Year :
2020
Title :
Chemistry
Exam :
WASSCE/WAEC MAY/JUNE
Paper 1 | Objectives
31 - 40 of 49 Questions
| # | Question | Ans |
|---|---|---|
| 31. |
When 250 cm3 of a saturated solution of CuSO\(_4\) at 30°C was evaporated to dryness, 5.0 g of the salt was obtained..What is the solubility of the salt at 30°C? [CuSO\(_4\) = 160] A. 0.031 B. 0.125 C. 0.640 D. 1.560 |
B |
| 32. |
The bond between NH\(_3\) and H\(^+\) in NH4\(^+\) is? A. dative B. covalent C. hydrogen D. electrovalent |
A |
| 33. |
Which of the following oxides has a giant covalent structure? A. Al\(_2\)O\(_3\) B. Na\(_2\)O C. P\(_4\)O\(_10\) D. SiO\(_2\) Detailed Solution- Silicon dioxide is an example of a substance with a giant covalent structure . It contains many silicon and oxygen atoms. All the atoms in its structure are linked to each other by strong covalent bonds. The atoms are joined to each other in a regular arrangement, forming a giant covalent structure. |
|
| 34. |
Which of the following hydroxides is not readily soluble in water? A. NH\(_4\)OH B. Ca(OH)\(_2\) C. NaOH D. KOH Detailed Solution-The hydroxides of sodium, potassium, and ammonium are very soluble in water. The hydroxides of calcium and barium are moderately soluble. |
|
| 35. |
Which of the following statements about the solubility of a salt is correct? A. A salt whose solubility increases with temperature would not crystallize easily on cooling B. A salt whose solubility is independent of temperature would normally crystallize out on cooling C. Crystallization would be efficient in separating out a salt whose solubility increases considerably with temperature D. Solubility of a solid does not affect its crystallization Detailed SolutionCrystallization is based on the principles of solubility: compounds (solutes) tend to be more soluble in hot liquids (solvents) than they are in cold liquids. If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound. |
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| 36. |
How many moles of H\(_2\)SO4 are there in 50 cm\(^3\) of 0.108 mol dm\(^3\) solution of the acid? A. 5.4x 10 B. 5.4 x 10\(^-3\) C. 5.4 x 10\(^-2\) D. 5.4x 10\(^-1\) Detailed SolutionNo. of moles = ( molar conc X volume ) / 1000No. of moles = 0.108 X 50 / 1000 : No. of moles = 0.0054 moles |
|
| 37. |
If 20 cm\(^3\) of sodium hydroxide was neutralized by 20 cm\(^3\) of 0.01 mol dm3 tetraoxosulphate(VI) acid, what is the concentration of the solution? A. 0.010 B. 0.020 C. 0.100 D. 0.150 Detailed Solution\(frac{CaVa}{CbVb}\) = \(frac{Na}{Nb}\)( 0.01 X 20 ) / (Cb X 20) = 1 / 2 cross multiply → Cb = (0.01 X 20 X 2) / ( 20 X 1) Cb = 0.02 mol/dm\(^3\) |
|
| 38. |
"Electrons always occupy the lowest empty energy level" is a statement of A. Aufbau Principle B. Hund's rule C. Pauli Exclusion Principle D. Periodic law Detailed Solution- The Aufbau principle states that electrons fill lower-energy atomic orbitals before filling higher-energy ones |
|
| 39. |
Which of the following metals does not react with water to produce hydrogen? A. Copper B. Potassium C. Sodium D. Zinc Detailed SolutionMost alkali metals and alkaline earth metals react with water to produce hydrogen. The alkali metals comprise Group 1 of the periodic table, and include lithium, sodium, potassium, etc. - Zinc is not much reactive with cold or room temperature water but reacts with steam to form zinc oxide and liberate hydrogen gas. - Copper lies below hydrogen in the activity series of metals, therefore it can not displace hydrogen from water |
|
| 40. |
Which of the following arrangement of elements is in decreasing order of electronegativity? A. Na, Mg, Al, Si, P B. Na, A1, Mg, P, Si C. P, Mg, Na, Si, Al D. P, Si, Al, Mg, Na Detailed Solution- Reactivity series is K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au.-Very Electropositive Metals Most active metals have low electronegativities |
| 31. |
When 250 cm3 of a saturated solution of CuSO\(_4\) at 30°C was evaporated to dryness, 5.0 g of the salt was obtained..What is the solubility of the salt at 30°C? [CuSO\(_4\) = 160] A. 0.031 B. 0.125 C. 0.640 D. 1.560 |
B |
| 32. |
The bond between NH\(_3\) and H\(^+\) in NH4\(^+\) is? A. dative B. covalent C. hydrogen D. electrovalent |
A |
| 33. |
Which of the following oxides has a giant covalent structure? A. Al\(_2\)O\(_3\) B. Na\(_2\)O C. P\(_4\)O\(_10\) D. SiO\(_2\) Detailed Solution- Silicon dioxide is an example of a substance with a giant covalent structure . It contains many silicon and oxygen atoms. All the atoms in its structure are linked to each other by strong covalent bonds. The atoms are joined to each other in a regular arrangement, forming a giant covalent structure. |
|
| 34. |
Which of the following hydroxides is not readily soluble in water? A. NH\(_4\)OH B. Ca(OH)\(_2\) C. NaOH D. KOH Detailed Solution-The hydroxides of sodium, potassium, and ammonium are very soluble in water. The hydroxides of calcium and barium are moderately soluble. |
|
| 35. |
Which of the following statements about the solubility of a salt is correct? A. A salt whose solubility increases with temperature would not crystallize easily on cooling B. A salt whose solubility is independent of temperature would normally crystallize out on cooling C. Crystallization would be efficient in separating out a salt whose solubility increases considerably with temperature D. Solubility of a solid does not affect its crystallization Detailed SolutionCrystallization is based on the principles of solubility: compounds (solutes) tend to be more soluble in hot liquids (solvents) than they are in cold liquids. If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound. |
| 36. |
How many moles of H\(_2\)SO4 are there in 50 cm\(^3\) of 0.108 mol dm\(^3\) solution of the acid? A. 5.4x 10 B. 5.4 x 10\(^-3\) C. 5.4 x 10\(^-2\) D. 5.4x 10\(^-1\) Detailed SolutionNo. of moles = ( molar conc X volume ) / 1000No. of moles = 0.108 X 50 / 1000 : No. of moles = 0.0054 moles |
|
| 37. |
If 20 cm\(^3\) of sodium hydroxide was neutralized by 20 cm\(^3\) of 0.01 mol dm3 tetraoxosulphate(VI) acid, what is the concentration of the solution? A. 0.010 B. 0.020 C. 0.100 D. 0.150 Detailed Solution\(frac{CaVa}{CbVb}\) = \(frac{Na}{Nb}\)( 0.01 X 20 ) / (Cb X 20) = 1 / 2 cross multiply → Cb = (0.01 X 20 X 2) / ( 20 X 1) Cb = 0.02 mol/dm\(^3\) |
|
| 38. |
"Electrons always occupy the lowest empty energy level" is a statement of A. Aufbau Principle B. Hund's rule C. Pauli Exclusion Principle D. Periodic law Detailed Solution- The Aufbau principle states that electrons fill lower-energy atomic orbitals before filling higher-energy ones |
|
| 39. |
Which of the following metals does not react with water to produce hydrogen? A. Copper B. Potassium C. Sodium D. Zinc Detailed SolutionMost alkali metals and alkaline earth metals react with water to produce hydrogen. The alkali metals comprise Group 1 of the periodic table, and include lithium, sodium, potassium, etc. - Zinc is not much reactive with cold or room temperature water but reacts with steam to form zinc oxide and liberate hydrogen gas. - Copper lies below hydrogen in the activity series of metals, therefore it can not displace hydrogen from water |
|
| 40. |
Which of the following arrangement of elements is in decreasing order of electronegativity? A. Na, Mg, Al, Si, P B. Na, A1, Mg, P, Si C. P, Mg, Na, Si, Al D. P, Si, Al, Mg, Na Detailed Solution- Reactivity series is K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au.-Very Electropositive Metals Most active metals have low electronegativities |