. A. 196 B. 49 C. 106 D. 82 Show Content Detailed Solution Molecular mass = Vapour Density x 2 Vapour Density = \(\frac{\text{Molecular Mass}}{2}\) Where Molecular mass = 98g/mol Vapour Density = \(\frac{98}{2}\) Vapour Density = 49g/mol There is an explanation video available below.	B
75.	Sieving is a technique used to separate mixtures containing solid particles of A. small sizes B. large sizes C. different sizes D. the same size Show Content Detailed Solution Sieving is a simple and convenient technique of separating particles of different sizes. There is an explanation video available below.	C
76.	3H\(_{2(g)}\)+ N\(_{2(g)}\)⇔ 2NH\(_{3(g)}\) ; H= -ve In the reaction above, lowering of temperature will A. have no effect on the equilibrium position B. increase the rate of both the forward and reverse reactions equally C. favour the forward reaction D. favour the reverse reaction Show Content Detailed Solution N\(_{2(g)}\) + 3H\(_{2(g)}\) ⇔ 2NH\(_{3(g)}\) In the Haber process, the forward reaction is exothermic and the backward reaction is endothermic. If the temperature is decreased, the yield from the exothermic direction is increased i.e. the forward reaction is increased. There is an explanation video available below.	C
77.	The situation obtained when a perfect gas expands into a vacuum is A. ΔH is positive and TΔ S is zero B. ΔH is positive and T Δ S is negative C. ΔH is negative and TΔ S is zero D. ΔH is zero and T Δ S is positive Show Content Detailed Solution The definition of enthalpy change is ΔH = ΔU + Pex(ΔV) The enthalpy change is zero because both terms on the right are zero in free expansion of an ideal gas. There is no external pressure in a free expansion, so P (ex) = 0. And the internal energy change, ΔU of free expansion in a closed system is zero since no inter molecular forces have to be overcome. The temperature remains constant and no heat is absorbed or released. There is an explanation video available below.	D
78.	The general formula of alkanones is A. RCHO B. R\(_2\)CO C. RCOOH D. RCOOR Show Content Detailed Solution Alkanones also known as ketones have the general formula R\(_2\)CO There is an explanation video available below.	B
79.	The alkanoic acid found in human sweat is A. CH\(_3\)-COOH B. CH\(_3\)—CH\(_2\)—COOH C. H-COOH D. CH\(_3\) Show Content Detailed Solution Bacteria of the genus Propionibacterium produce propionic acid (Propanoic Acid) as the end-product of their anaerobic metabolism. This class of bacteria is commonly found in the stomach of ruminants and the sweat glands of humans, and their activity is partially responsible for the odour of both Swiss cheese and sweat. There is an explanation video available below.	B
80.	The elements in the periodic table are listed in order of increasing A. relative atomic number B. atomic mass C. relative isotopic mass D. nuclear charge Show Content Detailed Solution The periodic number table is arranged in order of atoms increasing atomic number There is an explanation video available below.	A

71.	The ionic radii of metals are usually A. greater than their atomic radii B. unaffected by the charge on the ion C. the same as their atomic radii D. less than their atomic radii Show Content Detailed Solution In a neutral atom, the atomic and ionic radius is the same, but many elements exist as anions or cations. If the atom loses its outermost electron (positively charged or cation), the ionic radius is smaller than the atomic radius because the atom loses an electron energy shell. Yes ionic radius is only less than atomic radius for a metal. There is an explanation video available below.	D
72.	Calculate the percentage composition of oxygen in calcium trioxocarbonate(IV) [Ca=40, C=12, O=16] A. 16 B. 48 C. 40 D. 12 Show Content Detailed Solution Calcium trioxocarbonate (IV) = CaCO\(_3\) Percentage of Oxygen = \(\frac{\text{Molar mass of 3O}}{\text{Molar mass of} CaCO_3}\) × 100% Percentage of Oxygen = \(\frac{(3 \times 16)}{(40 + 12 + 48)}\) x 100% Percentage of Oxygen = \(\frac{48}{100}\) x 100% Percentage of Oxygen = 48% There is an explanation video available below.	B
73.	Which of these alloys contains copper? A. solder B. steel C. permallory D. bronze Show Content Detailed Solution Bronze is an alloy consisting primarily of copper, commonly with about 12% tin and often with the addition of other metals (such as aluminium, manganese, nickel or zinc) and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon. There is an explanation video available below.	D
74.	If the molecular mass of tetraoxosulphate (VI) acid is 98, calculate its vapour density. A. 196 B. 49 C. 106 D. 82 Show Content Detailed Solution Molecular mass = Vapour Density x 2 Vapour Density = \(\frac{\text{Molecular Mass}}{2}\) Where Molecular mass = 98g/mol Vapour Density = \(\frac{98}{2}\) Vapour Density = 49g/mol There is an explanation video available below.	B
75.	Sieving is a technique used to separate mixtures containing solid particles of A. small sizes B. large sizes C. different sizes D. the same size Show Content Detailed Solution Sieving is a simple and convenient technique of separating particles of different sizes. There is an explanation video available below.	C

76.	3H\(_{2(g)}\)+ N\(_{2(g)}\)⇔ 2NH\(_{3(g)}\) ; H= -ve In the reaction above, lowering of temperature will A. have no effect on the equilibrium position B. increase the rate of both the forward and reverse reactions equally C. favour the forward reaction D. favour the reverse reaction Show Content Detailed Solution N\(_{2(g)}\) + 3H\(_{2(g)}\) ⇔ 2NH\(_{3(g)}\) In the Haber process, the forward reaction is exothermic and the backward reaction is endothermic. If the temperature is decreased, the yield from the exothermic direction is increased i.e. the forward reaction is increased. There is an explanation video available below.	C
77.	The situation obtained when a perfect gas expands into a vacuum is A. ΔH is positive and TΔ S is zero B. ΔH is positive and T Δ S is negative C. ΔH is negative and TΔ S is zero D. ΔH is zero and T Δ S is positive Show Content Detailed Solution The definition of enthalpy change is ΔH = ΔU + Pex(ΔV) The enthalpy change is zero because both terms on the right are zero in free expansion of an ideal gas. There is no external pressure in a free expansion, so P (ex) = 0. And the internal energy change, ΔU of free expansion in a closed system is zero since no inter molecular forces have to be overcome. The temperature remains constant and no heat is absorbed or released. There is an explanation video available below.	D
78.	The general formula of alkanones is A. RCHO B. R\(_2\)CO C. RCOOH D. RCOOR Show Content Detailed Solution Alkanones also known as ketones have the general formula R\(_2\)CO There is an explanation video available below.	B
79.	The alkanoic acid found in human sweat is A. CH\(_3\)-COOH B. CH\(_3\)—CH\(_2\)—COOH C. H-COOH D. CH\(_3\) Show Content Detailed Solution Bacteria of the genus Propionibacterium produce propionic acid (Propanoic Acid) as the end-product of their anaerobic metabolism. This class of bacteria is commonly found in the stomach of ruminants and the sweat glands of humans, and their activity is partially responsible for the odour of both Swiss cheese and sweat. There is an explanation video available below.	B
80.	The elements in the periodic table are listed in order of increasing A. relative atomic number B. atomic mass C. relative isotopic mass D. nuclear charge Show Content Detailed Solution The periodic number table is arranged in order of atoms increasing atomic number There is an explanation video available below.	A

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