JAMB UTME - Chemistry - 2015
Question 1 Report
Hydrogen can be displaced from a hot alkaline solution by
Answer Details
When a metal is placed into a hot alkaline solution containing hydrogen, the metal can displace the hydrogen from the solution. This is because metals have a higher affinity for electrons than hydrogen does. As a result, the metal will take the electrons from the hydrogen atoms, causing the hydrogen to be released from the solution. In this case, the metal that will displace the hydrogen most effectively is iron (Fe). Copper (Cu), calcium (Ca), and tin (Sn) can also displace hydrogen, but iron is the most effective of the four options.
Question 2 Report
Which of the following ions require the largest quantity of electricity for discharge at an electrode?
Question 3 Report
Atomicity of ozone is
Answer Details
The atomicity of ozone is 3. Atomicity refers to the number of atoms present in a molecule of a substance. For example, in oxygen gas (O2), the atomicity is 2 because there are 2 oxygen atoms in a molecule of O2. Ozone (O3) is a molecule made up of 3 oxygen atoms. This means that the atomicity of ozone is 3, because there are 3 atoms in each molecule of ozone. It's important to note that atomicity is different from the chemical formula of a substance. The chemical formula of ozone is O3, which tells us that there are 3 oxygen atoms present in a molecule of ozone. But the atomicity specifically refers to the number of atoms in a single molecule of a substance.
Question 4 Report
When sugar is dissolved in tea, the reaction is always accomplished by
Answer Details
Question 5 Report
Iron is often galvanized in order to
Answer Details
Iron is often galvanized in order to protect it against corrosion. Galvanizing involves coating the surface of iron with a layer of zinc. Zinc is more reactive than iron, which means that when the iron is exposed to oxygen and water, the zinc sacrificially corrodes instead of the iron. This protects the iron from rust and other forms of corrosion, which can weaken and damage the metal. The zinc layer also acts as a barrier between the iron and the environment, helping to prevent moisture and other corrosive substances from reaching the iron surface. As a result, galvanized iron is often used in outdoor applications where it is exposed to moisture and other corrosive elements, such as fences, roofs, and gutters.
Question 6 Report
The substance that is used in the steel industry for the removal of carbon, sulphur and phosphorus impurities from pig iron is
Answer Details
The substance used in the steel industry for the removal of carbon, sulphur, and phosphorus impurities from pig iron is oxygen. This process is called "oxidation" and it occurs when oxygen reacts with the impurities in the pig iron, which then form oxides that can be easily removed. During the steelmaking process, pig iron is melted in a furnace and then impurities such as carbon, sulphur, and phosphorus are removed. Oxygen is blown into the furnace, which reacts with the impurities to form oxides. These oxides rise to the surface of the molten metal and form a slag layer, which is removed. This process results in the production of steel with lower impurity levels and higher purity. In summary, oxygen is used in the steel industry for the removal of impurities from pig iron through the process of oxidation, which forms oxides that can be easily removed.
Question 7 Report
Which of the activities is commonly used as a nuclear fuel
Answer Details
Uranium is commonly used as a nuclear fuel. Uranium is a naturally occurring metal that has some unique properties that make it suitable for use in nuclear reactors. One of these properties is that uranium atoms can be easily split apart, or "fissioned," when they are bombarded with neutrons. This fission process releases a tremendous amount of energy, which can be harnessed to generate electricity in nuclear power plants. In nuclear reactors, uranium fuel is typically in the form of pellets that are loaded into metal tubes called fuel rods. These fuel rods are then arranged in a specific pattern in the reactor core. When the reactor is operating, the fuel rods heat up as the uranium atoms undergo fission, and this heat is used to generate steam, which in turn drives a turbine to produce electricity. While other elements such as thorium can also be used as nuclear fuel, uranium is the most commonly used fuel in nuclear power plants due to its availability and ease of use.
Question 8 Report
In the industrial production of H2 is removed by (solution)
Answer Details
Washing under pressure is an action in the industrial production of H. Options B,C,D will not yield Co and H
Question 9 Report
Cu2S(s) + O2(g) = 2CU(s) + SO22(g)
Answer Details
The oxidation number is from h to O as a result of release of sulphur. Option B, C, D are not the actual oxidation number for copper
Question 10 Report
Flow of current in electrolytes is due to the movement of
Answer Details
The flow of current in electrolytes is due to the movement of ions. An electrolyte is a substance that conducts electricity when dissolved in water or melted. When an electrolyte dissolves in water, it breaks down into positively charged ions (cations) and negatively charged ions (anions). These charged ions can move freely within the solution and are attracted to oppositely charged ions. When a potential difference (voltage) is applied across the electrolyte solution, the positively charged ions move towards the negatively charged electrode (cathode), and the negatively charged ions move towards the positively charged electrode (anode). This movement of ions creates an electric current, which is the flow of charged particles through the electrolyte solution. It is important to note that the movement of ions in electrolytes is different from the flow of electrons in conductors. In conductors, such as metals, electrons are the charged particles that move to create an electric current.
Question 11 Report
Vulcanization involves the removal of
Answer Details
Vulcanization involves the creation of chemical bonds between rubber molecules by cross-linking them with sulfur or other chemicals. This process helps to increase the strength, durability, and elasticity of the rubber. During vulcanization, the double bonds in the rubber molecules are broken and new cross-links are formed, which results in the formation of a polymer network. Therefore, the answer is the double bond, as it is removed or broken during the process of vulcanization.
Question 12 Report
The fuming of kettles is caused by the presence in the water of
Answer Details
The fuming of kettles is caused by the presence of calcium trioxocarbonate (IV) in the water. This compound is also known as calcium carbonate and is commonly found in hard water. When hard water is heated in a kettle, the calcium carbonate reacts with the heat to form calcium oxide (also known as quicklime) and carbon dioxide gas. The carbon dioxide gas is what causes the fuming or bubbling that you may see coming from the kettle. The calcium oxide also forms a white or grayish powdery substance, known as scale or limescale, which can build up in the kettle and on heating elements over time. This can reduce the efficiency of the kettle and may even cause it to fail over time. Therefore, it is important to descale your kettle regularly if you live in an area with hard water.
Question 13 Report
A fixed mass of gas has a volume of 92cm3 at 3 oC. When will be its volume at 18 oC if the pressure remains constant
Answer Details
The volume of a fixed mass of gas at constant pressure is directly proportional to its temperature, according to Charles's Law. Therefore, we can use the formula V1/T1 = V2/T2 to solve this problem, where V1 and T1 are the initial volume and temperature of the gas, respectively, and V2 and T2 are the final volume and temperature of the gas, respectively. We are given that the initial volume V1 is 92cm3 and the initial temperature T1 is 3 oC, which we need to convert to the absolute temperature scale (Kelvin). To do this, we simply add 273 to the Celsius temperature to get T1 = 276 K. We are also given that the pressure remains constant, which means that the gas is isobaric. Therefore, we can use the formula V1/T1 = V2/T2 to find the final volume V2. Rearranging the formula, we get: V2 = (V1/T1) x T2 Substituting the values we have, we get: V2 = (92/276) x (18+273) V2 = (1/3) x 291 V2 = 97.0 cm3 Therefore, the volume of the gas at 18 oC will be 97.0 cm3.
Question 14 Report
When a salt loses its water of crystallization to the atmosphere on exposure, the process is said to be
Answer Details
The correct term is "Efflorescence". Efflorescence is a process where a salt loses its water of crystallization to the atmosphere, causing the salt crystals to dissolve and eventually evaporate, leaving behind a white powdery residue on the surface. This can happen due to changes in temperature, humidity, or air movement. Some examples of salts that can effloresce include sodium carbonate, calcium sulfate, and magnesium chloride. It's important to note that efflorescence is different from the other three options you listed: - Deliquescence refers to a substance that absorbs moisture from the air until it dissolves in the absorbed water. - Effervescence is the release of gas (typically carbon dioxide) from a substance, often in the form of bubbles. - Fluorescence is the property of certain substances to emit light (typically in the ultraviolet or visible spectrum) after absorbing light or other electromagnetic radiation.
Question 15 Report
In the electrolysis of brine, the anode is
Answer Details
The anode in the electrolysis of brine is typically made of carbon. During the electrolysis of brine (a solution of sodium chloride), positively charged sodium ions move towards the negatively charged anode, where they receive electrons and are converted into neutral sodium atoms. At the same time, negatively charged chloride ions move towards the positively charged cathode, where they lose electrons and are converted into chlorine gas. The anode material needs to be able to withstand the corrosive environment of the brine and not react with the sodium ions or chlorine gas produced during the electrolysis. Carbon is a commonly used material for the anode because it is stable in this type of environment.
Question 16 Report
All these are electromagnetic waves except
Answer Details
A photon is not an electromagnetic wave. Electromagnetic waves are a type of wave that consists of oscillating electric and magnetic fields, which propagate through space and can carry energy and information. Examples of electromagnetic waves include white light, X-rays, and infrared radiation. A photon, on the other hand, is a quantum of energy that carries electromagnetic force. Photons are the basic building blocks of electromagnetic waves and are responsible for the transfer of electromagnetic energy. Photons can also be thought of as particles of light, as they exhibit both wave-like and particle-like behavior.
Question 17 Report
Calculate the relative molecular mass of Limestone CaCO3, (Ca = 40, C =12, O = 16)
Answer Details
To calculate the relative molecular mass of limestone (CaCO3), we need to add up the atomic masses of each element in the molecule. The formula for limestone (CaCO3) tells us that there is one calcium atom (Ca), one carbon atom (C), and three oxygen atoms (O) in each molecule. The atomic masses of these elements are: - Calcium (Ca) = 40 - Carbon (C) = 12 - Oxygen (O) = 16 To find the relative molecular mass of limestone, we can add up the atomic masses of each element: Relative molecular mass = (atomic mass of Ca) + (atomic mass of C) + 3 x (atomic mass of O) Relative molecular mass = (40) + (12) + 3 x (16) Relative molecular mass = 40 + 12 + 48 Relative molecular mass = 100 Therefore, the relative molecular mass of limestone (CaCO3) is 100. This means that one molecule of limestone has a mass of 100 atomic mass units (amu), which is the standard unit for measuring the mass of atoms and molecules.
Question 18 Report
If glucose is heated with concentration tetraoxosulphate (VI) acid, it will be dehydrated to
Answer Details
Question 19 Report
When steam is passed over red-hot carbon, the substances produced are
Answer Details
When steam is passed over red-hot carbon, the substances produced are hydrogen and carbon (II) oxide. The reaction that occurs is known as the water-gas shift reaction and is represented by the chemical equation: C(s) + H2O(g) → CO(g) + H2(g) In this reaction, steam (H2O) reacts with carbon (C) in the presence of heat to produce carbon (II) oxide (CO) and hydrogen gas (H2). The carbon (II) oxide is formed because the carbon combines with only one of the oxygen atoms from the steam to form CO, while the other oxygen atom combines with hydrogen to form water (H2O). Therefore, the substances produced by passing steam over red-hot carbon are hydrogen gas and carbon (II) oxide.
Question 20 Report
Detergents are manufactured with straight hydrocarbon chains so as to make them
Answer Details
Question 21 Report
A compound contains 40.0% carbon 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180, find the molecular formula.
[H = 1, C = 12, O = 16]
Answer Details
First, we need to determine the empirical formula of the compound, which gives the simplest whole-number ratio of atoms in the compound. To do this, we assume that we have 100 g of the compound, which means we have 40.0 g of carbon, 6.7 g of hydrogen, and 53.3 g of oxygen. Next, we convert these masses to moles by dividing by the respective atomic or molecular masses: - Carbon: 40.0 g / 12.0 g/mol = 3.33 mol - Hydrogen: 6.7 g / 1.0 g/mol = 6.7 mol - Oxygen: 53.3 g / 16.0 g/mol = 3.33 mol The mole ratio of these elements is approximately 1:2:1, which gives us the empirical formula CH2O. To find the molecular formula, we need to know the molecular mass of the empirical formula. The molecular mass of CH2O is: - Carbon: 1 x 12.0 g/mol = 12.0 g/mol - Hydrogen: 2 x 1.0 g/mol = 2.0 g/mol - Oxygen: 1 x 16.0 g/mol = 16.0 g/mol Total: 30.0 g/mol We are given that the molar mass of the compound is 180 g/mol. To find the molecular formula, we divide the molar mass by the empirical formula mass: 180 g/mol ÷ 30.0 g/mol = 6 The molecular formula is the empirical formula multiplied by the whole number 6: 6 x CH2O = C6H12O6. Therefore, the molecular formula of the compound is C6H12O6.
Question 22 Report
There are basic particles from which matter called be made except
Answer Details
Of the options given, the basic particle that cannot be used to make matter is salt. Salt is a compound made up of two or more different elements (sodium and chlorine) that are chemically combined in a fixed ratio. Therefore, salt cannot be considered a basic particle of matter, as it is composed of multiple atoms bonded together. On the other hand, atoms, ions, and molecules are considered to be the basic particles of matter. Atoms are the smallest units of an element that retain the chemical properties of that element. Ions are atoms or groups of atoms that have an electric charge due to a gain or loss of electrons. Molecules are groups of two or more atoms held together by chemical bonds. In summary, while salt is not a basic particle of matter, atoms, ions, and molecules are considered to be the fundamental building blocks of all matter.
Question 23 Report
The leachate of a certain plant ash is used in local soap making because it contains
Answer Details
Question 24 Report
Two equal bulbs, one containing ammonia and the other nitrogen are opened mouth-to-mouth to each other at room temperature. The entropy in the mixture of gases is likely to
Answer Details
When two equal bulbs, one containing ammonia and the other nitrogen, are opened mouth-to-mouth to each other at room temperature, the entropy of the mixture of gases is likely to increase. Entropy is a measure of the disorder or randomness in a system. When the two gases are allowed to mix, they will spontaneously spread out to fill the entire space of the bulbs. This process of mixing increases the disorder of the system, and hence, the entropy increases. Ammonia and nitrogen are both gases at room temperature and they mix together easily because they are both nonpolar molecules. As a result, the entropy of the system will increase as the two gases mix together. Therefore, the correct answer is increase.
Question 25 Report
Electronic configuration of an elements 13x in the subsidiary energy level is
Answer Details
The electronic configuration of an element 13x in the subsidiary energy level is 1s22s22p63s23p1. The electronic configuration of an element describes the way electrons are arranged in the energy levels or shells around the nucleus. The first energy level can hold up to 2 electrons, the second energy level can hold up to 8 electrons, and the third energy level can hold up to 18 electrons. For element 13x, we can determine its electronic configuration by using the periodic table. Element 13x is in group 13, which means it has 3 valence electrons. The valence electrons are the outermost electrons that are involved in chemical reactions. The electronic configuration of element 13x in the ground state, which means it is not excited, is 1s22s22p63s23p1. This means that the first energy level is full with 2 electrons (1s2), the second energy level is also full with 8 electrons (2s22p6), and there is 1 electron in the third energy level (3s23p1). This electron is a valence electron and is involved in chemical bonding. The other options listed do not have the correct number of electrons in the valence shell, and therefore are not the correct electronic configuration for element 13x.
Question 26 Report
One note of a hydrocarbon 36g of carbon and its density is 20. The structure of hydrocarbon is (organic chemical)
Answer Details
2VD = Rmm
VD = Vapour Density, Rmm = relative
2 × 20 − 40 molecular mass
Mole of carbon − 36/12
= 3
Mole of H2 = 40 − 36
= 4
The compound contains 3mole of carbon and 4 hydroge
Question 27 Report
A difference between chemical and physical change is that in a chemical change
Answer Details
The main difference between a chemical change and a physical change is that in a chemical change, a new substance is formed. During a chemical change, the atoms or molecules of the original substance rearrange themselves to form a new substance with different properties. In contrast, a physical change involves a change in the physical state or appearance of a substance, but the chemical composition of the substance remains the same. For example, melting ice is a physical change because the solid water (ice) is converted into liquid water, but the chemical composition of the water remains the same. Therefore, the correct answer to the question is that in a chemical change, a new substance is formed. The other options may be associated with chemical changes as well, but they are not defining characteristics of chemical changes.
Question 28 Report
Which of the following metals burn with brick red flame?
Answer Details
Calcium (Ca) burns with a brick red flame. When a metal burns, it reacts with oxygen in the air to form a metal oxide. The color of the flame depends on the energy released during the reaction, which can vary depending on the metal. Calcium has a relatively low ionization energy, meaning it requires less energy to remove an electron from its outermost shell compared to other metals such as lead (Pb), sodium (Na), and magnesium (Mg). When calcium reacts with oxygen in the air, it releases a relatively large amount of energy, resulting in a bright, brick red flame. In contrast, lead, sodium, and magnesium have higher ionization energies, meaning they require more energy to remove an electron from their outermost shells. As a result, their reactions with oxygen release less energy and produce flames of different colors. In summary, calcium burns with a brick red flame because it has a relatively low ionization energy and releases a large amount of energy when it reacts with oxygen in the air.
Question 29 Report
N2O4(g) ↔ 2NO2(g)
In the endothermic reaction above, more product formation will be favoured by
Answer Details
In the endothermic reaction N2O4(g) ↔ 2NO2(g), more product formation will be favored by a decrease in pressure. This is because the reaction produces two moles of gas for every one mole of N2O4 that reacts. According to Le Chatelier's Principle, when the pressure on a system is decreased, the equilibrium will shift to the side of the reaction with more moles of gas to compensate for the decrease in pressure. In this case, the equilibrium will shift to the side of the reaction that produces more gas molecules, which is the side with more NO2(g) molecules. Therefore, a decrease in pressure will favor the formation of more NO2(g) molecules, resulting in more product formation.
Question 30 Report
An element used in the production of matches is
Answer Details
An element used in the production of matches is sulphur. Sulphur is a chemical element that is commonly found in nature, and it is used in the production of matches because of its flammable properties. The striking surface of a matchbox contains a mixture of sulphur and other chemicals. When the match is struck against the surface, the friction generates heat, which ignites the sulphur and other chemicals. This produces a flame that can light the matchstick, which is made of wood and coated with a mixture of chemicals that also include sulphur. Sulphur is a highly reactive element, which makes it an ideal choice for use in matches. It is also a non-metal, which means it has some unique properties, such as being a good insulator of electricity. However, sulphur is also a toxic substance, and its use in matches has been regulated in some countries to reduce the risk of health and environmental hazards.
Question 31 Report
NH3(g) + HCl(s) → NH4Cl(s)
The entropy change in the system above is
Question 33 Report
P1V1 = P2V2 supports ?
Answer Details
The formula P1V1 = P2V2 represents Boyle's law. It states that the pressure and volume of a gas are inversely proportional to each other, at a constant temperature. This means that as the pressure on a gas increases, its volume decreases, and vice versa, as long as the temperature remains constant. Conversely, if the pressure decreases, the volume increases. For example, imagine you have a balloon that is filled with a fixed amount of gas. If you were to squeeze the balloon, you are increasing the pressure on the gas inside, and the volume of the balloon would decrease in response. Conversely, if you were to release the pressure by letting go of the balloon, the volume of the balloon would increase as the pressure on the gas inside decreases. Therefore, if you know the initial pressure and volume of a gas, and the pressure is changed while keeping the temperature constant, you can use Boyle's law to calculate the new volume of the gas.
Question 34 Report
In countries where the temperature falls below 273K, salt is always sprinkled on the icy road in order to
Answer Details
Salt is sprinkled on icy roads in cold countries to lower the melting point of the ice. When salt is spread on the ice, it dissolves and creates a brine solution with a lower freezing point than pure water. This means that the ice will start to melt even when the temperature is below its normal freezing point, making the road safer for vehicles and pedestrians to use. In other words, the salt helps prevent the road from becoming too slippery and dangerous by melting the ice at lower temperatures.
Question 35 Report
What volume of 0.5 MH2SO4 will exactly neutralize 20cm3 of 0.1 MNaOH Solution?
Question 36 Report
In the electrolysis of CuSO4(g) using platinum electrodes, the reaction at the anode is
Answer Details
Question 37 Report
What is the volume of energy required to burn 45cm3 of mixture at S.T.P
Answer Details
CH4(g) + 2O2(g) → 2H2O(g)
1 volume of methane will react with 90cm3 of oxygen at S.T.P
Question 38 Report
Chlorine gas turns a damp starch-iodide paper
Answer Details
Chlorine gas turns a damp starch-iodide paper from its original colour to a dark blue color. The reason behind this change is that chlorine gas reacts with the iodide ions in the paper, oxidizing them to iodine. This iodine then reacts with the starch in the paper, forming a dark blue complex known as starch-iodine complex. Therefore, the presence of chlorine gas can be detected by observing the change in color of the damp starch-iodide paper from its original color to a dark blue color.
Question 40 Report
The major source of oxides of nitrogen is from the burning of
Answer Details
The major source of oxides of nitrogen (NOx) is from the burning of fuel, such as gasoline and diesel, in internal combustion engines like those found in cars, trucks, and airplanes. When fuel is burned, it reacts with the air to produce heat and power. However, this reaction also produces NOx, which can contribute to air pollution and have negative impacts on human health and the environment.
Question 41 Report
the elements that belong to the third period of the periodic table are
Answer Details
Question 42 Report
The above orbital diagram shown the electronic configuration of
Answer Details
The above orbital diagram shows the electronic configuration of nitrogen. An orbital diagram is a way of representing the arrangement of electrons in an atom using boxes to represent orbitals and arrows to represent electrons. In this diagram, there are two boxes representing the first energy level (closest to the nucleus) and three boxes representing the second energy level. The boxes are labeled with the appropriate sublevel (s, p, d, or f) and the number of electrons in each sublevel is shown with arrows pointing up or down. Nitrogen has seven electrons, which are distributed among the sublevels according to the aufbau principle and Hund's rule. The first two electrons occupy the 1s sublevel, while the remaining five electrons occupy the 2s and 2p sublevels. The 2s sublevel can hold up to two electrons, which are shown in the first box of the second energy level. The 2p sublevel can hold up to six electrons, but in this case, only three of the four available boxes are filled with one electron each, leaving one box empty. Overall, the electronic configuration of nitrogen is 1s2 2s2 2p3, meaning it has two electrons in the 1s sublevel, two electrons in the 2s sublevel, and three electrons in the 2p sublevel.
Question 43 Report
According to the kinetic theory, an increase in temperature causes the kinetic energy of particles to
Answer Details
According to the kinetic theory, an increase in temperature causes the kinetic energy of particles to increase. All matter is made up of tiny particles called atoms and molecules that are constantly in motion. The kinetic energy of these particles is related to their temperature, which is a measure of the average kinetic energy of all the particles in a substance. When you increase the temperature of a substance, you add energy to the particles, causing them to move faster and collide with each other more frequently and with greater force. This increase in collisions and energy results in an overall increase in the kinetic energy of the particles. Therefore, an increase in temperature leads to an increase in the kinetic energy of the particles, while a decrease in temperature leads to a decrease in the kinetic energy of the particles.
Question 44 Report
Alloys are best prepared by
Answer Details
Alloys are best prepared by cooling a molten mixture of the metals. This is because when metals are melted, they become more reactive and are able to mix and combine evenly. By combining different metals in a molten state, they can form a new material with unique properties that are different from the original metals. This process of cooling the molten mixture of metals is called solidification, which allows the metals to solidify into a homogeneous mixture, forming an alloy. This method is widely used in industry and can be used to create alloys with precise compositions and properties for specific applications. Electroplating involves coating a metal with a thin layer of another metal, which is different from forming an alloy. Arc-welding, on the other hand, is used to join metals together, but it doesn't create a new material with different properties. Reducing and mixing metallic oxides is another method used to form alloys, but it is less common and more complicated than the process of melting and cooling a mixture of metals.
Question 45 Report
Which of the following compounds can be represented by the molecular formula C2H6O?
Answer Details
Ethanol can be represented by the molecular formula C2H6O. The molecular formula of a compound gives you the number of atoms of each element that are present in one molecule of the compound. In this case, the molecular formula C2H6O tells us that there are two carbon atoms, six hydrogen atoms, and one oxygen atom in one molecule of the compound. Ethanol is a common alcohol that is used in many products, including alcoholic beverages, fuel, and solvents. Its molecular formula is C2H6O, which matches the formula given in the question. Propane (not Propanel) has the molecular formula C3H8, methanoic acid has the molecular formula HCOOH, and glucose has the molecular formula C6H12O6. Therefore, the only compound among the options that matches the molecular formula C2H6O is ethanol.
Question 46 Report
Chlorine, consisting of two isotopes of mass numbers 35 and 37, has an atomic mass of 35.5.
The relative abundance of the isotope of mass number 37 is?
Answer Details
Question 47 Report
The acid used in electrolysis of water is dilute
Answer Details
None of the given options are commonly used as the acid in the electrolysis of water. In fact, the most common acid used in the electrolysis of water is dilute sulfuric acid (H2SO4). The purpose of the acid in the electrolysis of water is to increase the conductivity of the water. Pure water is a poor conductor of electricity, but by adding a small amount of acid, it can become a better conductor. This is because the acid dissociates into ions in the water, which allows the electrical current to pass more easily through the solution. However, it's important to note that the acid used in the electrolysis of water is typically only slightly acidic or "dilute." This is because too much acid can cause unwanted side reactions and can also corrode the electrodes used in the process. Therefore, the acid is usually added in a small amount to achieve the desired conductivity without causing any harm to the equipment or the process itself.
Question 48 Report
In the production of soap, concentrated sodium chloride solution is added to
Answer Details
In the production of soap, concentrated sodium chloride solution is added to decrease the solubility of the soap. Soap is typically made by the saponification reaction between a fat or oil and a strong base, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH). This reaction produces soap molecules, which have both hydrophilic (water-loving) and hydrophobic (water-repelling) ends. During the soap-making process, the soap molecules can remain dissolved in the water layer and not separate out into the soap layer due to their hydrophilic ends, which prefer to interact with water molecules. By adding a concentrated sodium chloride (NaCl) solution, the solubility of the soap molecules in water is decreased due to the formation of ion-dipole interactions between the sodium and chloride ions and the hydrophilic ends of the soap molecules. As a result, the soap molecules are forced to separate out into the soap layer, making them easier to extract and purify. Therefore, the addition of concentrated sodium chloride solution in soap production decreases the solubility of the soap.
Question 49 Report
5 block elements of the periodic table one made up of
Answer Details
5 block elements only are made up of group 1 and 2 options A,C,D takes place of the other blocks in the periodic table p,d,f etc.
Question 50 Report
Cathode rays causes an object placed behind a perforated anode to cast a shadow on the screen. This observation shows that the rays
Answer Details
The observation of a shadow cast by an object placed behind a perforated anode when cathode rays are passed through it shows that the rays travel in straight lines. This is because only the areas not blocked by the object can be illuminated on the screen. Therefore, options A, B, and C are incorrect, as none of them are related to the observed phenomenon.
