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Question 3 Report
Which of the following species has the largest ionic radius
Answer Details
Among the given species, Ca\(^{2+}\) has the largest ionic radius. Ionic radius is defined as half the distance between the nuclei of two adjacent ions of the same element in a crystal lattice. The ionic radius increases as we move down a group in the periodic table and decreases as we move across a period. Ca\(^{2+}\) has the largest ionic radius among the given species because it has the least nuclear charge compared to the other ions. As we move from left to right in a period, the number of protons in the nucleus increases, resulting in a greater nuclear charge. The greater nuclear charge attracts the electrons more strongly, causing the ionic radius to decrease. In contrast, as we move down a group, the number of electron shells increases, leading to an increase in the size of the ion. Therefore, among the given species, Ca\(^{2+}\) has the largest ionic radius because it has more electron shells and the least nuclear charge, while S\(^{2-}\) has the smallest ionic radius because it has the greatest nuclear charge and the least electron shells.
Question 4 Report
What number of moles of oxygen would exert a pressure of 10 atm at 320 K in an 8.2 dm\(^{2}\) cylinder?
[R = 0.082 atm dm\(^{3}\) mol\(^{-1}\) K\(^{-1}\)]
Question 5 Report
The Bohr model of the atom proposed the existence of
Answer Details
The question is asking about the Bohr model of the atom and what it proposed. The Bohr model of the atom was proposed by Niels Bohr in 1913. It is a model that describes the structure of the atom, with the nucleus at the center and electrons orbiting the nucleus in specific energy levels or shells. Therefore, the answer to the question is "electron shells". The Bohr model proposed the existence of electron shells, which are specific energy levels that electrons occupy around the nucleus of an atom. These shells are quantized, meaning that they can only have certain energy values, and electrons can move between them by absorbing or releasing energy. Option A, "the nucleus", is not specific to the Bohr model and was already known to exist before the development of the Bohr model. Option C, "nucleons", refers to the collective term for the particles in the nucleus (protons and neutrons), which are not part of the Bohr model's description of the electron shells. Option D, "neutrons", is a type of nucleon, but again, it is not part of the Bohr model's description of the electron shells.
Question 6 Report
Which of the following oxide causes acid rain?
Answer Details
The oxide that causes acid rain is NO\(_{2}\). Acid rain is a type of rain that has a low pH value (below 5.6) due to the presence of certain pollutants in the air. These pollutants, such as sulfur dioxide and nitrogen oxides, can react with water in the atmosphere to form acids that fall to the ground as acid rain. Among the options given, NO\(_{2}\) is the only oxide that contains nitrogen, which is a major contributor to acid rain. When NO\(_{2}\) is released into the atmosphere, it reacts with water to form nitric acid, which is a strong acid that can lower the pH of rainwater. Therefore, the correct answer is option D: NO\(_{2}\).
Question 7 Report
The 25°C evaporation of a 100 cm\(^{3}\) solution of K\(_{2}\)CO\(_{3}\) to dryness gave 14g of the salt. What is the solubility of K\(_{2}\)CO\(_{3}\) at 25°25C? [K\(_{2}\)CO\(_{3}\) = 138]
Answer Details
Question 8 Report
Consider the structure below
How many carbon atoms does the parent chain contain?
Answer Details
The parent chain in the given structure contains 5 carbon atoms. The parent chain is the longest continuous chain of carbon atoms in a molecule, and it is used as the basis for naming organic compounds. In the given structure, the longest continuous chain of carbon atoms starts from the leftmost carbon atom and extends to the rightmost carbon atom, with a total of 5 carbon atoms. The other carbon atoms in the molecule are attached to the parent chain as substituents. In this case, there are two substituents, each consisting of a single carbon atom with a methyl (-CH3) group attached. Therefore, the parent chain in the given structure contains 5 carbon atoms.
Question 9 Report
Which of the following scientists discovered the electrons?
Answer Details
Joseph J. Thomson discovered electrons. Joseph J. Thomson was a British physicist who conducted a series of experiments in the late 19th century to study the nature of electric discharge in gases. In 1897, he performed a famous experiment involving cathode rays, which are beams of electrons that travel from the negatively charged electrode (cathode) to the positively charged electrode (anode) in a vacuum tube. Thomson observed that cathode rays could be deflected by magnetic and electric fields, indicating that they were negatively charged particles. He proposed that these particles were a fundamental component of all atoms and called them "corpuscles," which later became known as electrons. Thomson's discovery of the electron revolutionized our understanding of atomic structure and led to the development of modern physics. He was awarded the Nobel Prize in Physics in 1906 for his work on the conduction of electricity in gases. Therefore, Joseph J. Thomson discovered electrons.
Question 10 Report
The isotopes of neon are represented by the symbols \(^{20}\)\(_{x}\) Ne, \(^{21}\) \(_{y}\) Ne, and \(^{22}\) \(_{z}\) Ne. The relationship between x, y, and z is?
Answer Details
Question 11 Report
Which of the following pairs of molecules form hydrogen bonds?
Answer Details
The pair of molecules that form hydrogen bonds are C\(_{2}\)H\(_{5}\)OH and CH\(_{3}\)OH. A hydrogen bond is a type of chemical bond that forms between a partially positively charged hydrogen atom and a partially negatively charged atom, such as oxygen or nitrogen. In the case of C\(_{2}\)H\(_{5}\)OH and CH\(_{3}\)OH, both molecules contain oxygen atoms, which have a partial negative charge. Additionally, the hydrogen atoms in these molecules are partially positively charged. This creates an opportunity for hydrogen bonding to occur between the oxygen atom in one molecule and the hydrogen atom in another molecule. In contrast, the other pairs of molecules listed do not contain the necessary atoms with partial charges for hydrogen bonding to occur. CH\(_{3}\)OH and H\(_{2}\) do not have any partially charged atoms, while H\(_{2}\)S and CH\(_{4}\) do not contain atoms with the necessary partial charges to form hydrogen bonds. NH\(_{3}\) and SO\(_{2}\) have partially charged atoms, but these atoms do not interact with each other in a way that allows for hydrogen bonding to occur. Therefore, only C\(_{2}\)H\(_{5}\)OH and CH\(_{3}\)OH can form hydrogen bonds.
Question 12 Report
A molecular of phosphorus is
Answer Details
A molecule is a group of two or more atoms held together by chemical bonds. A monoatomic molecule is a molecule made up of a single atom. Phosphorus, which has the chemical symbol P and atomic number 15, can exist in several allotropes, including white, red, and black phosphorus. At standard temperature and pressure, white phosphorus is the most stable allotrope and exists as P\(_{4}\) molecules, which are tetraatomic. Therefore, the correct answer is tetraatomic.
Question 13 Report
Potassium trioxonitrate (V) can be obtained from its solution by----------
Question 14 Report
Which of the following half reaction equations represent the reaction at the cathode
Answer Details
In an electrochemical cell, the cathode is the electrode where reduction occurs. Reduction is the gain of electrons by a species. So, the half-reaction equation that involves the gain of electrons is the reaction at the cathode. Option B represents the reaction at the cathode because it involves the gain of two electrons, which is a reduction half-reaction. The species B\(^{2+}\) is being reduced to B\(_{(s)}\), which means that B\(^{2+}\) is gaining two electrons to become a neutral atom of B. Option A is not the reaction at the cathode because it involves the oxidation of A\(_{(s)}\) to A\(^{3+}\). This is an oxidation half-reaction, and it occurs at the anode. Option C is not the reaction at the cathode because it involves the reduction of A\(^{3+}\) to A\(_{(s)}\). This is a reduction half-reaction, but it occurs at the anode in an electrolytic cell. Option D is not the reaction at the cathode because it involves the oxidation of B\(_{(s)}\) to B\(^{2+}\). This is an oxidation half-reaction, and it occurs at the anode. In summary, option B represents the reaction at the cathode because it involves the gain of two electrons, which is a reduction half-reaction.
Question 15 Report
The formation of ethene from dehydration of ethanol can be described as-------
Answer Details
The dehydration of ethanol to form ethene is a chemical reaction in which water is removed from ethanol, resulting in the formation of ethene. The reaction can be represented as: CH\(_{3}\)CH\(_{2}\)OH → CH\(_{2}\)=CH\(_{2}\) + H\(_{2}\)O This reaction involves the elimination of a molecule of water (H\(_{2}\)O) from ethanol (CH\(_{3}\)CH\(_{2}\)OH) to form ethene (CH\(_{2}\)=CH\(_{2}\)). Such reactions are known as elimination reactions. In elimination reactions, a molecule is removed from a reactant, resulting in the formation of a new product. This is different from addition reactions, in which two or more reactants combine to form a single product, and substitution reactions, in which one atom or group is replaced by another. Therefore, the correct answer is (B) an elimination reaction.
Question 16 Report
What is the empirical formula of a hydrocarbon containing 0.160 moles of carbon and 0.640 moles of hydrogen
Answer Details
To determine the empirical formula of a hydrocarbon, we need to know the number of moles of each element present in the compound. In this case, we are given that the hydrocarbon contains 0.160 moles of carbon and 0.640 moles of hydrogen. To find the empirical formula, we need to determine the simplest whole-number ratio of the atoms in the compound. We can start by dividing the number of moles of each element by the smallest number of moles to obtain a ratio of the atoms in the compound. In this case, the smallest number of moles is 0.160, which corresponds to the number of moles of carbon. Dividing the number of moles of hydrogen by 0.160, we get: 0.640 mol H / 0.160 mol C = 4 mol H/mol C This means that there are four times as many hydrogen atoms as carbon atoms in the compound. Therefore, the empirical formula of the hydrocarbon is CH\(_{4}\), which corresponds to one carbon atom and four hydrogen atoms. So, the answer is option (C) CH\(_{4}\).
Question 17 Report
The following ions have the same electron configuration except
\(_{8}\)O, \(_{12}\)Mg, \(_{13}\)AI, \(_{17}\)CI
Answer Details
Question 18 Report
An element, Q, contains 69% of\(^{63}\)Q and 31% of \(^{65}\)Q. What is the relative atomic mass of Q?
Answer Details
The relative atomic mass (RAM) of an element is the weighted average of the masses of all its isotopes, taking into account their abundance. In this case, we are given the percentage abundance of two isotopes of element Q, and we can use this information to calculate its RAM. To calculate the RAM of Q, we need to multiply the atomic mass of each isotope by its percentage abundance (as a decimal), and then add these values together. The formula for calculating the RAM is: RAM = (mass\(_{63}\)Q x % abundance of\(^{63}\)Q) + (mass\(_{65}\)Q x % abundance of\(^{65}\)Q) The atomic mass of\(^{63}\)Q is 63, and the atomic mass of\(^{65}\)Q is 65. Substituting the given values into the formula, we get: RAM = (63 x 0.69) + (65 x 0.31) RAM = 43.47 + 20.15 RAM = 63.62 Therefore, the relative atomic mass of element Q is 63.62. So, the answer is option (B) 63.6.
Question 19 Report
The most common method of preparing insoluble salts is by
Answer Details
The most common method of preparing insoluble salts is by double decomposition. Double decomposition is a chemical reaction that involves the exchange of ions between two ionic compounds. In this reaction, the cations and anions of two different compounds switch places, resulting in the formation of two new compounds. When one of the products of this reaction is an insoluble salt, it can be separated from the solution by filtration. For example, suppose we want to prepare the insoluble salt lead(II) chloride (PbCl\(_2\)). We can do this by reacting lead(II) nitrate (Pb(NO\(_3\))\(_2\)) with sodium chloride (NaCl): Pb(NO\(_3\))\(_2\) + 2 NaCl → PbCl\(_2\) + 2 NaNO\(_3\) In this reaction, the lead(II) cation (Pb\(^{2+}\)) and the chloride anion (Cl\(^-\)) switch places, resulting in the formation of lead(II) chloride and sodium nitrate (NaNO\(_3\)), which remains soluble in water. The lead(II) chloride is insoluble in water and will precipitate out of the solution. We can then isolate the solid PbCl\(_2\) by filtration. Therefore, double decomposition is the most common method of preparing insoluble salts, as it allows us to precisely control the reaction conditions and obtain the desired product with high purity.
Question 20 Report
Elements with high ionization energies would-------
Answer Details
Elements with high ionization energies would have high effective nuclear charges. This means that the positively charged nucleus of the atom has a strong hold on its electrons, making it difficult to remove them. The ionization energy is the energy required to remove an electron from an atom. Elements with high ionization energies are therefore less likely to lose electrons easily and become positively charged ions. This can also result in elements having higher electronegativities, which is a measure of an atom's tendency to attract electrons towards it.
Question 21 Report
What is the concentration of a solution which contains 0.28g of potassium hydroxide in 100 cm\(^{3}\) of solution [KOH = 56]
Answer Details
To calculate the concentration of a solution, we need to know the amount of solute and the volume of the solution. The given amount of potassium hydroxide is 0.28 g and the volume of the solution is 100 cm\(^{3}\) or 0.1 dm\(^{3}\). First, we need to calculate the number of moles of potassium hydroxide in the solution by dividing its mass by its molar mass: Number of moles of KOH = Mass of KOH / Molar mass of KOH = 0.28 g / 56 g/mol = 0.005 mol Then, we can calculate the concentration of the solution in mol dm\(^{-3}\) by dividing the number of moles by the volume of the solution in dm\(^{3}\): Concentration of KOH solution = Number of moles / Volume of solution = 0.005 mol / 0.1 dm\(^{3}\) = 0.05 mol dm\(^{-3}\) Therefore, the concentration of the solution is 0.05 mol dm\(^{-3}\). is the correct answer.
Question 22 Report
The reactivity of fluorine is high because of
Answer Details
The reactivity of fluorine is high due to its high electronegativity. Electronegativity is the ability of an atom to attract electrons towards itself. Fluorine has the highest electronegativity of all elements, which means that it attracts electrons towards itself more strongly than any other element. This makes fluorine highly reactive, as it tends to form strong bonds with other atoms by either gaining or sharing electrons. In addition to its high electronegativity, the small size of the fluorine atom also contributes to its high reactivity. The small size allows fluorine atoms to approach other atoms very closely, which enhances the strength of the interactions between them. The availability of d-orbitals and the strong F-F bond are not responsible for the high reactivity of fluorine. Therefore, the correct answer is option A: its high electronegativity.
Question 23 Report
How many coulombs of electricity would liberate 1.08g of Ag from a solution of silver salt?
[Ag = 108.0; 1F = 96500 C]
Answer Details
To calculate the number of coulombs of electricity required to liberate 1.08g of Ag from a silver salt solution, we need to use Faraday's laws of electrolysis, which state that the amount of a substance produced by electrolysis is directly proportional to the quantity of electricity passed through the electrolyte. The formula for calculating the amount of electricity required to liberate a certain amount of a substance is: Quantity of electricity = (Mass of substance / Equivalent weight) × 96500 The equivalent weight of Ag is equal to its atomic weight divided by its valency. Since the valency of Ag is 1, the equivalent weight is equal to its atomic weight, which is 108.0 g/mol. Using the above formula, we get: Quantity of electricity = (1.08 g / 108.0 g/mol) × 96500 C/mol Quantity of electricity = 965 C Therefore, the number of coulombs of electricity required to liberate 1.08g of Ag from a silver salt solution is 965 C. In summary, option C is the correct answer.
Question 24 Report
How many molecules of oxygen would occupy a volume of 2.24 cm\(^{3}\) at s.t.p?
[Molar volume at s.t.p = 22,400 cm\(^{3}\), Avogadro's number = 6.02 x 10\(^{23}\)]
Question 25 Report
The ratio of carbon atoms of hydrogen atoms in a hydrocarbon is 1:2. If its molecular mass is 56, what is its molecular formula?
Answer Details
In order to determine the molecular formula of the hydrocarbon, we need to use the information given in the question to calculate the number of carbon and hydrogen atoms in the molecule. The ratio of carbon atoms to hydrogen atoms in the hydrocarbon is 1:2, which means that for every one carbon atom, there are two hydrogen atoms. We can represent this ratio using the general formula C\(_{n}\)H\(_{2n}\), where n is the number of carbon atoms in the molecule. Next, we are given the molecular mass of the hydrocarbon, which is 56. To find the value of n, we need to use the molecular formula to calculate the molecular mass. For the general formula C\(_{n}\)H\(_{2n}\), the molecular mass can be calculated using the formula: Molecular mass = n x (atomic mass of carbon) + 2n x (atomic mass of hydrogen) Substituting the values of atomic mass for carbon and hydrogen (12 and 1, respectively), and the given molecular mass of 56, we get: 56 = n x 12 + 2n x 1 Simplifying this equation, we get: 56 = 14n n = 4 Therefore, the molecular formula of the hydrocarbon is C\(_{4}\)H\(_{8}\), which is option B in the question. In summary, the hydrocarbon in the question has a ratio of carbon atoms to hydrogen atoms of 1:2, and a molecular mass of 56. Using this information, we can calculate that its molecular formula is C\(_{4}\)H\(_{8}\).
Question 26 Report
Study the graphs below and use them to answer the question below
Which of the graphs illustrates the variation of the solubility of a salt in water (y-axis), with an increase in temperature (x-axis) if the dissolution process is exothermic?
Question 27 Report
When CuSO\(_{4(aq)}\) is added to Pb(NO\(_{3}\))\(_{2(aq)}\)--------
Answer Details
Question 28 Report
Study the graphs below and use them to answer the question below
Which of the graphs illustrates the variation of the pH of a given volume of strong acid solution (y-axis) with the volume of strong base titrated against its (x-axis)?
Answer Details
Question 29 Report
The basic property of salts used as drying agents is by?
Answer Details
The property of salts that makes them effective drying agents is their ability to absorb moisture from their surroundings, a characteristic called hygroscopy. When exposed to an environment with high humidity, the salt molecules attract and hold onto water molecules, effectively removing moisture from the surrounding area. This makes them useful for drying out materials such as solvents or wet surfaces. Salts with high solubility, low melting point, or efflorescence are not typically effective as drying agents because they tend to absorb water and dissolve rather than removing it from the environment. Salts with low solubility, on the other hand, tend to be more effective drying agents as they can absorb more moisture without dissolving.
Question 30 Report
The activation energy of the reaction is
Question 31 Report
Study the graphs below and use them to answer the question below
Which of the following illustrates the variation of the rate of evolution of gas from a given length of magnesium ribbon (y-axis) with an increase in the concentration of the added (x-axis)?
Question 32 Report
Which of the following gasses is highly soluble in water at room temperature
Answer Details
The solubility of a gas in water is determined by several factors, including temperature, pressure, and the nature of the gas and the solvent. At room temperature, the gas that is highly soluble in water is ammonia (NH\(_{3}\)). Ammonia is a polar molecule, meaning it has regions of positive and negative charge, and it readily dissolves in water due to the strong hydrogen bonding interactions between the ammonia molecule and the water molecules. In contrast, carbon (IV) oxide (CO\(_{2}\)) is only slightly soluble in water, and it is often used as a reference for measuring the solubility of other gases. Chlorine (Cl\(_{2}\)) is highly reactive and toxic, and it is not very soluble in water at room temperature. Nitrogen (N\(_{2}\)) is an unreactive gas and is only slightly soluble in water. So, of the gases listed, ammonia is the most soluble in water at room temperature.
Question 33 Report
Protons and electrons are called fundamental particles because they----------
Answer Details
Protons and electrons are called fundamental particles because they are considered to be the building blocks of matter. They cannot be divided into smaller particles and still retain their unique properties. Additionally, protons have a positive charge and electrons have a negative charge, which makes them essential for creating stable atoms. Finally, protons and electrons are found in all matter, meaning that they are fundamental to the composition of the universe. Therefore, all of the given options are correct, and each contributes to the overall understanding of why protons and electrons are fundamental particles.
Question 34 Report
Which of the following pairs of compounds would form a precipitate when their aqueous solutions are mixed?