WAEC SSCE - Chemistry - 2018 (Objective)

View Answer

Question 4 Report

Particles in a solid exibit

vibrational motion

vibrational and translational motion

vibrational and random motion

random and translational motion

Answer Details

Particles in a solid exhibit vibrational motion. In a solid, the particles are closely packed together and held in a fixed position by strong intermolecular forces. However, the particles are not completely motionless. They can vibrate around their fixed positions due to thermal energy. The amount of energy available for this vibrational motion is determined by the temperature of the solid. As the temperature increases, the particles vibrate more vigorously. However, the particles do not move from their positions in the solid, and so they do not exhibit translational motion. Therefore, the correct answer is that particles in a solid exhibit vibrational motion. The other options (vibrational and translational motion, vibrational and random motion, and random and translational motion) are not correct because they describe the motion of particles in liquids or gases, where the particles are free to move and exhibit translational or random motion in addition to vibrational motion.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

View Answer

Question 5 Report

The atomic number of an isotope of hydrogen is equal to its mass number because it

has a totally filled valence shell

has a high charge to mass ratio

does not contain neutrons

exhibits isotopy

View Answer

Question 6 Report

Which of the following methods can be used to seperate blood cells from plasma?

Centrifugation

Filtration

Chromatography

Distillation

Answer Details

The method that can be used to separate blood cells from plasma is: Centrifugation. Centrifugation is a process of separating components in a mixture based on their density differences. In the case of blood, when it is spun in a centrifuge, the heavier components, such as the blood cells, are forced to the bottom of the tube while the lighter components, such as plasma, stay at the top. The separation is based on the fact that blood cells are denser than plasma. Therefore, centrifugation is the method that can be used to separate blood cells from plasma. Filtration, chromatography, and distillation are other methods of separating mixtures, but they are not suitable for separating blood cells from plasma. Filtration is the process of separating solids from liquids using a filter. Chromatography is a laboratory technique for separating mixtures into their individual components. Distillation is the process of separating components of a mixture based on differences in their boiling points.

Read lesson note on Separation Of Mixtures And Purification Of Chemical Substances (JAMB)

Separation Of Mixtures And Purification Of Chemical Substances

View Answer

Question 7 Report

The diagram above illustrates a conical flask containing water and ice. Which of the following is correct about the diagram?

The water is at lower temperature than the ice

Energy is absorbed when the ice changes to water

Energy is released when the ice changes to water

The water molecules vibrate about a fixed point

Answer Details

The correct statement about the diagram is: "Energy is absorbed when the ice changes to water." When ice changes to water, it undergoes a physical process known as "melting." During this process, energy is absorbed from the surroundings in order to overcome the attractive forces between the ice molecules and break them apart into individual water molecules. This energy is in the form of heat, and it is absorbed from the surroundings, which results in a decrease in temperature. Therefore, the water in the conical flask will be at a lower temperature than the ice after the ice starts melting. The water molecules do vibrate about a fixed point, but this statement is not relevant to the question being asked.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

Read lesson note on States Of Matter (WAEC)

States Of Matter

View Answer

Question 8 Report

What is the solubility of a salt if 0.4g of it is obtained on evaporating 200$cm^{3}$ of its saturated solution to dryness?

0.08$gdm^{-3}$

2.00$gdm^{-3}$

8.00$gdm^{-3}$

80.00$gdm^{-3}$

Solubility

View Answer

Question 9 Report

An organic compound has the empirical formula $CH_{2}$. If its molar mass is 42$gmol^{-1}$, what is its molecular formula? (C = 12.0, H = 1.0)

$C_{2}H_{4}$

$C_{3}H_{4}$

$C_{3}H_{6}$

$C_{4}H_{8}$

Answer Details

The empirical formula of the organic compound is given as $CH_{2}$, which means that the ratio of carbon to hydrogen atoms in the compound is 1:2. The molar mass of the compound is also given as 42$gmol^{-1}$. To find the molecular formula, we need to determine the actual number of carbon and hydrogen atoms in the compound. Let's assume that the molecular formula of the compound is $C_{x}H_{y}$. The molar mass of the compound can be calculated as follows: molar mass = (molar mass of carbon) x (number of carbon atoms) + (molar mass of hydrogen) x (number of hydrogen atoms) 42 = (12.0 g/mol) x (x) + (1.0 g/mol) x (y) Simplifying the equation, we get: 12x + y = 42 However, we also know that the ratio of carbon to hydrogen atoms in the compound is 1:2. This means that: x/y = 1/2 Multiplying both sides by y, we get: x = (1/2)y Substituting this value of x in the previous equation, we get: 12(1/2)y + y = 42 Simplifying the equation, we get: 18y = 42 y = 2.33 Since the number of atoms must be a whole number, we can round y to the nearest whole number, which is 2. This means that the molecular formula of the compound is $C_{x}H_{2}$. Using the ratio of carbon to hydrogen atoms in the empirical formula, we know that x = 2. Therefore, the molecular formula of the compound is $C_{2}H_{4}$. Hence, the answer is option A) $C_{2}H_{4}$.

Read lesson note on Chemistry Of Carbon Compounds (Ghana Only) (WAEC)

Read lesson note on Organic Compounds (JAMB)

Chemistry Of Carbon Compounds (Ghana Only)

Organic Compounds

View Answer

Question 10 Report

In which of the following compounds does hydrogen form ionic compounds?

CH$_{4}$

HCl

NH$_{3}$

NaH

Answer Details

Out of the given compounds, only NaH (sodium hydride) contains ionic bonds involving hydrogen. In NaH, hydrogen has a negative charge (H$^-$) and sodium has a positive charge (Na$^+$). This results in the formation of an ionic compound. In the other compounds, hydrogen forms covalent bonds. In CH$_4$ (methane), hydrogen shares electrons with carbon to form four covalent bonds. In HCl (hydrogen chloride), hydrogen shares electrons with chlorine to form a single covalent bond. In NH$_3$ (ammonia), hydrogen shares electrons with nitrogen to form three covalent bonds. Therefore, only NaH contains ionic bonds involving hydrogen, while the others have covalent bonds.

Read lesson note on Chemical Combination (JAMB)

Chemical Combination

View Answer

Question 11 Report

A reaction is endothermic if the

reaction vessel feels cool during the reaction

enthalpy change is negative

bond forming energy exceeds bond breaking energy

heat of formation of reactants exceeds heat of formation of products

Answer Details

An endothermic reaction is a reaction that requires energy to be absorbed from the surroundings. This means that the reaction absorbs heat and as a result, the surroundings feel cooler. Therefore, the correct option is "reaction vessel feels cool during the reaction". The other options do not necessarily define an endothermic reaction.

Read lesson note on Energy Changes (JAMB)

Read lesson note on Energy And Energy Changes (WAEC)

Energy Changes

Energy And Energy Changes

View Answer

Question 12 Report

How many atoms are contained in 0.2moles of nitrogen? $[N_{A} = 6.02 \times 10^{23}]$

$1.20 \times 10^{23}$

$2.41 \times 10^{23}$

$3.62 \times 10^{23}$

$4.82 \times 10^{23}$

Answer Details

To determine the number of atoms in 0.2 moles of nitrogen, we can use Avogadro's number, which represents the number of particles in one mole of a substance. Avogadro's number is equal to 6.02 x 10^23 particles per mole. First, we need to calculate the number of nitrogen atoms in 0.2 moles of nitrogen. We can do this by multiplying the number of moles by Avogadro's number: 0.2 moles x 6.02 x 10^23 particles/mole = 1.204 x 10^23 particles Therefore, there are 1.204 x 10^23 atoms in 0.2 moles of nitrogen. The answer is $1.20 \times 10^{23}$.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

View Answer

Question 13 Report

When a salt is added to its saturated solution, the salt

dissolves and the solution becomes super saturated

dissolves and the solution becomes unsaturated

precipitates and the solution remains unchanged

dissolves and crystals are formed

Solubility

View Answer

Question 14 Report

The solubility of $CO_{2}$ in water can be accounted for by

Van der Waal's forces

Ionic attraction

dipole attraction

covalent bonding

Solubility

Solubility Of Substances (Ghana Only)

View Answer

Question 15 Report

The strength of metallic bonds depends on the

charge density of the atoms

ductility of the metal

number of valence electrons

total number of electrons in the atom

View Answer

Question 16 Report

Which of the following raw materials is used in the plastic industry?

Ethene

Methane

Sulphur

Hydrogen

Answer Details

In the plastic industry, ethene (also known as ethylene) is commonly used as a raw material. Ethene is a colorless and flammable gas that can be polymerized to produce a wide range of plastics, including polyethylene, which is one of the most widely used plastics in the world. Methane, sulfur, and hydrogen are not typically used as raw materials in the plastic industry.

Read lesson note on Basic Biochemistry And Synthetic Polymers (WAEC)

Basic Biochemistry And Synthetic Polymers

View Answer

Question 17 Report

Which of the following CANNOT be an empirical formula?

$CH$

$CH_{2}$

$P_{2}O_{5}$

$N_{2}O_{4}$

View Answer

Question 18 Report

Stainless steel is an alloy comprising of

Fe and C

Fe and Ni

Fe, C and Ni

Fe, C and Al

Chemical Combination

View Answer

Question 19 Report

Which of the following equations represents a redox reaction?

$HNO_{{3}{(aq)}} + NaOH_{(aq)} \to NaNO_{{3}{(aq)}} + H_{2}O_{(l)}$

$AgNO_{{3}{(aq)}}+KCl_{(aq)} \to AgCl_{(s)}+KNO_{{3}{(aq)}}$

$CaCO_{{3}{(s)}} \to CaO_{(s)} + CO_{{2}{(g)}}$

$2H_{2}S_{(s)} + SO_{{2}{(g)}} \to 2HO_{2} + 3S_{(g)}$

Chemistry Of Carbon Compounds (Ghana Only)

Chemistry, Industry And The Environment

Redox Reactions

View Answer

Question 20 Report

An acidic salt has

double anions in its aqueous solution

a single cation in its aqueous solution

hydrogen ions in its aqueous solution

hydrogen atoms in its aqueous solution

Answer Details

An acidic salt has hydrogen ions in its aqueous solution. When a salt is formed from a weak acid and a strong base, the resulting salt can still contain some of the acidic properties of the original acid. This means that when the salt is dissolved in water, it can release hydrogen ions (H+) into the solution, making it acidic. This is why the salt is called an acidic salt. In contrast, basic salts contain hydroxide ions (OH-) in their aqueous solution.

Read lesson note on Acids, Bases And Salts (JAMB)

Acids, Bases And Salts

View Answer

Question 21 Report

When chlorine is passed through a sample of water, the pH of the water sample would be

< 7

> 7

= 7

0

Answer Details

When chlorine gas is passed through water, it reacts with water to form hydrochloric acid (HCl) and hypochlorous acid (HClO). Hypochlorous acid is a weak acid and can dissociate to form hydrogen ions (H+) and hypochlorite ions (ClO-). The formation of H+ ions in the water will increase the concentration of H+ ions, resulting in a decrease in pH. Therefore, the pH of the water sample will be less than 7 (i.e., acidic) when chlorine is passed through it. It is important to note that the pH of the water sample will depend on the amount of chlorine passed through it, the initial pH of the water, and other factors such as temperature and the presence of other chemicals.

Read lesson note on Acids, Bases And Salts (JAMB)

Read lesson note on Acids, Bases And Salts (Ghana Only) (WAEC)

Acids, Bases And Salts

View Answer

Question 22 Report

The preferential discharge of ions during electrolysis is influenced by the

mechanism of electrolysis

electrolytic reactions

nature of the electrode

type of electrolytic cell

Answer Details

The preferential discharge of ions during electrolysis is influenced by the nature of the electrode and electrolytic reactions. During electrolysis, the positive and negative ions in the electrolyte solution move towards the respective electrodes. The electrode's surface and the type of electrolytic reaction determine the preferential discharge of ions. When an electrode's surface has a high affinity for a particular ion, that ion will preferentially discharge at that electrode. For example, if the electrode is made of copper and the electrolyte solution contains copper ions and hydrogen ions, copper ions will preferentially discharge at the electrode's surface. Additionally, the type of electrolytic reaction can influence ion preference. For instance, in the electrolysis of water, hydrogen ions are preferentially discharged at the cathode, and oxygen ions are preferentially discharged at the anode. The mechanism of electrolysis and type of electrolytic cell can also play a role in the preferential discharge of ions.

Read lesson note on Electrolysis (JAMB)

Electrolysis

View Answer

Question 23 Report

The position of equilibrium in a reversible reaction is affected by

particle size of the reactants

vigorous stirring of the reaction mixture

presence of a catalyst

change in concentration of the reactants

Answer Details

The position of equilibrium in a reversible reaction is affected by the change in concentration of the reactants. When the concentration of reactants changes, the rate of the forward and reverse reactions will also change, which will shift the position of the equilibrium to counteract the change in concentration. For example, if the concentration of reactants increases, the rate of the forward reaction will increase, which will shift the position of the equilibrium to the right to counteract the increase in concentration. Conversely, if the concentration of reactants decreases, the rate of the reverse reaction will increase, which will shift the position of the equilibrium to the left to counteract the decrease in concentration.

Read lesson note on Chemical Kinetics And Equilibrium Systems (Ghana Only) (WAEC)

Read lesson note on Chemical Equilibria (JAMB)

Chemical Kinetics And Equilibrium Systems (Ghana Only)

Chemical Equilibria

View Answer

Question 24 Report

What is the relative molecular mass of a compound which has empirical formula $CH_{2}O$? [C= 12, H= 1, O= 16]

42

45

126

180

Organic Compounds

View Answer

Question 25 Report

Consider the following equilibrium reaction: $2AB_{{2}{(g)}} + B_{{2}{(g)}} \to 2AB_{{3}{(g)}}$. $\Delta H= -X kJmol^{-1}$. The backward reaction will be favored by

a decrease in pressure

an increase in pressure

a decrease in temperature

an introduction of a positive catalyst

Chemical Equilibria

View Answer

Question 26 Report

What is the total number of shared pair of electrons in the compound above?

5

8

10

12

Structure Of The Atom

View Answer

Question 27 Report

Common Salt (NaCl) is used to preserve foods. Which of the following properties can be used to determine its purity before use?

Solubility in water

Melting point

Relative density

Crystalline nature

View Answer

Question 28 Report

Which of the following organic compounds can undergo both addition and substitution reactions?

Pentane

Benzene

Propane

Hexane

Answer Details

Benzene is the organic compound that can undergo both addition and substitution reactions. Benzene is an aromatic compound with a unique structure that includes a ring of six carbon atoms, each of which is bonded to a hydrogen atom. The electrons in the carbon-carbon double bonds are delocalized, making the molecule more stable and less reactive than typical alkenes. However, the delocalized electrons can still participate in reactions, including addition and substitution. Addition reactions involve the breaking of a double or triple bond and the addition of new atoms or groups of atoms. Because benzene already has delocalized double bonds, it can undergo addition reactions such as hydrogenation and halogenation, in which hydrogen or a halogen is added to the ring. Substitution reactions involve the replacement of one atom or group of atoms with another atom or group of atoms. Benzene is particularly prone to substitution reactions because the delocalized electrons in the ring make it more susceptible to attacks by electrophiles, which are electron-deficient species that can accept a pair of electrons. Substitution reactions include nitration, sulfonation, and halogenation.

View Answer

Question 29 Report

Analysis of a hydrocarbon shows that it contains 0.93g of Carbon per gram of the compound. The mole ratio of carbon to hydrogen in the compound is [H = 1.0, C=12.0]

1:1

1:2

2:1

2:3

Answer Details

The ratio of carbon to hydrogen in the hydrocarbon can be determined using the given mass ratio of carbon and the fact that the molecular weight of the hydrocarbon is the sum of the atomic weights of its constituent elements. Let's assume a sample of 1 gram of the hydrocarbon, which contains 0.93 grams of carbon. This means that the mass of hydrogen in the sample is 1.0 - 0.93 = 0.07 grams. The number of moles of carbon in the sample can be calculated as: 0.93 g C x (1 mol C / 12.0 g C) = 0.0775 mol C Similarly, the number of moles of hydrogen in the sample can be calculated as: 0.07 g H x (1 mol H / 1.0 g H) = 0.07 mol H To find the mole ratio of carbon to hydrogen, we need to divide the number of moles of carbon by the number of moles of hydrogen: 0.0775 mol C / 0.07 mol H = 1.107 Rounding this to the nearest whole number, we get the mole ratio of carbon to hydrogen as 1:1. Therefore, the correct answer is 1:1.

Read lesson note on Stoichiometry And Chemical Reactions (WAEC)

Stoichiometry And Chemical Reactions

View Answer

Question 30 Report

The law of definite proportions states that

pure samples of the same compound contain the same elements combined in the same proportion by mass

pure samples of substances are in the same proportion by mass

chemical compounds are pure because they contain the same elements

matter can neither be created nor destroyed.

Answer Details

The law of definite proportions states that pure samples of the same compound contain the same elements combined in the same proportion by mass. This means that no matter where or how the compound is obtained, the ratio of the masses of the elements in the compound will always be the same. For example, if a water molecule contains 2 hydrogen atoms and 1 oxygen atom, the ratio of the masses of hydrogen to oxygen will always be 2:1 in any sample of water.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

View Answer

Question 31 Report

When zinc is added to AgNO$_{3}$ solution, crystals of silver forms on the zinc surface. This indicates that zinc is

oxidised

reduced

decomposed

dissociated

Oxidation And Reduction

View Answer

Question 32 Report

$Cu$ and $HNO_{3}$ are not suitable for preparing hydrogen gas because of their

reactivity and oxidation respectively

conductivity and corrosiveness respectively

melting point and reduction respectively

electronegativity and solubility respectively

Answer Details

Copper ($Cu$) and nitric acid ($HNO_{3}$) are not suitable for preparing hydrogen gas because of their reactivity and oxidation properties, respectively. When copper is placed in nitric acid, a redox reaction occurs, where the copper is oxidized by the nitric acid. This reaction produces copper nitrate and nitrogen dioxide gas, but it does not produce hydrogen gas. Similarly, nitric acid is a strong oxidizing agent and can oxidize hydrogen gas to water, thereby preventing the formation of hydrogen gas. Therefore, neither copper nor nitric acid can be used to prepare hydrogen gas. Other metals, such as zinc or magnesium, can be used to react with acids to produce hydrogen gas because they are more reactive than copper and do not have the same oxidation properties as nitric acid.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

Read lesson note on Acids, Bases And Salts (JAMB)

Acids, Bases And Salts

View Answer

Question 33 Report

Pure water can be made to boil at a temperature lower than 100°C by

reducing its quantity

decreasing the external pressure

distilling it

increasing the external pressure

View Answer

Question 34 Report

The valence electrons of $_{12}Mg$ are in the

3s orbital

2p$_{x}$

2s orbital

1s orbital

Answer Details

The valence electrons of magnesium, which has an atomic number of 12, are located in the 3s orbital. In an atom, electrons are arranged in shells surrounding the nucleus. The innermost shell, the 1s orbital, holds the electrons closest to the nucleus and is usually filled first. The next shell, the 2s orbital, is further away from the nucleus and is also filled before the third shell, the 3s orbital. In the case of magnesium, it has 12 electrons, and so the first two shells are completely filled. The 3rd shell, which is the valence shell, has only two electrons in the 3s orbital. These are the valence electrons, and they are the electrons that are involved in chemical reactions and bonding with other atoms.

Read lesson note on Atomic Structure And Bonding (JAMB)

View Answer

Question 35 Report

At what temperature does the solubility of $KNO_{3}$ equal that of $NaNO_{3}$?

0°C

20°C

30°C

40°C

Solubility Of Substances (Ghana Only)

Solutions

View Answer

Question 36 Report

Consider the following reaction equation: $2HCl + Ca(OH)_{2} \to CaCl_{2} + H_{2}O$. What is the volume of 0.1$moldm^{-3}$ HCl that would completely neutralize 25$cm^{3}$ of 0.3$moldm^{-3}$ Ca(OH)$_{2}$?

150$cm^{3}$

75$cm^{3}$

30$cm^{3}$

25$cm^{3}$

Stoichiometry And Chemical Reactions

View Answer

Question 37 Report

The change in the oxidation state of iron in the reaction represented by the equation: $2FeCl_{3} + H_{2}S \to 2FeCl_{2} + 2HCl + S$ is

+2 to +3

0 to +2

+3 to +2

+3 to 0

Answer Details

In the given chemical equation, the reactants are iron(III) chloride ($FeCl_{3}$) and hydrogen sulfide ($H_{2}S$), and the products are iron(II) chloride ($FeCl_{2}$), hydrogen chloride ($HCl$), and sulfur ($S$). Let's consider the oxidation state of iron in the reactants and products. Iron has a variable oxidation state, and it can exist in either +2 or +3 oxidation state in its compounds. In $FeCl_{3}$, iron has an oxidation state of +3. Hydrogen sulfide ($H_{2}S$) has sulfur in -2 oxidation state. In the product $FeCl_{2}$, iron has an oxidation state of +2. Sulfur in the product is in 0 oxidation state. Therefore, in the given chemical equation, the oxidation state of iron changes from +3 in the reactant ($FeCl_{3}$) to +2 in the product ($FeCl_{2}$). Hence the correct answer is "+3 to +2".

Read lesson note on Oxidation And Reduction (JAMB)

Oxidation And Reduction

View Answer

Question 38 Report

The most suitable substance for putting out petrol fire is

water

carbon(IV) oxide

fire blanket

sand

Answer Details

The most suitable substance for putting out a petrol fire is not water, carbon(IV) oxide, or a fire blanket, but sand. Sand can be used to smother a petrol fire by covering the flames and cutting off the oxygen supply, which will cause the fire to go out. However, it is important to note that sand should only be used on small fires and not on larger fires, as it can be difficult to spread a large amount of sand over the fire and it may not be effective. In such cases, it is best to evacuate the area and call the fire department.

Read lesson note on Water (JAMB)

Read lesson note on Solutions (WAEC)

Water

Solutions

View Answer

Question 39 Report

The process of extraction of iron from its ore is

decomposition

oxidation

reduction

sublimation

Answer Details

The process of extracting iron from its ore involves the reduction of the iron oxide (Fe2O3) in the ore to iron metal. This is achieved through a chemical reaction between the iron oxide and carbon (in the form of coke) in a blast furnace. First, the iron ore is crushed and mixed with coke and limestone. The coke, which is mostly carbon, serves as a reducing agent by combining with the oxygen in the iron oxide to form carbon dioxide (CO2). This reaction produces heat and carbon monoxide (CO). The carbon monoxide then reacts with the iron oxide to produce iron metal and more carbon dioxide. The limestone is added to the furnace to remove impurities such as silica (SiO2) that would otherwise interfere with the chemical reaction. The molten iron is then tapped off from the bottom of the furnace and can be further processed into steel.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

Read lesson note on Redox Reactions (WAEC)

Redox Reactions

View Answer

Question 40 Report

Which of the following statements best explains the difference between a gas and a vapour?

Unlike gases, vapours are liquids at room temperature

Unlike gases, vapour can easily be condensed into liquids

Unlike gases, vapour is readily converted into solids

Vapours are generally denser than gases

Answer Details

The best explanation for the difference between a gas and a vapor is: Unlike gases, vapors can easily be condensed into liquids. Gases and vapors are both in the gaseous state of matter, which means they have no fixed shape or volume and can expand to fill any container. However, vapors are substances that are normally in the liquid or solid state at room temperature and pressure, but are volatilized (turned into a gas) through evaporation or boiling. The main difference between gases and vapors is that gases are typically elements or compounds that are naturally in the gaseous state, whereas vapors are substances that have been volatilized from their liquid or solid state. Since vapors have been volatilized from their liquid or solid state, they can easily be condensed back into a liquid or solid form by cooling or compressing them. Therefore, the correct statement that explains the difference between a gas and a vapor is that "unlike gases, vapors can easily be condensed into liquids." The other options given are not true or do not accurately explain the difference between gases and vapors.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

View Answer

Question 41 Report

Ethene is produced from ethanol by

decomposition

hydrolysis

ozonolysis

dehydration

Answer Details

Ethene is produced from ethanol by: Dehydration. Dehydration is the process of removing water from a compound. In the case of ethanol, the process of dehydration involves removing a molecule of water (H2O) from two molecules of ethanol (C2H5OH) to form one molecule of ethene (C2H4). The reaction is typically carried out using a catalyst, such as concentrated sulfuric acid or aluminum oxide. The chemical equation for the reaction of ethanol to produce ethene by dehydration is: C2H5OH → C2H4 + H2O Therefore, the correct answer is "dehydration" - ethanol is converted to ethene by removing a molecule of water through the process of dehydration. The other options - decomposition, hydrolysis, and ozonolysis - do not accurately describe the process of producing ethene from ethanol.

Read lesson note on Chemical Kinetics And Equilibrium System (Nigeria Only) (WAEC)

Chemical Kinetics And Equilibrium System (Nigeria Only)

View Answer

Question 42 Report

The following factors would contribute to environmental pollution except

production of ammonia

manufacture of cement

photosynthesis

combustion

Answer Details

Environmental pollution can be caused by a variety of factors, including the release of harmful chemicals and substances into the air, water, or soil. Of the options provided, photosynthesis is the factor that would not contribute to environmental pollution. Photosynthesis is the process by which plants use sunlight to convert carbon dioxide and water into oxygen and glucose. This natural process does not release any harmful chemicals or substances into the environment and, in fact, helps to improve air quality by producing oxygen. On the other hand, the production of ammonia, manufacture of cement, and combustion are all activities that can release harmful pollutants into the environment. Ammonia production can release nitrogen oxide and other harmful chemicals into the air and water, while cement manufacturing can release large amounts of carbon dioxide into the atmosphere. Combustion, whether in vehicles or power plants, can release harmful gases and particulate matter into the air. Therefore, photosynthesis is the only option among the given factors that would not contribute to environmental pollution.

Read lesson note on Environmental Pollution (JAMB)

Environmental Pollution

View Answer

Question 43 Report

What is the mass of solute in 500$cm^{3}$ of 0.005$moldm^{-3}$ $H_{2}SO_{4}$? ( H = 1, S = 32.0, O=16.0)

0.490g

0.049g

0.245g

0.0245g

Answer Details

n = cv where n = no of mole, c = molar concentration(mol/dm3) and v = volume( dm3)

volume = 500

$c m^{3}$ $c m^{3}$ $c m^{3}$
$c m^{3}$ $c m^{3}$ $c m^{3}$ $c m^{3}$ $c m^{3}$ = 0.5dm3, c = 0.005 $m o l d m^{- 3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$
$m o l d m^{- 3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$
$\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ = 0.0025 = $\frac{m a s s}{98}$ $\frac{m a s s}{98}$ $\frac{m a s s}{98}$
$\frac{m a s s}{98}$ $\frac{m a s s}{98}$ $\frac{m a s s}{98}$ $\frac{m a s s}{98}$ $\frac{m a s s}{98}$ $\frac{m a s s}{98}$ $\frac{m a s s}{98}$ $\frac{m a s s}{98}$ (where 98g/mol is the molar mass of H2SO4)

$c m^{3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$ $m o l d m^{- 3}$

number of mole(n) = c x v = 0.5 X 0.005 = 0.0025mol.

but n = $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{m o l a r m a s s}$ $\frac{m a s s}{98}$ $\frac{m a s s}{98}$ $\frac{m a s s}{98}$

mass of H2SO4 = 0.0025 x 98 = 0.245g.

Read lesson note on Solubility Of Substances (Ghana Only) (WAEC)

Read lesson note on Acids, Bases And Salts (Ghana Only) (WAEC)

Solubility Of Substances (Ghana Only)

View Answer

Question 44 Report

Which of the following properties would not influence electrovalent bond formation?

Electronegativity

Electron Affinity

Ionization potential

Catalytic ability

Answer Details

The property that would not influence electrovalent bond formation is catalytic ability. An electrovalent bond, also known as an ionic bond, is formed when atoms transfer electrons from one to another, resulting in the formation of ions with opposite charges. This bond is typically formed between atoms with significantly different electronegativities. The electronegativity of an atom is a measure of its ability to attract electrons towards itself, and it is a key factor in determining the type of bond that will form between two atoms. Electron affinity is the energy change that occurs when an electron is added to a neutral atom to form a negative ion. This property also influences the formation of electrovalent bonds. Ionization potential is the energy required to remove an electron from an atom. This property can also affect the formation of electrovalent bonds, as it can influence the ability of an atom to give up electrons. Catalytic ability, on the other hand, is the ability of a substance to speed up a chemical reaction without being consumed in the reaction. This property has no direct influence on the formation of electrovalent bonds. To summarize, the property that would not influence electrovalent bond formation is catalytic ability, while electronegativity, electron affinity, and ionization potential all have an impact on the formation of these types of bonds.

Read lesson note on Atomic Structure And Bonding (JAMB)

View Answer

Question 45 Report

The bonding pair of electrons in a Hydrogen Chloride molecule is pulled towards the chlorine atom because

chlorine has a larger atomic size

chlorine has a larger atomic mass

chlorine is more electronegative

there is no bonding orbitals within the hydrogen atom

Answer Details

The correct answer is that chlorine is more electronegative than hydrogen. Electronegativity is a measure of an atom's ability to attract electrons towards itself in a covalent bond. Chlorine has a higher electronegativity than hydrogen, which means that the bonding pair of electrons in a hydrogen chloride molecule is pulled more towards the chlorine atom than towards the hydrogen atom. This creates a partial positive charge on the hydrogen atom and a partial negative charge on the chlorine atom, forming a polar molecule.

Read lesson note on Atomic Structure And Bonding (JAMB)

View Answer

Question 46 Report

One of the criteria for confirming the purity of benzene is to determine its

heat capacity

boiling point

mass

colour

Answer Details

One of the criteria for confirming the purity of benzene is to determine its boiling point. The boiling point of a substance is a physical property that is determined by the intermolecular forces between the particles in the substance. These forces are dependent on the molecular structure of the substance, and so the boiling point is unique for each substance. In the case of benzene, it has a known and well-defined boiling point of 80.1 °C. By determining the boiling point of a sample and comparing it to the known boiling point of pure benzene, we can determine the purity of the sample. If the boiling point of the sample is different from the known boiling point of pure benzene, it indicates that the sample is impure and contains other substances. So, determining the boiling point of a sample of benzene is a useful way to confirm its purity.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

Read lesson note on Acids, Bases And Salts (Ghana Only) (WAEC)

View Answer

Question 47 Report

Consider the following reaction equation: $Br_{2} + 2KI \to 2KBr + I_{2}$. Bromine is acting as

an oxidizing agent

a reducing agent

an acid

a base

Answer Details

In the given reaction, the bromine molecule (Br2) is reacting with two potassium iodide molecules (2KI) to form two potassium bromide molecules (2KBr) and one iodine molecule (I2). During this reaction, the bromine molecule is gaining electrons (receiving electrons) and being reduced, while the iodine molecule is losing electrons (donating electrons) and being oxidized. Therefore, we can conclude that the bromine molecule is acting as a oxidizing agent because it is causing the oxidation of the iodine molecule by accepting electrons, and therefore, itself being reduced.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

Read lesson note on Oxidation And Reduction (JAMB)

Oxidation And Reduction

View Answer

Question 48 Report

Which of the following electron configurations represents the transition element Chromium $_{24}Cr$?

$1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{2} 3d^{4}$

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{6}$

$1s^{2}2s^{2}2p^{6}3s^{2}3d^{4} 4s^{1}$

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{5}$

Answer Details

The electron configuration for Chromium $_{24}Cr$ is $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{1} 3d^{5}$. Electron configuration is a description of the arrangement of electrons in an atom. It is represented by a series of numbers and letters that indicate the energy level, or shell, and the orbital, or subshell, that each electron resides in. In the case of Chromium, the electron configuration starts with the first energy level, which is filled with two electrons in the 1s orbital. The second energy level has two electrons in the 2s orbital and six electrons in the 2p orbital. The third energy level has two electrons in the 3s orbital and six electrons in the 3p orbital. Finally, the fourth energy level has one electron in the 4s orbital and five electrons in the 3d orbital. So, out of the given options, the electron configuration that represents Chromium $_{24}Cr$ is $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{1} 3d^{5}$.

Read lesson note on Atomic Structure And Bonding (JAMB)

View Answer

Question 49 Report

The empirical formula of a compound containing 0.067mol Cu and 0.066mol O is [Cu = 63.5, O = 16]

$Cu_{2}O$

$CuO$

$CuO_{2}$

$CuO_{4}$

Answer Details

To determine the empirical formula of the compound, we need to find the simplest whole number ratio of the atoms present in the compound. Given that the compound contains 0.067 mol Cu and 0.066 mol O, we need to first convert the moles to whole numbers. Dividing both values by the smaller value (0.066 mol), we get: Cu: 0.067 mol ÷ 0.066 mol ≈ 1.02 ≈ 1 O: 0.066 mol ÷ 0.066 mol = 1 So, the ratio of Cu to O atoms is 1:1. Therefore, the empirical formula of the compound is CuO. We can check that the formula is correct by calculating the molar mass of CuO and comparing it to the experimental data. Molar mass of CuO = 63.5 g/mol + 16 g/mol = 79.5 g/mol The experimental data gives us: (0.067 mol)(63.5 g/mol) + (0.066 mol)(16 g/mol) = 4.2495 g The molar mass calculated from the experimental data is: (4.2495 g) / (0.133 mol) ≈ 31.97 g/mol This is close to the molar mass of CuO (79.5 g/mol), which confirms that the empirical formula is CuO.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

View Answer

Question 50 Report

Atoms are electrically neutral because they

do not conduct electricity

contain equal number of protons and electrons

are composed of neutrons and electrons

cannot be attracted by electromagnetic field.

Answer Details

The correct answer is that atoms are electrically neutral because they contain an equal number of protons and electrons. Protons have a positive charge, while electrons have a negative charge. In an atom, the number of protons in the nucleus is equal to the number of electrons orbiting around the nucleus. The positive charge of the protons is balanced by the negative charge of the electrons, resulting in an overall charge of zero for the atom. This balance of positive and negative charges is what makes atoms electrically neutral.

Read lesson note on Atomic Structure And Bonding (JAMB)