JAMB UTME - Chemistry - 2018

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Question 2 Report

In the shown experiment (Fig. 1) the litmus paper will initially

be bleached

turn green

turn red

turn blue

Acids, Bases And Salts

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Question 3 Report

The periodic classification is an arrangement of the elements

atomic weights

isotopic weights

molecular weights

atomic numbers

Answer Details

The periodic classification is an arrangement of the elements based on their atomic numbers. The periodic table is a chart that lists all the known chemical elements in order of increasing atomic number, arranged in rows and columns according to their electronic structure and chemical properties. The atomic number of an element is the number of protons in the nucleus of an atom of that element. Each element has a unique atomic number, which determines its position in the periodic table. The elements are arranged in rows called periods, and in columns called groups or families. Elements in the same group have similar properties because they have the same number of valence electrons, which are the electrons in the outermost shell of the atom. The periodic table is an incredibly useful tool for chemists because it allows them to predict the properties of elements based on their position in the table. For example, elements in the same group tend to form similar compounds, so if you know the properties of one element in a group, you can often predict the properties of the other elements in that group. In summary, the periodic classification is an arrangement of the elements based on their atomic numbers. The periodic table is a chart that organizes the elements into rows and columns based on their electronic structure and chemical properties, allowing scientists to make predictions about the behavior of the elements based on their position in the table.

Read lesson note on Atomic Structure And Bonding (JAMB)

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Question 4 Report

Which of the following produces relatively few ions in solution?

NaOH

Ca(OH)

_{2}

KOH

AI(OH)

_{3}

Answer Details

The correct answer is AI(OH)3. When ionic compounds dissolve in water, they dissociate into their constituent ions, producing charged particles in solution. The more ions a compound produces, the more conductive it is in solution. AI(OH)3, also known as aluminum hydroxide, produces relatively few ions in solution because it is a weak base. When AI(OH)3 dissolves in water, it releases a small amount of Al3+ and OH- ions. In contrast, NaOH, KOH, and Ca(OH)2 are strong bases that dissociate more completely in water and produce more ions in solution. NaOH and KOH produce one hydroxide ion for every sodium or potassium ion, while Ca(OH)2 produces two hydroxide ions for every calcium ion. Therefore, of the options listed, AI(OH)3 produces relatively few ions in solution.

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

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Question 5 Report

A substance that is used as a ripening agent for fruits is

ethene

propane

methane

butane

Answer Details

The substance that is commonly used as a ripening agent for fruits is ethene. Ethene, also known as ethylene, is a natural plant hormone that is produced by fruits, especially during the ripening process. It is a colorless gas that can be easily synthesized and used as a ripening agent for fruits. When fruits are exposed to ethene, it triggers a series of biochemical reactions that accelerate the natural ripening process. This can help fruits to ripen faster and more uniformly, which is important for commercial purposes where fruits need to be sold quickly. The use of ethene as a ripening agent is regulated by food safety agencies, as excessive exposure to ethene can cause over-ripening and spoilage of fruits. However, when used in appropriate concentrations, ethene is a safe and effective way to promote the ripening of fruits.

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

Acids, Bases And Salts

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Question 6 Report

A basic postulate of the kinetic theory of gases is that the molecules of a gas move in straight lines between collisions. This implies that

collisions are perfectly elastic

forces of repulsion exis

forces of repulsion and attraction are in equilibrium

collisions are inelastic

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Question 7 Report

To what volume must \(300\text{cm}^3\) of 0.60M sodium hydroxide solution be diluted to give a 0.40M solution?

450cm

^{3}

300cm

^{3}

200cm

^{3}

150cm

^{3}

SOLUBILITY OF SUBSTANCES (Nigeria Only)

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Question 8 Report

According to Charles' law, the volume of a gas becomes zero at

0°C

-100°C

-273°C

-373°C

Answer Details

Charles' law states that the volume of a gas is directly proportional to its temperature, provided that the pressure remains constant. This means that as the temperature of a gas increases, its volume also increases. However, it is important to note that this law only applies to ideal gases, which are theoretical gases that perfectly follow the laws of thermodynamics. According to Charles' law, the volume of a gas becomes zero at absolute zero, which is approximately -273°C. At this temperature, the gas particles would have no kinetic energy and would be in their lowest energy state. The volume of a real gas would not actually become zero at absolute zero because the gas particles would have some residual intermolecular interactions that would prevent them from completely collapsing to a single point.

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

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Question 9 Report

The type of bonding in \(\left[\mathrm{Cu}(\mathrm{NH}_3)_4\right]^{2+}\) is

coordinate

electrovalent

metallic

covalent

Answer Details

The type of bonding in [Cu(NH3)4]2+ is coordinate bonding. Coordinate bonding (also known as dative covalent bonding) is a type of covalent bonding where one atom (in this case, the nitrogen atom in NH3) donates a pair of electrons to another atom or ion (in this case, the copper ion Cu2+). The donating atom is called the ligand, and the receiving atom or ion is called the central metal ion. In [Cu(NH3)4]2+, each ammonia molecule (NH3) donates a lone pair of electrons on the nitrogen atom to the copper ion, forming four coordinate bonds between the ligands and the central copper ion. The presence of coordinate bonds is indicated by the use of square brackets around the coordination compound, and the charge on the compound is indicated by the superscript outside the brackets. Therefore, the answer is option A: coordinate.

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Question 10 Report

Diamond is a bad conductor of electricity because its bonding electrons are used in

crystal lattice formation

covalent bond formation

metallic bond formation

coordinate bond formation

Answer Details

Diamond is a bad conductor of electricity because of its unique structure and bonding. The carbon atoms in diamond form a covalent network, where each carbon atom is bonded to four other carbon atoms. These bonds are strong and hold the atoms in a rigid three-dimensional structure called a crystal lattice. In a covalent bond, atoms share electrons to form a stable compound. In diamond, each carbon atom shares its valence electrons with four neighboring carbon atoms, forming a very strong covalent bond. All the valence electrons in the crystal lattice are used in covalent bond formation, which means there are no free or mobile electrons to carry an electric current. In other words, the electrons are tightly held in the covalent bonds, making it difficult for them to move around the crystal lattice and conduct electricity. In contrast, metals conduct electricity well because they have delocalized or free electrons that can move through the lattice of positively charged ions. So, diamond, being a covalent network solid, does not have free electrons that can carry an electric current, which is why it is a bad conductor of electricity.

Read lesson note on Atomic Structure And Bonding (JAMB)

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Question 11 Report

Methanoic acid mixes with water in all proportions and has about the same boiling point as water. Which of the following methods would you adopt to obtain pure water from a mixture of Sand, water and methanoic acid?

Fractional distillation

Filtration followed by distillation

Neutralization with sodium hydroxide followed by distillation

Neutralization with sodium hydroxide followed by filtration

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Question 12 Report

Which of the following metals cannot replace hydrogen from water or steam?

Sodium

Magnesium

Iron

Calcium

Metals And Their Compounds

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Question 13 Report

In the preparation of oxygen by heating KCIO\(_2\), in the presence of MnO\(_2\) only moderate heat is needed because the catalyst acts by

lowering the pressure of the reaction

increasing the surface area of the reaction

increasing the rate of the reaction

lowering the energy barrier of the reaction

Answer Details

The presence of MnO2 acts as a catalyst in the reaction of KCIO2 to produce oxygen. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the reaction itself. MnO2 acts by lowering the energy barrier of the reaction, which means it reduces the amount of energy required for the reaction to take place. This makes it easier for the reaction to occur, and thus the reaction proceeds at a faster rate. As a result, only moderate heat is needed to provide the initial energy required for the reaction to start. Therefore, the correct answer is: lowering the energy barrier of the reaction.

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

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Question 14 Report

A balanced chemical equation obeys the law of

conservation of mass

definite proportions

multiple proportions

conservation of energy

Answer Details

A balanced chemical equation obeys the law of conservation of mass. This means that in a chemical reaction, the total mass of the reactants must be equal to the total mass of the products. In other words, atoms cannot be created or destroyed during a chemical reaction, only rearranged. For example, if we burn a piece of wood, the mass of the ashes and the gases released will be equal to the mass of the original wood. This is because the atoms in the wood (carbon, hydrogen, oxygen, etc.) are rearranged during the burning process to form new molecules, but the total number of atoms remains the same. By balancing a chemical equation, we ensure that the same number and type of atoms are present on both sides of the equation, which satisfies the law of conservation of mass.

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

Read lesson note on Stoichiometry And Chemical Reactions (WAEC)

Stoichiometry And Chemical Reactions

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Question 15 Report

The conductivity of an acid solution depends on the

amount of ions present and their mobilities

mobilities of the ions present

amount of ions present

temperature of the solution

Answer Details

The conductivity of an acid solution depends on the amount of ions present and their mobilities. When an acid dissolves in water, it forms ions that can carry an electric charge. These ions are what allows the solution to conduct electricity. The more ions there are in the solution, the better it can conduct electricity. However, not all ions have the same mobility or ability to move around in the solution. Ions with a higher mobility can move more easily through the solution, leading to a higher conductivity. Therefore, the conductivity of an acid solution is determined by both the amount of ions present and their mobilities. Other factors such as temperature can also affect conductivity, but the primary factors are the amount and mobility of ions.

Read lesson note on Chemical Bonds (Ghana Only) (WAEC)

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

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

Chemical Bonds (Ghana Only)

Periodic Chemistry (Ghana Only)

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Question 16 Report

The collision theory explains reaction rates in terms of

size of the product

frequency of collision of the reactants

size of reactant

frequency of collision of the products

Answer Details

The collision theory explains reaction rates in terms of the frequency of collision of the reactants. In other words, the theory suggests that for a chemical reaction to occur, the reactant particles must collide with sufficient energy and with the correct orientation. The frequency of these collisions is an important factor in determining the rate of the reaction. The more frequently the reactant particles collide, the more likely it is that they will react and form products. Therefore, increasing the frequency of collisions between reactant particles can increase the rate of a chemical reaction. The size of the reactants or the products does not play a significant role in the collision theory.

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

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Question 17 Report

The Sulphide which is insoluble in dilute hydrochloric acid is

FeS

CuS

ZnS

Na2S

Answer Details

The sulphide which is insoluble in dilute hydrochloric acid is Copper Sulphide (CuS). When metal sulphides react with hydrochloric acid, they undergo an acid-base reaction to produce hydrogen sulphide gas and the corresponding metal chloride. For example, when Iron Sulphide (FeS) reacts with hydrochloric acid, it forms hydrogen sulphide gas (H2S) and iron chloride (FeCl2) as follows: FeS + 2HCl → H2S + FeCl2 However, Copper Sulphide (CuS) does not react with dilute hydrochloric acid, as it is insoluble in this acid. This is due to the fact that CuS is a much less reactive metal sulphide compared to FeS and ZnS, and therefore it does not undergo an acid-base reaction with dilute hydrochloric acid. In summary, CuS is the sulphide which is insoluble in dilute hydrochloric acid due to its low reactivity with acids.

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

Separation Of Mixtures And Purification Of Chemical Substances

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Question 18 Report

How many atoms are present in 6.0g of magnesium? [Mg = 24, N.A = \(6.02 \times 10^{23}\) mol]

1.20 x 10

^{22}

2.4 x 10

^{22}

1.51 x 10

^{22}

3.02 x 10

^{22}

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Question 19 Report

The presence of ammonia gas in a desiccator can exclusively be removed by

phosphorus (V) oxide

fused calcium chloride

calcium chloride

concentrated tetraoxosulphate (VI) acid

Oxidation And Reduction

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Question 20 Report

If the molecular mass of tetraoxosulphate (VI) acid is 98, calculate its vapour density

196

49

106

82

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Question 21 Report

From the graph above, it may be concluded that

AgNO

_{3}

is probably not soluble at 1100

NaCl is insoluble in water

Pb(NO

_{3}

)

_{2}

is more soluble than KCIO

_{3}

The solubility of KCIO

_{3}

exceeds that of NaCl at all temperature

Solubility Of Substances (Ghana Only)

Solutions

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Question 22 Report

Beryllium and Aluminium have similar properties because they

are both metals

belong to the same group

belong to the same period

are positioned diagonally to each other

Metals And Their Compounds

Non-metals And Their Compounds

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Question 23 Report

A given amount of gas occupies \(10.0\mathrm{dm}^{5}\) at 4atm and 273°C. The number of moles of the gas present is [Molar volume of gas at s.t.p = \(22.4\mathrm{dm}^{3}\)]

0.89 mol

1.90 mol

3.80 mol

5.70 mol

Answer Details

The ideal gas law is PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is temperature. We can use this equation to solve for the number of moles of gas present. First, we need to convert the volume from dm5 to dm3, which is the same as liters (L). So, 10.0 dm5 is equal to 10.0/1000 = 0.01 dm3 or 0.01 L. Next, we need to convert the temperature from Celsius to Kelvin by adding 273 to get 546 K. Now we can plug in the values we have into the ideal gas law: 4 atm x 0.01 L = n x 0.0821 L·atm/K·mol x 546 K Simplifying, we get: 0.04 = n x 44.8 Solving for n, we get: n = 0.04/44.8 = 0.00089 mol Finally, we can compare this value to the molar volume of a gas at standard temperature and pressure (STP), which is 22.4 L/mol. To do this, we need to convert the volume of gas we have to STP conditions. Since the temperature is already at STP (273 K), we just need to adjust the pressure. Using the ideal gas law, we can solve for the volume at STP: 1 atm x V = 0.00089 mol x 0.0821 L·atm/K·mol x 273 K Simplifying, we get: V = 0.0224 L or 22.4 dm3 Therefore, the amount of gas present is equal to 0.00089 mol, which is less than 1 mol. So the answer is 0.89 mol.

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

Read lesson note on Stoichiometry And Chemical Reactions (WAEC)

Read lesson note on States Of Matter (WAEC)

Stoichiometry And Chemical Reactions

States Of Matter

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Question 24 Report

The ionic radii of metals are usually

greater than their atomic radii

unaffected by the charge on the ion

the same as their atomic radii

less than their atomic radii

Answer Details

The ionic radii of metals are usually smaller than their atomic radii. The size of an atom is determined by the distance between the nucleus and the outermost electrons, which is known as the atomic radius. When a metal atom loses one or more electrons to form a positive ion (or cation), the resulting ion has a smaller size than the original atom. This is because the positive charge of the ion attracts the remaining electrons closer to the nucleus, making the ion smaller in size. So, when a metal forms a cation, its ionic radius is typically smaller than its atomic radius. This is a general trend in the periodic table, although there are some exceptions.

Read lesson note on Atomic Structure And Bonding (JAMB)

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Question 25 Report

The derivative of benzene that can be used in making explosives is

aniline

xylene

phenol

toluene

Chemistry Of Carbon Compounds (Nigeria Only)

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Question 26 Report

The Consecutive members of an alkane homologous series differ by

CH

_{2}

CH

_{3}

C

_{n}

H

_{n}

Answer Details

The consecutive members of an alkane homologous series differ by a CH2 unit. This means that each successive member of the alkane series has one more CH2 unit than the previous member. For example, consider the simplest alkane, methane (CH4). The next member of the series is ethane (C2H6), which differs from methane by one CH2 unit. The next member after that is propane (C3H8), which differs from ethane by another CH2 unit. This pattern continues for all members of the alkane homologous series. The reason for this is that each carbon atom in the alkane chain must be bonded to four other atoms, which are usually hydrogen atoms. This means that each carbon atom in the chain can only bond to one other carbon atom. Therefore, the length of the alkane chain can only increase by adding CH2 units to the end of the chain. In summary, the consecutive members of an alkane homologous series differ by a CH2 unit because this is the only way to add length to the alkane chain while maintaining the required number of bonds for each carbon atom in the chain.

Read lesson note on Chemical Equilibria (JAMB)

Chemical Equilibria

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Question 27 Report

\( \mathrm{H_2S(g) + Cl_2(g) \rightarrow 2HCl(g) + S(g)} \)

In the reaction above, the substance that is reduced is

H

_{2}

S

HCl

Cl

_{2}

Oxidation And Reduction

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Question 28 Report

When air which contains the gases Oxygen, nitrogen, carbondioxide, water vapour and the rare gases, is passed through alkaline pyrogallol and then over quicklime, the only gases left are;

nitrogen and carbondioxide

the rare gases

nitrogen and oxygen

nitrogen and the rare gases

Air

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Question 29 Report

The refreshing and characteristic taste of soda water and other soft drinks is as a result of the presence of

carbon(IV)oxide

carbon(ll)oxide

soda

glucose

Acids, Bases And Salts (Nigeria Only)

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Question 30 Report

The end products of burning a candle in the atmosphere are water and

carbon (II) oxide

sulphur (IV) oxide

carbon (IV) oxide

sulphur (VI) oxide

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Question 31 Report

At what temperature is the solubility of potassium trioxonitrate(V ) equal to that of sodium trioxonitrate (V)?

0

^{o}

c

30

^{o}

c

40

^{o}

c

45

^{o}

c

Solubility

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Question 32 Report

In the reaction between sodium hydroxide and sulphuric acid solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralise 10cm3 of 1.25 molar sulphuric acid?

5cm

^{3}

10cm

^{3}

20cm

^{3}

50cm

^{3}

Stoichiometry And Chemical Reactions

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Question 33 Report

(I). \(3\mathrm{CuO}(s) + 2\mathrm{NH}_3(g) \longrightarrow 3\mathrm{Cu}(s) + 3\mathrm{H}_2\mathrm{O}(l) + \mathrm{N}_2(g)\)

(II). \(2\mathrm{NH}_3(g) + 3\mathrm{Cl}_2(g) \longrightarrow 6\mathrm{HCl}(g) + \mathrm{N}_2(g)\)

(III). \(4\mathrm{NH}_3(g) + 3\mathrm{O}_2(g) \longrightarrow 6\mathrm{H}_2\mathrm{O}(l) + \mathrm{N}_2(g)\)

The reactions represented by the equations above demonstrate the

basic properties of ammonia

acidic properties of ammonia

reducing properties of ammonia

oxidizing properties of ammonia

Chemical Combination

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Question 34 Report

The knowledge of half-life can be used to

Create an element

Detect an element

Split an element

Irradiate an element