WAEC SSCE - Chemistry - 1996 (Objective)

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Question 2 Report

If the third member of a homologous series is C₃H₈, the fifth member will be

C ₅H₈

C₅H₉

C₅H₁₀

C₅H₁₁

C₅H₁₂

Answer Details

A homologous series is a series of organic compounds having the same functional group and similar chemical properties in which the successive members differ by a CH₂ unit. So, the general formula of the homologous series would be C_nH_2n+2. If the third member of a homologous series is C₃H₈, it means that the general formula of the series is C_nH_2n+2, where n = 3. C₃H₈ belongs to the alkane series, so the fifth member of the series would also belong to the alkane series and have the general formula C_nH_2n+2, where n = 5. Substituting n = 5 in the general formula, we get C₅H₂₍₅₎₊₂ = C₅H₁₂. Therefore, the fifth member of the homologous series would be C₅H₁₂.

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Question 3 Report

The existance of two or more forms of the same element in the same physical state is known as

allotropy

resonance

hybridization

isotopy

isomerism

Answer Details

The existence of two or more forms of the same element in the same physical state is known as allotropy. Allotropy is the property of some elements to exist in two or more different forms, called allotropes. These allotropes have different physical and chemical properties due to the different arrangements of atoms in their crystal lattice structures. For example, carbon has three common allotropes: diamond, graphite, and fullerene. Each of these allotropes has different physical and chemical properties despite being made up of the same element.

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Chemical Combination

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Question 4 Report

The cleansing action of soap in hard water is not satisfactory because soap

forms insoluble calcium and magnesium salts

is made from fats and oils

has an organic component

alters the surface tension of water

is a sodium salt of higher carboxylic acids

Answer Details

Soap is made up of sodium or potassium salts of long-chain fatty acids. The cleaning action of soap is due to its ability to dissolve in water and attach to oil and dirt particles, enabling them to be washed away. However, in hard water, which contains dissolved calcium and magnesium ions, soap forms insoluble salts with these ions. These salts, called scum, are insoluble in water and stick to surfaces, reducing the effectiveness of the soap. As a result, the cleansing action of soap in hard water is not satisfactory.

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Question 5 Report

The rate of production of hydrogen gas from the reaction between zinc granules and hydrochloric acid can be increased by

cooling the reaction mixture

using zinc powder instead of zinc granules

using zinc rod instead of zinc granules

carrying out the reaction at a higher pressure

carrying out the reaction in a closed vessel

Answer Details

The rate of production of hydrogen gas from the reaction between zinc granules and hydrochloric acid can be increased by using zinc powder instead of zinc granules. The rate of reaction between zinc and hydrochloric acid is determined by the surface area of the zinc that is exposed to the acid. Zinc powder has a higher surface area than zinc granules, which increases the rate of reaction between the zinc and the acid. Cooling the reaction mixture would slow down the reaction rate because the reaction is exothermic and releasing energy as heat, and lowering the temperature would reduce the kinetic energy of the reacting particles. Using a zinc rod instead of zinc granules would not increase the surface area, but would decrease it, slowing down the reaction rate. Carrying out the reaction at a higher pressure or in a closed vessel would not increase the surface area of the zinc and would not affect the rate of reaction.

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Rates Of Chemical Reaction

Chemical Kinetics And Equilibrium Systems (Ghana Only)

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Question 6 Report

What is the likely formula of compound formed between element M in group two and element X in group seven?

M₇X₂

M₂X

M₂X₇

MX₂

MX₆

Answer Details

When elements in group two (alkaline earth metals) react with elements in group seven (halogens), they form ionic compounds with a general formula of MX₂. Therefore, the likely formula of the compound formed between element M in group two and element X in group seven is MX₂.

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Chemical Combination

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Question 7 Report

When acidified KMnO₄ solution is decolorised by ethene, the gas acts as

a straight-chain hydrocarbon

a saturated hydrocarbon

a reducing agent

a dehydrating agent

an oxidizing agent

Answer Details

When acidified KMnO₄ solution is decolorised by ethene, it means that ethene is oxidised to a colorless compound and KMnO₄ is reduced. Therefore, ethene is acting as a reducing agent. So, the correct option is (c) a reducing agent.

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Question 8 Report

Ammonia gas is suitable for performing the 'Fountain' experiment because the gas is

colourless

a cooling agent

alkaline to litmus

a reducing agent

very soluble in water

Answer Details

Ammonia gas is suitable for performing the 'Fountain' experiment because it is very soluble in water. In the experiment, ammonia gas is passed through water, where it dissolves to form an alkaline solution. The gas bubbles produced rise to the top of the solution, and as more gas bubbles are produced, the solution becomes saturated with the gas. Eventually, the pressure of the gas forces the solution to rise up and out of the container, creating a fountain-like effect. Ammonia gas is preferred for this experiment because of its high solubility in water, which allows for a sufficient amount of gas to dissolve in the solution and produce the necessary pressure for the fountain effect.

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Question 9 Report

Use this following information to answer this question. Compound X was boiled with concentrated hydrochloric acid for a long time. One of the products was found to be a sugar. What type of reaction was involved between compound X and concentrated hydrochloric acid?

Polymerization

Fermentation

Hydrolysis

Neutralization

Esterification

Answer Details

The reaction between compound X and concentrated hydrochloric acid involves hydrolysis. Hydrolysis is a type of chemical reaction in which a compound is broken down into two or more simpler compounds through the addition of water. In this case, the concentrated hydrochloric acid acts as a catalyst, promoting the breakdown of compound X into simpler compounds, one of which is a sugar. Therefore, the reaction between compound X and concentrated hydrochloric acid is a hydrolysis reaction.

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

Kinetic Theory Of Matter And Gas Laws

Acids, Bases And Salts

Separation Of Mixtures And Purification Of Chemical Substances

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Question 10 Report

The component of air that can be removed by alkaline pyrogallol solution is

oxygen

nitrogen

water vapour

carbon (IV) oxide

noble gases

Answer Details

Alkaline pyrogallol solution is commonly used to remove oxygen from a gas mixture. This is because pyrogallol can easily react with oxygen in the air to form a brown precipitate. Therefore, the component of air that can be removed by alkaline pyrogallol solution is oxygen.

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Air

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Question 11 Report

In which of the following compounds is the oxidation number of nitrogen equal to + 3?

NO ₂

N ₂O

NO

HNO₂

HNO₃

Answer Details

The oxidation number of an element is the hypothetical charge it would have if all its bonds were purely ionic. In other words, it is a measure of the degree of oxidation of an atom in a molecule. To determine the oxidation number of nitrogen in each compound, we need to know the electronegativity of the other elements involved in the bond. In NO₂, the electronegativity of oxygen is higher than nitrogen, so nitrogen is assigned an oxidation number of +4. In N₂O, the oxidation number of nitrogen is +1. In NO, nitrogen is assigned an oxidation number of +2. In HNO₂, nitrogen is assigned an oxidation number of +3. In HNO₃, nitrogen is assigned an oxidation number of +5. Therefore, the only compound in which the oxidation number of nitrogen is equal to +3 is HNO₂.

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Oxidation And Reduction

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Question 12 Report

When excess carbon (lV) oxide is passed into lime water, the turbidity produced initially disappears due to the formation of

calcium oxide

calcium carbide

calcium hydrogentrioxocarbonate (IV)

trioxocarbonate (IV) acid

calcium trioxocarbonate (IV)

Chemistry Of Carbon Compounds (Nigeria Only)

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Question 13 Report

What amount of copper is deposited when 13.0g of zinc reacts with excess copper (ll) tetraoxosulphate (IV) solution according to the following equation? Zn _(s) + CuSO_4(aq) → ZnSO_4(aq) + Cu _(s) [Cu =63,5, Zn = 65]

0.1 mole

0.2mole

0.3 mole

0.4 mole

0.5 mole

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Question 14 Report

The following are properties of transition metals except

variable oxidation states

tendency to form complext ions

formation of coloured ions

ability to act as catalyst

low melting points

Answer Details

The incorrect statement about transition metals is "low melting points". Transition metals are characterized by a high melting and boiling point due to their strong metallic bonding, which involves the delocalization of electrons over a large number of atoms. Other properties of transition metals include variable oxidation states, tendency to form complex ions, formation of coloured ions, and ability to act as catalysts.

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Chemical Bonds (Nigeria Only)

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Question 15 Report

Which of the following is not correct about a catalyst? It

remains unchanged chemically at the end of a reaction

helps to establish equilibrium faster reversible reaction

can start a chemical rection which will normally not take place

is usually specific in its action

alters the rate of chemical reaction

Answer Details

The statement that is not correct about a catalyst is: "can start a chemical reaction which will normally not take place." A catalyst cannot start a chemical reaction that will normally not take place because a catalyst only speeds up the rate of an existing reaction. It works by lowering the activation energy required for a reaction to occur, thus making it easier for the reaction to take place. Once the reaction is completed, the catalyst remains unchanged and can be used again. Therefore, options a, b, d, and e are all correct statements about a catalyst, while the statement in option c is not correct.

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

Chemical Kinetics And Equilibrium System (Nigeria Only)

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Question 16 Report

The alkali metals exhibit similar chemical properties because

they occur in the combined state

they have the same number of vallence electrons

they form crystalline salts

their salts are soluble in water

they are highly reactive

Answer Details

The alkali metals are a group of elements in the periodic table that include lithium, sodium, potassium, rubidium, cesium, and francium. They exhibit similar chemical properties because they all have one valence electron in their outermost shell, which they readily give up to form positive ions. This makes them highly reactive and they are easily oxidized in air or water. The similarity in their electronic configuration results in similar chemical behavior, such as the ability to form ionic compounds with non-metals and the tendency to react vigorously with water to produce hydrogen gas and an alkali metal hydroxide.

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Non-metals And Their Compounds

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Question 17 Report

On exposing palm wine to air for some days, it becomes sour owing to the conversion of

glucose to ethanol

glucose to gluconic acid

ethanol to ethanoic acid

ethanol to ethanal

palm wine to palmitic acid

Answer Details

Palm wine is a fermented beverage that is produced from the sap of certain palm trees. The fermentation process is mainly carried out by yeast, which converts glucose to ethanol. When palm wine is exposed to air, the ethanol undergoes oxidation, which results in the formation of ethanoic acid. This is what causes the sour taste of the palm wine. Therefore, the correct answer is "ethanol to ethanoic acid."

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Oxidation And Reduction

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Question 18 Report

The products formed when sodium hydrogen trioxocarbonate (IV) is heated strongly are

carbon (IV) oxide and sodium hydride

carbon (IV) oxide and soudium trioxocarbonate (IV)

sodium trioxocarbonate (IV) and steam

carbon (IV) oxide and steam

sodium trioxocarbonate (IV) carbon (IV) oxide and steam

Acids, Bases And Salts

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Question 19 Report

Which of the following is a disaccharide?

fructose

starch

cellulose

sucrose

glycogen

Answer Details

Sucrose is a disaccharide. A disaccharide is a type of carbohydrate made up of two monosaccharides linked together by a glycosidic bond. Sucrose, also known as table sugar, is composed of glucose and fructose joined together by a glycosidic bond. The other options listed are not disaccharides; fructose is a monosaccharide, starch, cellulose, and glycogen are polysaccharides.

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SOLUBILITY OF SUBSTANCES (Nigeria Only)

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Question 20 Report

During water treatment for town supply, water is passed through layers of send beds in order to

soften the water

filter the water

decolorize the water

destroy the germs in the water

coagulate colloidal particles in the water

Answer Details

During water treatment for town supply, water is passed through layers of sand beds in order to filter the water. The sand beds act as a physical barrier that separates large particles, sediments, and debris from the water. As the water flows through the sand bed, the sand traps the suspended particles, and clean water passes through. This process is called filtration and is an essential step in water treatment, as it removes impurities and improves the quality of the water. The filtered water can then be treated further to remove any remaining impurities or disinfect it to kill any harmful bacteria and viruses.

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Water

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Question 21 Report

When an atom gains an electron, it becomes properties

chemically inactive

negatively charged

oxidized

a cation

a complex ion

Answer Details

When an atom gains an electron, it becomes negatively charged because it now has more electrons than protons. This negatively charged atom is called an anion. The extra electron is held by the nucleus through the electromagnetic force and affects the chemical properties of the atom. The anion has a greater affinity for positively charged ions or cations and can undergo chemical reactions, forming compounds with other atoms or ions. Therefore, the correct option is "negatively charged."

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Question 22 Report

What volume of carbon (lV) oxide is produced at s.t.p. when 2.5g of CaCO₃ reacts with excess acid according to the following equation? CaCO₃ + 2HCI → CaCI2 +H₂O + CO₂ [CaCO₃ = 100; molar volume of a gas at s.t.p = 22.4dm³]

11.20dm³

5.60dm³

2.24dm³

0.56dm³

0.28dm³

Answer Details

The balanced equation for the reaction between CaCO₃ and 2HCI is: CaCO₃ + 2HCI → CaCI₂ + H₂O + CO₂ The molar mass of CaCO₃ is 100 g/mol, which means that 100 g of CaCO₃ will produce 1 mole of CO₂. Therefore, 2.5 g of CaCO₃ will produce: 1 mole CO₂ = 22.4 dm³ at s.t.p. x moles CO₂ = (2.5 g / 100 g/mol) = 0.025 moles x = 0.56 dm³ (rounded to two decimal places) Therefore, the volume of CO₂ produced at s.t.p is 0.56 dm³. Hence, the answer is (d) 0.56 dm³.

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Question 23 Report

Which of the following statements is not correct about electrolysis?

Reduction occurs at the anode

Anions migrate to the anode

Positive ions migrate to the cathode

Concentration affects the discharge of ions

Electrolytes conduct electric current

Answer Details

The statement that is not correct about electrolysis is "Reduction occurs at the anode". During electrolysis, reduction occurs at the cathode and oxidation occurs at the anode. At the anode, positively charged ions (cations) lose electrons to become neutral atoms or molecules. At the cathode, negatively charged ions (anions) gain electrons to become neutral atoms or molecules. Anions migrate to the anode, while positive ions migrate to the cathode. The concentration of the electrolyte affects the rate of the reaction and the discharge of ions. Electrolytes conduct electric current because they contain ions that are free to move and carry charge.

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Electrolysis

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Question 24 Report

What is the role of MnO₂ in the reaction represented by the following equation?MnO₂ + 4HCI₂ + CI₂ + 2H₂O

Bleaching agent

Oxidizing agent

Amphoteric oxide

Basic oxide

Catalyst

Oxidation And Reduction

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Question 25 Report

What does X represent in the following equation? H _2(g) + 1/2O_2(g) → H₂O _(l); ∆H = xKJ.

Bond energy

Activation energy

Ionization energy

Enthalpy of neutralization

Enthalpy of formation

Answer Details

In the given chemical equation, X represents the Enthalpy of Formation. Enthalpy of formation (∆H_f) is defined as the amount of heat energy released or absorbed when one mole of a compound is formed from its constituent elements in their standard states under standard conditions. In the given equation, the reactants are hydrogen gas and oxygen gas in their standard states, and the product is liquid water. The value of ∆H represents the amount of heat energy that is either released or absorbed when one mole of water is formed from its constituent elements. If the value of ∆H is negative, it means that the reaction is exothermic, i.e., heat energy is released during the reaction, while a positive value of ∆H represents an endothermic reaction, i.e., heat energy is absorbed during the reaction.

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Rates Of Chemical Reaction

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Question 26 Report

Which of the following exhibits resonance?

Benzene

Butane

Pentene

Octana

Hexene

Answer Details

Benzene exhibits resonance. Resonance is a phenomenon in which electrons move between different possible locations within a molecule, resulting in the stabilization of the molecule. In benzene, the carbon atoms are arranged in a ring with alternating double bonds and single bonds. The electrons in the double bonds are delocalized and move freely around the ring, resulting in a more stable molecule. This is an example of resonance. The other molecules listed do not have a similar arrangement and therefore do not exhibit resonance.

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Chemical Bonds (Ghana Only)

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Question 27 Report

Amphoteric oxides are oxides which

react with water to form acids

react with water to form alkali

show neither acid nor basic properties

react with acids alkalis

contain high proportion of oxygen

Acids, Bases And Salts

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Question 28 Report

The following salts will produce a gas on reacting with hydrochloric acid except

CuSO₄

CaCO₃

FeS

Na₂SO₃

K₂CO₃

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Question 29 Report

A solution of pH 7 is

acidic

neutral

concentrated

dilute

saturated

Answer Details

A solution of pH 7 is neutral. The pH scale ranges from 0 to 14, with pH 7 being the midpoint of the scale. A pH of 7 indicates a balance of hydrogen ions (H+) and hydroxide ions (OH-) in the solution, with equal concentrations of both ions. In other words, a neutral solution is neither acidic nor basic.

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Acids, Bases And Salts

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Question 30 Report

An arrangement of two different metals in aqueous solutions of their salts to produce an electronic current is known as

electrochemical cell

activity series

thermocouple

voltameter

galvanometer

Answer Details

An arrangement of two different metals in aqueous solutions of their salts to produce an electronic current is known as an electrochemical cell. This is because the cell involves a chemical reaction that converts chemical energy into electrical energy. One of the metals acts as a negative electrode and the other as a positive electrode, and the movement of electrons between them through the salt bridge or porous membrane generates an electric current. This process is used in batteries and other electronic devices to produce electrical energy.

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Electrolysis

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Question 31 Report

Use this following information to answer this question. Compound X was boiled with concentrated hydrochloric acid for a long time. One of the products was found to be a sugar. Compound X was probably

rubber

polyethene

nylon

cellulose

ethanol

Answer Details

The fact that a sugar was produced by boiling Compound X with concentrated hydrochloric acid suggests that Compound X was likely a carbohydrate, specifically a type of polysaccharide such as cellulose. When polysaccharides undergo hydrolysis (a reaction with water), they are broken down into their constituent monosaccharides (simple sugars) by the addition of water molecules. Therefore, the production of a sugar as a product of the reaction between Compound X and hydrochloric acid suggests that the reaction involved hydrolysis of the polysaccharide. The other compounds listed (rubber, polyethylene, nylon, and ethanol) are not polysaccharides and would not be expected to produce a sugar upon hydrolysis.

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

Chemistry Of Carbon Compounds (Nigeria Only)

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Question 32 Report

Which of the following metals will be the most suitable for use where lightness and resistance to corrosion are of importance?

Lead

Copper

Iron

Calcium

Aluminium

Answer Details

The most suitable metal for use where lightness and resistance to corrosion are of importance is Aluminium. This is because Aluminium is a lightweight metal that has a low density and is resistant to corrosion. Aluminium forms a protective layer of oxide on its surface that prevents further oxidation, making it highly resistant to corrosion. In addition, Aluminium is a good conductor of heat and electricity and can be easily shaped into different forms, making it useful for a wide range of applications, such as in the aerospace and automotive industries, where weight reduction and corrosion resistance are critical factors. Therefore, the correct answer is Aluminium.

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Metals And Their Compounds

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Question 33 Report

What amount of hydrogen will be required for complete hydrogenation of one mole of pent-3-yne?

1 mole

2 moles

3 moles

5 moles

6 moles

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Question 34 Report

''Equal volumes of all gases at the same temperature and pressure contain the same number of molecules'' is an expression of

Charles Law

Boyle's Law

Avogadro's Law

Graham's Law

Gay Lussac's Law

Answer Details

The statement ''Equal volumes of all gases at the same temperature and pressure contain the same number of molecules'' is an expression of Avogadro's Law. This law is named after the Italian scientist Amedeo Avogadro, who discovered that the volume of a gas is directly proportional to the number of molecules or atoms present, provided that the temperature and pressure remain constant. This law can be used to determine the molar volume of gases and is important in many fields of science, such as chemistry and physics. In simple terms, this law states that two gases at the same temperature and pressure will have the same number of molecules in a given volume, regardless of their chemical identity or atomic/molecular weight.

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Kinetic Theory Of Matter And Gas Laws

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Question 35 Report

Which of the following equations represents a neutralization reaction?

CaCI₂ + 2HCI →CI₂ +CaCI ₂ + H₂O

Na₂O₂ + H₂SO₄ → Na₂SO₄ + H₂O₂

H₂SO₄ + KOH → KHSO₄ + H₂ O

2Na + 2H₂O → 2NaOH + H₂

CuSO₄ + 2NaOH → Cu(OH)₂+ Na₂SO₄

Answer Details

The equation that represents a neutralization reaction is: H₂SO₄ + KOH → KHSO₄ + H₂ O. In this reaction, an acid (H₂SO₄) reacts with a base (KOH) to form a salt (KHSO₄) and water (H₂O). Neutralization reactions involve the combination of an acid and a base to form a salt and water, with the acid and base neutralizing each other's acidic and basic properties. The other options either do not involve an acid and a base or do not form a salt and water, and thus do not represent neutralization reactions.

Read lesson note on Periodic Chemistry (Ghana Only) (WAEC)