JAMB UTME - Chemistry - 2021

Maelezo ya Majibu

The mass number of a nucleus is the sum of the number of protons and neutrons present in the nucleus. These particles, protons and neutrons, are the building blocks of the nucleus and make up its atomic mass. The mass number is an important characteristic of an atom and helps to distinguish it from other atoms of the same element. For example, two isotopes of carbon, carbon-12 and carbon-14, have different mass numbers even though they both have 6 protons. It's worth noting that the mass number is not always greater than the atomic number, but it is always greater than or equal to the atomic number. The atomic number of an atom is simply the number of protons in its nucleus, and it determines what element the atom is.

Maelezo ya Majibu

Heat capacity or thermal capacity: The amount of heat to be supplied to an object to produce a unit change in its temperature(

Maelezo ya Majibu

I and II are chemical changes. A chemical change is a transformation in which a substance undergoes a chemical reaction to form a new substance with different properties. Cooking of food and digestion of food are examples of chemical changes because the chemical composition of the food changes as it is cooked or digested. Freezing of water is a physical change, not a chemical change. Freezing is a change of state from a liquid to a solid, but the chemical composition of the water remains the same. Heating of water is also a physical change, not a chemical change. Heating causes the water molecules to move faster, but the chemical composition of the water remains the same.

Maelezo ya Majibu

The most abundant rare gas in the atmosphere is Argon (Ar). Rare gases, also known as noble gases, are a group of chemical elements that are found in the atmosphere in small amounts. The rare gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Of these, argon is the most abundant, making up approximately 0.934% of the Earth's atmosphere. Argon is an odorless, colorless, and tasteless gas that is chemically inert, meaning it does not easily react with other chemical species. This makes it useful in a variety of industrial and scientific applications, such as in the production of electric lamps and in welding. Despite its abundance, argon is still considered a rare gas because it is relatively scarce compared to other atmospheric gases, such as nitrogen and oxygen, which make up the majority of the Earth's atmosphere.

Maelezo ya Majibu

The nucleus of a hydrogen atom consists of only one proton. Hydrogen is the simplest and lightest element, and its nucleus is made up of only one positively charged particle, the proton. The proton is located at the center of the hydrogen atom, and it is surrounded by one electron, which is negatively charged. Neutrons, which are neutral particles, are also found in the nuclei of other elements, but not in the hydrogen atom. Hydrogen has only one electron, and it is located in the electron cloud surrounding the nucleus. So, to summarize, the nucleus of a hydrogen atom consists of only one proton, and it does not contain any neutrons or electrons.

Maelezo ya Majibu

Copper is the only metal that has been scientifically proven to have anti-bacterial properties. Copper has the ability to kill bacteria by damaging their cell walls, which leads to the death of the bacteria. This is why copper is often used in items that need to be kept clean and hygienic, such as door handles, kitchen utensils, and medical equipment. Copper's anti-bacterial properties make it a popular choice for preventing the spread of germs and infections.

Maelezo ya Majibu

The process of extracting a metal from its ore and refining it is called metallurgy. This is the scientific and technical process of extracting metals from their ores, purifying them, and preparing them for use. This can include various steps such as crushing and grinding the ore, concentrating the metal, and finally refining it to obtain the pure metal. Metallurgy is an important field that combines science, engineering, and technology to produce metals that are essential for various industries and applications. It plays a critical role in modern society and is used to produce a wide range of metals including copper, aluminum, iron, and gold, among others.

Maelezo ya Majibu

The phenomenon you're referring to is called sublimation. Sublimation is the process by which a solid substance directly turns into a gas, bypassing the liquid stage. This happens when the solid substance is exposed to air and the temperature is high enough to cause the particles in the solid to turn into a gas. For example, camphor and naphthalene are commonly used as air fresheners and moth repellents, and they tend to disappear over time because they sublime when exposed to air. Dry ice, which is the solid form of carbon dioxide, also sublimes at normal atmospheric pressure. So, in a nutshell, sublimation is the process of a solid turning directly into a gas without becoming a liquid first.

Maelezo ya Majibu

The process you are referring to is called Hydrolysis. Hydrolysis is a chemical reaction in which water reacts with a salt to form an acid or a base. In this reaction, the water molecule splits into hydrogen (H+) and hydroxide (OH-) ions, which then react with the salt to form an acid or a base. For example, if a salt of a weak acid is hydrolyzed, the reaction will produce a weak acid and a weak base. On the other hand, if a salt of a strong acid is hydrolyzed, the reaction will produce a strong acid and a strong base. Overall, hydrolysis is an important process that helps to regulate the acid-base balance in the body and the environment.

Maelezo ya Majibu

The two types of pollutants in the troposphere are gaseous and particulate pollutants. The troposphere is the lowest layer of the Earth's atmosphere, and it is where we live and breathe. It is where weather occurs, and it is also where most air pollution takes place. Gaseous pollutants are gases that are harmful to human health and the environment. Examples of gaseous pollutants include carbon monoxide, sulfur dioxide, and nitrogen oxides. These gases can come from sources such as power plants, transportation, and industrial processes. Particulate pollutants are tiny particles suspended in the air. They can come from sources such as dust, soot, and smoke. Particulate matter can have a range of negative impacts on human health, including respiratory and cardiovascular problems. In conclusion, the two main types of pollutants in the troposphere are gaseous and particulate pollutants.

Maelezo ya Majibu

Soaps clean surfaces based on the principle of surface tension. Surface tension is the property of a liquid that makes it behave as if its surface is a stretched elastic membrane. Soaps work by reducing the surface tension of water, allowing it to better penetrate and lift dirt and oils from surfaces. The soap molecules have a polar (hydrophilic) end that attracts water and a non-polar (hydrophobic) end that repels water. When soap is added to water, the soap molecules surround and lift dirt and oils from surfaces, breaking the surface tension of the water and allowing it to wash away dirt and oils more effectively. Therefore, soaps clean surfaces based on the principle of surface tension.

Maelezo ya Majibu

Mass of Solution = Mass of Solute + Mass of Solvent → 20g + 180g

: Mass of Solution = 200g

Mass Percent = MassofSoluteMassofSolution∗100 $\frac{MassofSolute}{MassofSolution}\ast 100$

Mass percent = 20200∗100 $\frac{20}{200}\ast 100$

Mass percent = 10%

Maelezo ya Majibu

The metal used to recover copper from a solution of copper sulfate is iron (Fe). In a process known as electrolysis, iron acts as the cathode (negative electrode) and attracts positively charged copper ions in the solution. At the iron cathode, the copper ions gain electrons and are reduced to solid copper metal, which is deposited on the surface of the iron cathode. Therefore, iron is the metal used to recover copper from a solution of copper sulfate.

Maelezo ya Majibu

The mass of one Avogadro number of helium atoms is 4.00 grams. Avogadro's number is a fundamental constant in physics and chemistry, and it represents the number of atoms or molecules in one mole of a substance. One mole of a substance is defined as the amount of a substance that contains the same number of entities (atoms, molecules, or other particles) as there are in 12 grams of pure carbon-12. The mass of one Avogadro number of helium atoms depends on the atomic mass of helium, which is approximately 4 atomic mass units. Therefore, one Avogadro number of helium atoms weighs approximately 4 grams.

Maelezo ya Majibu

The common name for the compound (CH3)3CBr is Isobutyl Bromide. Isobutyl bromide is a colorless liquid with a sweet odor. It is used as a solvent and intermediate in the manufacture of various chemicals, including pharmaceuticals, dyes, and perfumes. The name "isobutyl" indicates that the molecule has a structural formula in which there are three carbon atoms in a straight chain and one of the carbons is bonded to a branched carbon group (-CH(CH3)2). The suffix "-bromide" indicates that the molecule contains a bromine atom.

Maelezo ya Majibu

All of the options I, II, III, and IV are forms of calcium carbonate. Calcium carbonate is a naturally occurring compound that is commonly found in rocks and minerals. - Limestone is a sedimentary rock made mostly of calcium carbonate. It is often used as a building material, as well as an industrial mineral in the production of cement and other products. - Marble is a metamorphic rock that is formed from the recrystallization of limestone under high temperatures and pressures. It is prized for its beauty and is often used in sculptures and building materials. - Chalk is a soft, white form of calcium carbonate that is commonly used as a writing material. - Eggshells are made mostly of calcium carbonate, which provides the strength and structure needed to protect the egg and its contents. In conclusion, all four options are forms of calcium carbonate.

Maelezo ya Majibu

The atomic weight of nitrogen is 14. Atomic weight, also known as atomic mass, is the measure of the mass of an atom. It is expressed in atomic mass units (amu) and is the weighted average of the masses of all the naturally occurring isotopes of an element. For nitrogen, the most abundant isotope has an atomic weight of 14 amu, which makes the atomic weight of nitrogen 14 amu. This means that, on average, one nitrogen atom weighs 14 atomic mass units. It's important to note that atomic weight is different from atomic number, which is the number of protons in the nucleus of an atom and determines the chemical identity of the element.

Maelezo ya Majibu

A chemical process in which there is a gain of electrons is known as "Reduction". In simple terms, reduction is the process of adding electrons to a chemical species. This often results in the formation of a new substance with different properties than the original substance. The opposite of reduction is oxidation, which is the process of removing electrons from a chemical species. In reduction reactions, the species that gains electrons is referred to as the "reductant," while the species that loses electrons is referred to as the "oxidant." The transfer of electrons from the oxidant to the reductant results in a reduction in the oxidation state of the reductant and an increase in the oxidation state of the oxidant.

Maelezo ya Majibu

The element with atomic number 17 is Chlorine. Chlorine is a member of the halogen group of elements, which also includes Fluorine (atomic number 9), Bromine (atomic number 35), Iodine (atomic number 53), and Astatine (atomic number 85). These elements are characterized by having seven electrons in their outermost shell, which makes them highly reactive. Of the options given, Bromine is most similar to Chlorine in terms of their chemical properties and electron configuration. Both Chlorine and Bromine are members of the same group in the periodic table and have similar electron configurations, which makes them have similar chemical properties. Both are reactive elements and form compounds with a variety of other elements, including metals, nonmetals, and other halogens. Therefore, the element with atomic number 17 (Chlorine) will resemble the element with atomic number 35 (Bromine) the most.

Maelezo ya Majibu

The gas that causes global warming is Carbon Dioxide (CO2). It is a colorless, odorless gas that is produced when we burn fossil fuels, such as coal, oil, and natural gas. These fuels are the primary source of energy for electricity, transportation, and heating, but the burning of these fuels releases large amounts of CO2 into the atmosphere. The CO2 builds up in the atmosphere and acts like a blanket, trapping heat from the sun and causing the earth's temperature to rise. This is known as the greenhouse effect, and it is leading to climate change and global warming.

Maelezo ya Majibu

Oxygen is absent in Kerosene. Kerosene is a type of fuel oil that is commonly used as a fuel for lamps, heaters, and jet engines. It is a clear, colorless liquid that is derived from petroleum and is composed primarily of hydrocarbons, which are molecules made up of only carbon and hydrogen atoms. Since kerosene does not contain oxygen, it is not a renewable source of energy and must be refined from petroleum. In contrast, soil, glass, and cement all contain oxygen, as they are composed of various compounds that contain oxygen as an essential component. Soil, for example, contains a variety of minerals and organic matter that are held together by oxygen and other chemical bonds. Glass is made up of silicates, which are compounds containing oxygen and silicon, while cement is composed of calcium silicates and other compounds that contain oxygen.

Maelezo ya Majibu

The compounds made up of only carbon and hydrogen are called Hydrocarbons. A hydrocarbon is a type of organic compound that consists solely of hydrogen and carbon atoms. These compounds can range from simple molecules like methane to complex, large molecules like gasoline. They play a crucial role in many industries, including the energy, petrochemical, and pharmaceutical sectors.

Maelezo ya Majibu

The earliest developed breathalyzer was based on reaction of alcohol if present in the exhaled air with a cocktail of chemicals containing sulfuric acid, potassium dichromate, silver nitrate, and water. Silver nitrate catalyzes the reaction between alcohol and potassium dichromate in acidic medium.

Maelezo ya Majibu

The reactivity of Fluorine (F) is due to its high electronegativity. Electronegativity is a measure of the ability of an atom to attract electrons towards itself. Fluorine has the highest electronegativity of all elements, which means it strongly attracts electrons towards itself. This makes it highly reactive, especially with elements that have a low electronegativity, such as metals. Fluorine's small size also contributes to its reactivity. Smaller atoms generally have higher electronegativities and are more reactive than larger atoms. The availability of D-orbitals in fluorine also contributes to its reactivity. D-orbitals are involved in chemical reactions and can participate in the formation of bonds between atoms. So, to summarize, the reactivity of Fluorine is due to its high electronegativity, small size, and the availability of D-orbitals. The strong F-F bond is not a factor that directly contributes to the reactivity of Fluorine.

Maelezo ya Majibu

Bromine is a non-metal that remains liquid at room temperature. Bromine is a chemical element with the symbol Br and atomic number 35. It is a non-metal and is one of the only two elements (the other being mercury) that are liquid at room temperature and standard pressure. This means that, at temperatures commonly found in most environments, bromine is a liquid and does not exist as a solid or gas. It's important to note that while bromine is a liquid at room temperature, it is still a highly reactive element and can cause serious health hazards if not handled properly. Therefore, it is important to take necessary precautions when working with bromine.

Maelezo ya Majibu

One of the following options is not a physical property of monosaccharides: - They are highly vital to the exploration of metals Monosaccharides are simple sugars that play important roles in biology and biochemistry. They are characterized by several physical properties: - Monosaccharides get charred when heated, meaning that they undergo a chemical reaction when exposed to high temperatures and form a black, charred residue. - Monosaccharides are water-soluble, sweet substances, which means that they dissolve in water and have a sweet taste. Examples of monosaccharides include glucose, fructose, and galactose. - They can be reduced to sugar alcohols, meaning that they can undergo a chemical reduction reaction and form compounds known as sugar alcohols. In conclusion, the option "They are highly vital to the exploration of metals" is not a physical property of monosaccharides.

Maelezo ya Majibu

The molar enthalpy change accompanying the removal of an electron from a gas phase atom or ion in its ground state is called Ionization Enthalpy. Ionization Enthalpy refers to the amount of energy required to remove one electron from an atom or ion in its ground state to form a positively charged ion. In other words, it is the energy required to "ionize" an atom or ion. For example, to remove an electron from a neutral hydrogen atom to form a positive hydrogen ion (H+) requires a certain amount of energy. This energy is called the ionization enthalpy of hydrogen. Similarly, the ionization enthalpy can be defined for any other atom or ion.

Maelezo ya Majibu

The enzyme that converts glucose to ethyl alcohol is called Zymase. Zymase is a complex mixture of several enzymes produced by yeast cells that help break down glucose into alcohol and carbon dioxide. During the process of fermentation, yeast cells consume glucose and release alcohol and CO2 as waste products. The zymase enzymes are crucial for this process, as they catalyze the chemical reaction that transforms glucose into ethyl alcohol. This process is used in the production of alcoholic beverages, such as beer and wine.

Maelezo ya Majibu

The nucleus of an atom consists of protons and neutrons. These two particles are found in the center of an atom, and they are responsible for determining the chemical properties of an element. Protons are positively charged particles, and neutrons are neutral particles that have no charge. Together, these particles make up the nucleus of an atom, which is usually much smaller than the overall size of the atom. The number of protons in an atom is called the atomic number, and it determines what element the atom is. For example, all hydrogen atoms have one proton in their nucleus, and all helium atoms have two protons.

Maelezo ya Majibu

Reactions involving simultaneous oxidation and reduction are called redox reactions. In a redox reaction, one species is oxidized (loses electrons) and another species is reduced (gains electrons). These two processes happen simultaneously and are always linked. The species that is oxidized becomes a better oxidizing agent, while the species that is reduced becomes a better reducing agent. Redox reactions are important in many biological, chemical and physical processes, including cellular respiration, corrosion, and electrochemistry. Therefore, reactions involving simultaneous oxidation and reduction are called redox reactions.

Maelezo ya Majibu

The scientist who stated that matter can be converted into energy is Albert Einstein. Einstein is famous for his theory of special relativity, in which he famously formulated the equation E=mc^2. This equation states that energy (E) and mass (m) are interchangeable and that energy can be converted into matter and vice versa at a constant speed of light (c). This idea was groundbreaking and helped to lay the foundations for the development of nuclear energy and modern physics. Therefore, Albert Einstein is the scientist who stated that matter can be converted into energy.

Maelezo ya Majibu

Propyne (methylacetylene) is an alkyne with the chemical formula HC≡ $\equiv$CCH3

Maelezo ya Majibu

A  mixture is a material made up of two or more different chemical substances which are not chemically combined. 

Mercury is a chemical element with the symbol Hg and atomic number 80.

Maelezo ya Majibu

The discovery of the neutron was made by James Chadwick in 1932. A neutron is a subatomic particle that is found in the nucleus of an atom. It has no electric charge, which makes it different from the other particles in the nucleus, the protons, which are positively charged. Chadwick discovered the neutron through a series of experiments that involved bombarding elements with alpha particles. He was able to show that there were particles in the nucleus that had no charge and concluded that these must be neutrons.

Maelezo ya Majibu

220g of carbon dioxide contains 6 moles. In chemistry, the number of moles of a substance can be calculated from its mass using the concept of molar mass. Molar mass is the mass of one mole of a substance and is usually expressed in units of grams per mole (g/mol). For carbon dioxide, the molar mass is 44.01 g/mol. To convert the mass of a substance to the number of moles, divide the mass by the molar mass. In this case, 220g / 44.01 g/mol = 5 moles.

Maelezo ya Majibu

The fourteen elements after actinium (atomic number 89) are called actinoids. Actinoids are a series of elements in the periodic table that are characterized by having similar chemical and physical properties, such as radioactive decay and the ability to form complex ions. Actinoids include elements such as thorium, protactinium, and uranium. Actinoids are also sometimes referred to as the actinide series.

Maelezo ya Majibu

The chemical name for the compound CuCO3 is Copper (ii) Carbonate. The number in parentheses after the name of the metal (Copper in this case) represents the oxidation state of the metal ion in the compound. The oxidation state of Copper in Copper (ii) Carbonate is +2, which is indicated by the Roman numeral "ii". So, the correct name for the compound CuCO3 is Copper (ii) Carbonate.

Maelezo ya Majibu

The N shell is the fourth orbit with 32 max number of electrons using 2n

Maelezo ya Majibu

The inherited traits of an organism are controlled by DNA (Deoxyribonucleic Acid) molecules. DNA is a long, double-stranded molecule that contains the genetic information of an organism. This genetic information is stored in the sequence of four types of nucleotides, which are the building blocks of DNA. The nucleotides are adenine (A), cytosine (C), guanine (G), and thymine (T). The sequence of these nucleotides determines the genetic code, which specifies the traits an organism inherits from its parents. When a cell divides, it copies its DNA so that each new cell gets a complete set of genetic instructions. This process is called DNA replication. During replication, enzymes help unwind the DNA double helix and make copies of each strand. The copies are then used to build new DNA molecules that are identical to the original. So, to summarize, the inherited traits of an organism are controlled by DNA molecules, which store the genetic information in the form of a specific sequence of nucleotides.

Maelezo ya Majibu

A binary compound of oxygen with another element is referred to as an oxide. An oxide is a chemical compound that contains oxygen and another element in its chemical formula. For example, water (H2O) is an oxide of hydrogen and oxygen, and carbon dioxide (CO2) is an oxide of carbon and oxygen. The term "oxide" is commonly used to describe compounds of oxygen with metals, but it can also refer to compounds of oxygen with non-metals.