JAMB UTME - Chemistry - 2018
Frage 2 Bericht
The Sulphide which is insoluble in dilute hydrochloric acid is
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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.
Frage 3 Bericht
The elements in the periodic table are listed in order of increasing
Frage 4 Bericht
The constituent common to duralumin and alnico is
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The common constituent found in both duralumin and alnico is aluminum (Al). Duralumin is an alloy made up of aluminum, copper, manganese, and magnesium. It is known for its high strength and light weight, making it useful in various applications such as aerospace and construction. Alnico, on the other hand, is an alloy made of aluminum, nickel, cobalt, iron, and small amounts of other elements. It is used in the production of strong permanent magnets for various applications such as in motors, generators, and loudspeakers. So, even though duralumin and alnico have different properties and uses, they both contain the element aluminum.
Frage 5 Bericht
At what temperature is the solubility of potassium trioxonitrate(V ) equal to that of sodium trioxonitrate (V)?
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Frage 6 Bericht
The reaction between an organic acid and an alcohol in the presence of an acid catalyst is known as;
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The reaction between an organic acid and an alcohol in the presence of an acid catalyst is known as esterification. Esterification is the process of forming an ester, which is a type of organic compound, from an alcohol and an acid. The acid catalyst is used to speed up the reaction by providing a proton to the reaction mixture, which helps to form the ester. Esterification results in the loss of a water molecule from the reaction mixture, which makes the reaction a type of dehydration reaction. However, it is important to note that esterification is a specific type of dehydration reaction where the products are an ester and an alcohol. So, the answer is esterification.
Frage 7 Bericht
2KClO3(g) MNO3? 2KCl(s) + 3O2(g)
The importance of the catalyst in the reaction above is that
Frage 8 Bericht
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?
Frage 9 Bericht
When large hydrocarbon molecules are heated at high temperature in the presence of a catalyst to give smaller molecules, the process is known as
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The process of breaking down large hydrocarbon molecules into smaller molecules by heating them at high temperatures in the presence of a catalyst is known as cracking. This process is used to convert heavy, high-molecular-weight hydrocarbon molecules into lighter, more valuable products such as gasoline and diesel fuel. The high temperatures cause the large molecules to break apart into smaller ones, and the catalyst helps speed up the reaction. This process is important in the petrochemical industry, as it allows for the production of a wider range of useful products from crude oil.
Frage 10 Bericht
To what temperature must a gas at 273k be heated in order to double both its volume and pressure?
Frage 11 Bericht
The collision theory explains reaction rates in terms of
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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.
Frage 12 Bericht
Which of the following are mixtures?
I. Petroleum
II. Rubber latex
III. Vulcanizer's solution
IV. Carbon sulphide
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Frage 13 Bericht
The refreshing and characteristic taste of soda water and other soft drinks is as a result of the presence of
Frage 14 Bericht
The number of electrons in the valence shell of an element of atomic number 14 is?
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The number of electrons in the valence shell of an element can be determined by using the periodic table and the electron configuration of the element. The valence shell is the outermost shell that contains electrons that are involved in chemical reactions. For an element with atomic number 14, which is silicon, the electron configuration is 1s2 2s2 2p6 3s2 3p2. The valence shell of silicon is the third shell, which contains 3s2 and 3p2 electrons. Therefore, the number of electrons in the valence shell of silicon is 4 electrons.
Frage 15 Bericht
In the preparation of oxygen by heating KCIO, in the presence of MnO2 only moderate heat is needed because the catalyst acts by 2
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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.
Frage 16 Bericht
2SO2 (g) + O2 (g) ↔ 2SO3 (g) ΔH = -395.7kJmol−1
In the equation, an increase in temperature will shift the equilibrium position to the
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Frage 17 Bericht
On which of the following is the solubility of a gaseous substance dependent?
I. Nature of solvent
II. Nature of solute
III. Temperature
IV. Pressure
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Frage 18 Bericht
The end products of burning a candle in the atmosphere are water and
Frage 19 Bericht
Which of the following pairs of substances will react further with oxygen to form a higher oxide?
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Frage 20 Bericht
In the laboratory preparation of oxygen, the gas cannot be collected by displacement of air because
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Frage 21 Bericht
The type of bonding in [Cu(NH3 )4 ]2+ is
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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.
Frage 22 Bericht
The figure above shows the electrolysis of molten sodium chloride. Z is the
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The figure shows the electrolysis of molten sodium chloride. During electrolysis, an electric current is passed through a molten or dissolved ionic compound to separate the ions. The positive ions move towards the negative electrode (cathode) and the negative ions move towards the positive electrode (anode). In the figure, the electrode connected to the positive terminal of the battery is the anode and the electrode connected to the negative terminal is the cathode. At the anode, the negatively charged chloride ions (Cl-) lose electrons and are oxidized to form chlorine gas (Cl2). At the cathode, the positively charged sodium ions (Na+) gain electrons and are reduced to form liquid sodium metal (Na). Therefore, the answer is (a) anode where the Cl- ions are oxidized. Z is the anode in the figure.
Frage 23 Bericht
If one of the following oxides is heated with hydrogen or carbon using a bunsen burner. it is not reduced to the metal, Which one is it?
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The oxide that cannot be reduced to the metal when heated with hydrogen or carbon using a Bunsen burner is magnesium oxide. Magnesium oxide is an ionic compound made up of positively charged magnesium ions and negatively charged oxygen ions. When heated with hydrogen or carbon, the oxygen ions are not easily removed from the compound. This is because the ionic bond between the magnesium and oxygen ions is very strong and requires a lot of energy to break. On the other hand, lead oxide, copper oxide, and tin oxide are all metal oxides and can be reduced to the metal by heating with hydrogen or carbon. This is because they have a weaker bond between the metal and oxygen ions, allowing the oxygen to be removed more easily when heated. In conclusion, magnesium oxide is the oxide that cannot be reduced to the metal when heated with hydrogen or carbon using a Bunsen burner.
Frage 25 Bericht
The presence of ammonia gas in a desiccator can exclusively be removed by
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Frage 26 Bericht
According to Charles' law, the volume of a gas becomes zero at
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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.
Frage 28 Bericht
The knowledge of half-life can be used to
Frage 29 Bericht
The conductivity of an acid solution depends on the
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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.
Frage 30 Bericht
The derivative of benzene that can be used in making explosives is
Frage 31 Bericht
A sample of hard water contains some calcium sulphate and calcium hydrogen carbonate. The total hardness may therefore be removed by
Frage 32 Bericht
The Consecutive members of an alkane homologous series differ by
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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.
Frage 33 Bericht
The situation obtained when a perfect gas expands into a vacuum is
Frage 34 Bericht
A given amount of gas occupies 10.0dm5 at 4atm and 273°C. The number of moles of the gas present is [Molar volume of gas at s.t.p = 22.4dm3
]
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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.
Frage 35 Bericht
The salt that reacts with dilute hydrochloric acid to produce a pungent smelling gas which decolourizes acidified purple potassium tetraoxomanganate (VII) solution is
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Frage 36 Bericht
The ionic radii of metals are usually
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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.
Frage 37 Bericht
Which of the compounds is composed of Al, Si, O and H?
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The compound composed of Al, Si, O and H is clay. Clay is a type of sedimentary rock that is made up of very small mineral particles, including hydrated aluminum silicates and other minerals such as quartz and feldspar. These minerals are rich in aluminum, silicon, oxygen, and hydrogen, which gives clay its unique chemical composition. Clay is formed through a process of weathering and erosion of rocks containing these minerals over a long period of time. As water and other natural forces break down the rocks, the mineral particles become suspended in water and are eventually deposited in sedimentary layers. Over time, these layers become compacted and cemented together, forming the solid clay deposits we see today. Therefore, the answer is option C: Clay.
Frage 38 Bericht
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;
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Frage 39 Bericht
Elements P, Q, R, S have 6, 11, 15, 17 electrons respectively, therefore,
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Elements form bonds with other elements in order to attain a stable electron configuration, like the one found in noble gases. There are two types of bonds: covalent and ionic (also called electrovalent). In covalent bonds, two elements share electrons to attain a stable electron configuration. This type of bond is formed between two non-metal elements. In ionic bonds, one element donates electrons to another element, creating ions. This type of bond is formed between a metal and a non-metal element. Based on the information given, we can deduce the following: - P is a metal, as it has only 6 electrons. - Q is a non-Metal, as it has 11 electrons. - R is a metal, as it has 15 electrons. - S is a non-Metal, as it has 17 electrons. So, from this information, we can conclude that: - P will form an ionic bond with R, as P is a metal and R is a metal. - Q will form a covalent bond with S, as Q is a non-Metal and S is a non-Metal. Therefore, the correct answer is "Q will form a covalent bond with S."
