WAEC SSCE - Chemistry - 2009

When protein is heated to a high temperature it undergoes

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When proteins are heated to high temperatures, they undergo denaturation. Denaturation is the process by which a protein loses its three-dimensional structure, which is critical to its function. This change in structure is due to the breaking of the weak bonds holding the protein together, such as hydrogen bonds, ionic bonds, and hydrophobic interactions. The loss of these bonds causes the protein to unfold and lose its specific shape, which can lead to a loss of function. Denaturation can also be caused by other factors such as changes in pH, exposure to detergents or solvents, or high pressure.

The separation of petroleum fractions depends on the differences in their

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The separation of petroleum fractions is based on their boiling points. The different fractions of petroleum are separated by a process called fractional distillation, where crude oil is heated and vaporized. As the vapor rises through a column, it gradually cools down. As it cools, the vapor condenses into a liquid, and the different fractions with different boiling points condense at different levels in the column. The lighter fractions with lower boiling points, such as gases and liquids like gasoline, condense at the top of the column, while the heavier fractions with higher boiling points, such as liquids like diesel and lubricating oil, condense at lower levels. Thus, the separation of petroleum fractions is dependent on the differences in their boiling points.

Which of the following statement is correct? The solubility of

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Consider the reaction represented by the equation: ²³⁸₉₂U + ¹₀ → ¹³⁹ ₅₆Ba + ⁹⁴ ₃₆Kr + 3¹ ₀n. The reaction represents a

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The reaction shown in the equation ²³⁸₉₂U + ¹₀ → ¹³⁹ ₅₆Ba + ⁹⁴ ₃₆Kr + 3¹ ₀n represents nuclear fission. Nuclear fission is a process in which a heavy nucleus is split into two or more smaller nuclei and typically releases a large amount of energy in the form of heat and radiation. In this particular reaction, uranium-238 is bombarded with a neutron, which causes it to split into two smaller nuclei (barium-139 and krypton-94) and three neutrons. This process also releases a significant amount of energy in the form of radiation.

A solution that contains as much solute as it can dissolve at a given temperature is said to be

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A solution that contains as much solute as it can dissolve at a given temperature is said to be saturated. This means that no more solute can be dissolved in the solution without changing the temperature or pressure. Any additional solute added to a saturated solution will remain undissolved and settle at the bottom of the container. The saturation point is determined by the solubility of the solute in the solvent, which is the maximum amount of solute that can dissolve in a given amount of solvent at a given temperature and pressure.

In a mixture of gases which do not react chemically together, the pressure exerted by the individual gases is called

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Which of the following hydroxides will readily dissolved in water?

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NaOH will readily dissolve in water. This is because it is a strong base and its ionic bonds with Na⁺ and OH^- are easily broken in the presence of water, allowing the ions to separate and become hydrated. In contrast, Cu(OH)₂, Pb(OH)₂, and Zn(OH)₂ are relatively insoluble in water, meaning that their ionic bonds are not easily broken and they do not readily dissociate into their constituent ions in water.

Which of the following acids from normal salt only?

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Which of the following scientists discovered the neutron?

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James Chadwick discovered the neutron. In the early 1930s, he conducted a series of experiments that led to the discovery of an uncharged subatomic particle within the nucleus of the atom. This particle was later identified as the neutron, which plays a critical role in nuclear reactions and the stability of the nucleus. Chadwick's discovery of the neutron earned him the Nobel Prize in Physics in 1935.

What is the value of -14^oC on the Kelvin temperature scale?

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The Kelvin temperature scale is an absolute temperature scale where 0 Kelvin represents the lowest possible temperature (absolute zero). The Kelvin temperature scale is related to the Celsius scale by adding 273.15 to the Celsius value. To convert -14°C to Kelvin, we need to add 273.15 to the value. Thus, -14°C + 273.15 = 259.15 K. Therefore, the value of -14°C on the Kelvin temperature scale is 259 K (option a).

What is the percentage by weight of calcium in Ca(OCI)₂? [Ca = 40, Cl = 35.5, O = 16]

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Which of the following oxides of nitrogen has oxidation number of + 1?

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The product of the reaction between C ₂H₅OH and concentrated H₂SO ₄ at 170^oC is

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Which of the following ions is isoelectronic with neon? [₃Li, _{3F, 10Ne, 17CI,19K]}

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The question is asking which of the given ions has the same electronic configuration as neon. Neon is a noble gas and has an electronic configuration of 1s²2s²2p⁶. Isoelectronic refers to ions or atoms that have the same number of electrons, thus the same electronic configuration. Among the given options, the ion that has the same number of electrons as neon is the one that has 10 electrons in total. Looking at the options, the only ion with 10 electrons is F^-. Therefore, F^- is isoelectronic with neon. Therefore, the correct option is F^-.

Dry hydrogen chloride when dissolved in methylbenzene

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Dry hydrogen chloride gas (HCl) when dissolved in methylbenzene does not affect litmus paper. This is because methylbenzene is a non-polar solvent and does not contain water, which is required for litmus paper to change color. Therefore, litmus paper cannot be used to test the acidity or basicity of the solution.

If 100 atoms of element X contains 70 atoms of ⁹X and 30 atoms of ¹¹X, calculate the relative atomic mass of X

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To calculate the relative atomic mass of X, we need to take into account the mass and abundance of each isotope of X. We know that element X has two isotopes: ⁹X and ¹¹X. To calculate the relative atomic mass of X, we can use the formula: Relative atomic mass of X = (mass of ⁹X x % abundance of ⁹X) + (mass of ¹¹X x % abundance of ¹¹X) / 100 Substituting the values we have, we get: Relative atomic mass of X = (9 x 70) + (11 x 30) / 100 Relative atomic mass of X = 630 + 330 / 100 Relative atomic mass of X = 9.6 Therefore, the relative atomic mass of X is 9.6.

What is the product of the reaction between propene and 1 mole of hydrogen iodide?

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The reaction between propene and 1 mole of hydrogen iodide results in the addition of the hydrogen iodide molecule to the carbon-carbon double bond in propene. The hydrogen atom adds to one carbon atom of the double bond, and the iodine atom adds to the other carbon atom. As a result, the product formed is CH ₃CHICH₃, which is 2-iodopropane. Therefore, the correct answer is: the product of the reaction between propene and 1 mole of hydrogen iodide is CH₃CHICH₃.

Consider the reaction represented by the following equation: H _2(g) + \(\frac{1}{2}\) O_(g) → H ₂O_(g) ∆H =-285.8 KJmo ^-1 ∆H represents the enthalpy of

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∆H represents the enthalpy change of a chemical reaction, which is defined as the difference between the enthalpy of the products and the enthalpy of the reactants. In this case, the equation given is the reaction of hydrogen gas and oxygen gas to form water, so ∆H represents the enthalpy change of the formation of water. Therefore, the correct answer is "formation".

Which of the following expressions correctly represents Charles' law?

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Which of the following electronic configurations correctly represents an element in period 3 of the periodic table?

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Period 3 of the periodic table includes the elements sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), and chlorine (Cl). The correct electronic configuration for an element in period 3 should have 3 energy levels and electrons distributed among those energy levels according to the Aufbau principle. Looking at the options given: - represents an element in period 2 as it has only 2 energy levels. - represents the noble gas configuration of the element neon (Ne) in period 2. - represents an element in period 3 with 3 energy levels, where the outermost energy level has 6 electrons (3s² 3p⁴). This configuration is consistent with the element sulfur (S). - represents an element in period 4 as it has 4 energy levels. Therefore, the correct option representing an element in period 3 is with the electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁴.

Which of the following factors will affect the rate of the reaction represented by the equation? 2HCI_(aq) + CaCO _3(s) → CaCI_2(aq) + H₂O _(I) + CO_2(g) l. Pressure ll. Concentration III. Nature of reactants IV. Temperature

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The rate of the reaction represented by the equation 2HCI(aq) + CaCO3(s) → CaCI2(aq) + H2O(I) + CO2(g) can be affected by various factors: - Pressure: Pressure affects the rate of a reaction only if there are gases involved in the reaction. In this reaction, CO2 is produced as a gas, so increasing the pressure will increase the rate of the reaction. - Concentration: Increasing the concentration of the reactants will increase the number of collisions between the reactant particles and thus increase the rate of the reaction. - Nature of reactants: The nature of the reactants can affect the rate of the reaction. For example, a reaction involving reactive metals like magnesium will proceed faster than a reaction involving less reactive metals like copper. - Temperature: Increasing the temperature will increase the kinetic energy of the particles, resulting in more collisions and thus increasing the rate of the reaction. Therefore, the factors that will affect the rate of this particular reaction are ll, lll, and IV.

Ethanol reacts with excess acidified K₂Cr ₂O₇ to produce

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Ethanol reacts with excess acidified K₂Cr ₂O₇ to produce ethanoic acid. This reaction is an oxidation reaction, where ethanol is oxidized to ethanoic acid. The K₂Cr ₂O₇ acts as an oxidizing agent and converts the ethanol to ethanoic acid by removing hydrogen atoms from ethanol and adding oxygen atoms to form a carboxylic acid. The other options listed in the question are not produced in this reaction.

How many molecules are there in 14 g of nitrogen at s.t.p.? [N = 14, Avogadro's constant = 6.02 x 10²³ mol^-1]

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Which of the following elements has the electronic configuration:1s²2s²2p⁶3s²3p¹? [₁₁Na, ₁₃A1,
₁₄N,₁₆S]

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Which of the following raw materials is used in the plastic industry ?

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Ethene is the raw material used in the plastic industry. Ethene, also known as ethylene, is a hydrocarbon with the formula C2H4. It is produced from the cracking of petroleum fractions or natural gas. Ethene is a monomer that can be polymerized to form polyethylene, which is a versatile plastic used in a wide range of applications, from packaging materials to toys and medical devices. Calcium, hydrogen, and methane are not typically used as raw materials in the plastic industry.

A consequence of global warming is

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A consequence of global warming is flooding. Global warming causes the temperature of the earth to rise, leading to the melting of glaciers and ice caps, which increases the volume of water in the oceans. This increase in water level leads to flooding in low-lying areas and coastal regions. Additionally, global warming can cause more intense and frequent weather events, such as hurricanes and heavy rainfall, which can also lead to flooding.

What is the molecular formula of a compound with empirical CH₂O and vapour density of 90? [H = 1, C = 12, O = 16]

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In bonded atoms, increase in electronegativity difference,

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In bonded atoms, the electronegativity difference determines the distribution of electrons between the atoms. When there is an increase in the electronegativity difference between two atoms in a bond, one atom attracts electrons more strongly than the other, resulting in an uneven distribution of electrons. This uneven distribution of electrons leads to an increase in the polarity of the bond, as the atom that attracts electrons more strongly gains a partial negative charge, while the other atom gains a partial positive charge. Therefore, an increase in electronegativity difference increases the polarity of the bond.

Which of the following compounds is not a double salt?

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A double salt is a combination of two different salts which crystallize together to form a single substance with a unique formula. The formula of a double salt is a combination of the formulas of the two salts that make it up. From the given options, the compound that is not a double salt is Zn(OH)NO₃. This is because it does not contain two different salts that have crystallized together to form a new substance. Rather, it is a single compound containing the elements zinc, oxygen, nitrogen, and hydrogen. Therefore, the answer is: Zn(OH)NO₃

How many orbitals are associated with the p-sub energy level?

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The p-sub energy level has a total of three orbitals. These orbitals are represented as Px, Py, and Pz. Each orbital can hold a maximum of two electrons, and together they can hold a total of six electrons. Therefore, the correct answer is 3.

Which of the following molecules is not linear in shape?

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NH₃ is not linear in shape. It has a trigonal pyramidal shape because of the presence of one lone pair of electrons on the nitrogen atom. The other three bonded hydrogen atoms are at an angle of approximately 107 degrees to each other. CO₂, O₂, and HCl are all linear in shape.

The major product in the solvay process is

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The Solvay process is a method of producing sodium carbonate (Na₂CO₃) from brine and ammonia (NH₃). The process involves reacting brine with ammonia to form ammonium chloride (NH₄Cl), which is then reacted with limestone (CaCO₃) to produce carbon dioxide (CO₂), water (H₂O), calcium chloride (CaCl₂), and ammonia. The carbon dioxide is then reacted with the remaining ammonia to produce ammonium bicarbonate (NH₄HCO₃), which is then heated to produce sodium carbonate (Na₂CO₃), water, and carbon dioxide. Thus, the major product in the Solvay process is Na₂CO₃.

The electron configuration of carbon atom in its excited state is [ ₆C]

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The electron configuration of carbon in its ground state is 1s²2s²2p². This means that there are two electrons in the 1s orbital, two in the 2s orbital, and two in the 2p orbital. However, the question is asking about the excited state of carbon, which means that at least one electron has been promoted from a lower energy level to a higher energy level. In the case of carbon, one of the electrons in the 2s orbital is promoted to the 2p orbital, resulting in the electron configuration [ ₆C] 1s²2s¹2p³. Therefore, the correct answer is 1s²2s¹2px¹2py¹2pz¹.

An important medical use of nuclear radiations is

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One important medical use of nuclear radiations is radiotherapy. Radiotherapy uses high-energy radiation to destroy cancer cells and shrink tumors. This type of treatment is usually delivered by a machine called a linear accelerator, which produces high-energy X-rays or gamma rays that are directed towards the tumor. The radiation damages the DNA of the cancer cells, causing them to die. Radiotherapy is often used in combination with other treatments such as chemotherapy and surgery, and can be effective in treating a range of cancers including lung, breast, prostate, and brain cancer.

Which of the following salts is insoluble in water?

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The correct answer is AgCI. AgCI is insoluble in water because it is a sparingly soluble salt. When AgCI is added to water, it does not dissolve readily and forms a cloudy mixture. The cloudiness is due to the formation of small insoluble particles of AgCI in water. This is because the attractive forces between Ag+ ions and CI- ions in AgCI are stronger than the attractive forces between these ions and water molecules. In contrast, Pb(NO3)2, Na2CO3, and AgNO3 are soluble salts that dissolve readily in water to form clear solutions.

Consider the reaction represented by the equation: 2H₂SO _4(aq0 + C_(s) → 2H₂O_(l) + 2SO_2(g) + CO _2(g) H₂SO ₄ is acting as

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The following properties are characteristics of transition elements except

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The question is asking which of the given properties is NOT a characteristic of transition elements. Transition elements are a group of elements in the periodic table that have partially filled d orbitals. They have several unique properties, including the ability to form complex ions, form coloured compounds, and exhibit catalytic abilities. However, one property that is not typically associated with transition elements is fixed oxidation states. Unlike many other elements, transition elements can have multiple oxidation states and are not limited to one fixed state. Therefore, the correct answer to the question is "fixed oxidation states."

Which of the following arrangements is in order of increasing ionization energy?

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A catalyst increases the rate of chemical reaction by

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A catalyst is a substance that increases the rate of a chemical reaction by providing an alternative reaction pathway with lower activation energy. Activation energy is the energy required to start a chemical reaction. By lowering the activation energy, a catalyst makes it easier for reactant molecules to react and form products. As a result, the reaction can occur more quickly, which increases the rate of the chemical reaction. Therefore, the correct option is "decreasing the activation energy of the reaction".

An element Q forms a compound QCI₅. In which group of the periodic table is Q?

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The Roman numeral in the compound QCI₅ indicates the oxidation state of element Q in the compound, which is 5. From this information, we can determine the group number of element Q in the periodic table. Group number of an element is equal to its highest oxidation state. Since the oxidation state of element Q in the compound is 5, it belongs to group V of the periodic table. Therefore, the correct answer is V.

Which of the following properties of covalent compounds is not correct? They

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The correct option is "have high boiling points." Covalent compounds are formed by sharing of electrons between two non-metal atoms. These compounds generally have low melting and boiling points due to their weak intermolecular forces. They are mostly gaseous or volatile liquids. Covalent compounds also do not dissociate into ions in solution, and therefore they are non-electrolytes. However, some covalent compounds with strong intermolecular forces may have high boiling points.

Which of the following alloys does not contain copper? l. Brass II. Bronze III. Steel

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Steel does not contain copper, so the correct answer is III only. Brass is an alloy of copper and zinc, and bronze is an alloy of copper and tin. Steel is an alloy of iron and carbon, and may also contain other elements such as manganese, nickel, and chromium.

The electron configuration of carbon atom in its excited state is [ 6C]

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The electron configuration of an atom describes the arrangement of electrons in its energy levels or orbitals. The notation [ 6C ] means that the excited carbon atom has six electrons in its outermost energy level, which is the second energy level (n=2). The correct electron configuration for a carbon atom in its excited state is 1s²2s¹2p². The notation [ 6C ] can be understood as follows: the normal electron configuration for carbon is 1s²2s²2p², meaning that it has four electrons in its outermost energy level. By exciting one of the 2s electrons to the empty 2p orbital, the atom now has a total of six electrons in the n=2 energy level, hence the notation [ 6C ]. Option D, 1s²2s¹2px¹2py¹2pz¹, represents the electron configuration of a carbon atom in its ground state.

Consider the reaction represented by the equation: 2NaHCO₃ → Na₂CO ₃ + H ₂O + CO ₂. What is the mass of sodium trioxocarbonate (lV) produced by the complete decomposition of 33.6 g of sodium hydrogen trioxocarbonate (IV)? [NaHCO₃ = 84, Na₂CO₃ = 106]

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The balanced equation for the reaction shows that 2 moles of NaHCO₃ produce 1 mole of Na₂CO₃, and the molar mass of NaHCO₃ is 84 g/mol. Therefore, 84 g of NaHCO₃ will produce 106 g of Na₂CO₃. To determine the mass of Na₂CO₃ produced from 33.6 g of NaHCO₃, we need to use stoichiometry. 33.6 g NaHCO₃ x (1 mol NaHCO₃ / 84 g NaHCO₃) x (1 mol Na₂CO₃ / 2 mol NaHCO₃) x (106 g Na₂CO₃ / 1 mol Na₂CO₃) = 21.2 g Na₂CO₃ Therefore, the mass of sodium trioxocarbonate (lV) produced by the complete decomposition of 33.6 g of sodium hydrogen trioxocarbonate (IV) is 21.2 g. The correct answer is 21.2 g.

Which of the following substances is the anode in the dry Leclanche cell ?

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In a dry Leclanche cell, the anode is the negative electrode that releases electrons into the external circuit during the cell's discharge. The anode of a dry Leclanche cell is the zinc container. It acts as the negative terminal of the cell and is where the oxidation of zinc metal to zinc ions takes place, producing electrons and zinc ions which move towards the cathode. Therefore, the correct option is zinc container.

Which of the following elements exhibits the same chemical properties as the atom \(\frac{35}{17}\)X? An element with

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The element with the symbol \(\frac{35}{17}\)X represents an atom of chlorine with 17 protons and 18 neutrons. Elements with the same number of protons have the same chemical properties. Therefore, the answer is (a) an element with atomic number 17, which is chlorine.

How many protons does ⁴⁰20Ca contain?

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The atomic number of an element is defined as the number of protons in the nucleus of its atom. In the symbol ⁴⁰20_Ca, 20 is written as a subscript, which represents the atomic number of calcium. Therefore, the number of protons in the nucleus of ⁴⁰20_Ca is 20. Answer: 20.

Salts that contain water of crystallization are said to be

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Salts that contain water of crystallization are said to be hydrated. Water of crystallization is the water molecules that are tightly bound to the salt molecules in a crystal structure. These water molecules can be removed by heating or by exposing the salt to dry air. When the water is removed, the salt becomes anhydrous. The number of water molecules present in a hydrated salt is indicated by a dot followed by a number in the chemical formula. For example, CuSO4.5H2O is copper sulfate pentahydrate, which means it contains five molecules of water of crystallization.

In a chemical reaction, ∆H is positive when

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Which of the statements about the behaviour of the atom is correct?

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The correct statement about the behavior of the atom is that cations are smaller than the parent atom. When an atom loses one or more electrons to form a cation, the number of electrons is less than the number of protons, resulting in a net positive charge. This positive charge attracts the remaining electrons more strongly towards the nucleus, causing the atomic radius to decrease. Therefore, cations are smaller than their parent atoms. Conversely, when an atom gains one or more electrons to form an anion, the negative charge causes the electron cloud to expand, resulting in a larger atomic radius than the parent atom. Hence, the other options are incorrect.

Which of the following noble gases has electronic structure similar to that of N in NH ₃? [\(\frac{14}{7}\)N]

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The number of particles in one mole of a chemical compound is the

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The number of particles in one mole of a chemical compound is called Avogadro's number. Avogadro's number is a constant that represents the number of particles (such as atoms, molecules, or ions) in one mole of a substance, which is approximately 6.02 x 10^23 particles. This number is used to convert between the number of moles of a substance and the number of particles it contains. For example, one mole of water contains 6.02 x 10^23 water molecules. Therefore, Avogadro's number is the correct option.

Which of the following dilute acids does not react with metals to liberate hydrogen?

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(a) (i) State Boyle's law.

(ii) Give the mathematical expression of Boyle's law.

(iii) Sketch the graphical representation of Boyle's law.

(b) A given mass of gas occupied 500 cm3 at 30°C and 6.5 x 104 Nm\(^{-2}\). Calculate the volume of the gas at s.t.p. [ Standard pressure = 1.01 x 105 Nm\(^{-2}\)]

(c) Explain why an inflated balloon expands in warm water.

(d)(i) What is meant by the term vapour density? (ii) Determine the vapour density of SO\(_{2}\). [ S = 32, O = 16 ]

(e)(i) Which of the following gases, SO\(_{2}\) and NH\(_{3}\) can be collected by I. upward delivery; II. downward delivery?

(ii) What would be the nature of the solution formed by dissolving each of the following substances in water separately. I. SO\(_{2}\) II. NH\(_{3}\)

(iii) State the property exhibited by SO\(_{2}\) and NH\(_{3}\) in the following equations:

I. 2H\(_{2}\)S\(_{(aq)}\) + SO\(_{2(g)}\) \(\to\)  3S\(_{(s)}\) + 2H\(_{2}\)O\(_{(/)}\)

II. 3CuO\(_{(s)}\) + 2NH\(_{3(g)}\)  \(\to\) 3Cu\(_{(s)}\) + 3H\(_{2}\)O\(_{(/)}\) + N\(_{2(s)}\).

(f) State two alloys of tin.

(ii) Give one use of each of the alloys in (f)(i).

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None

TEST OF PRACTICAL KNOWLEDGE QUESTION

(a) List three pieces of apparatus required for the evaporation of sodium chloride solution to dryness.

(b)(i) List two normal salts which when dissolved in water turn red litmus blue.

(ii) State the phenomenon that is responsible for the action on the litmus in (b)(i).

(c) State what would be observed on adding BaCl\(_2\) solution to a portion of a saturated Na\(_2\)CO\(_3\), followed by dilute HCI in excess.

(i) A gas Q decolourized acidified KMnO\(_4\) solution. Suggest what Q could be.

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None

(a) Atoms of four non-metallic elements in the same group of the periodic table are arranged in order of increasing atomic radius as R < T < W < X. Which of the elements

(i) would readily lose electron(s) from the outermost shell;

(ii) is most electronegative;

(iii) would T displace from aqueous solution;

(iv) is at the top of the group?

(b) The following table shows the electronic configuration of two elements Y and Z.

(i) Name the I. group to which Y belongs II. period to which Z belongs.

(ii) What is the number of protons present in an atom of Z?

(iii) How many unpaired electrons are in an atom of Y?

(iv) Write the formula of the compound formed between Y and Z

(c) Name the type of bond(s) that exist(s) in each of the following compounds.

(i) CaCl\(_2\); (ii) NH\(_4\)Cl; CCl\(_4\)

(d) Describe how the conductance of a molar solution of ammonia compares to that of sodium hydroxide solution.

(e) State the type of reaction illustrated by each of the following equations:

(i) CH\(_3\)CH\(_2\)OH\(_{(/)}\) + CH\(_3\)COOH\(_{(aq)}\) \(\rightleftharpoons\) CH\(_3\)COOC\(_2\)H\(_5\)\(_{(/)}\) + H\(_2\)O\(_{(/)}\)

(ii) H+\(_{Y^+_{(aq)}\) + OH\(^+_{(aq)}\) \(\to\) H\(_2\)O

(f) Determine the volume of the residual gas when 20.0cm\(^3\) of hydrogen was sparked with 15.0cm\(^3\) of oxygen and the resulting mixture cooled to room temperature.

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 (a)(1) Define each of the following terms: I. deliquescence; II. efflorescence.

(ii) Give one example I substance that undergoes each of the processes in (a)(i).

(b) Outline how three colourless gases suspected to be ethane, ethene and ethyne could be distinguished in the laboratory.

(c)(i) What is water crystallization?

(ii) Hydrated calcium chloride (CaCl\(_2\) = 111, xH\(_2\)O) contains 49.32% water of cystallization. Calm the value of x. [ (CaCl\(_2\) = 111, H\(_2\)O = 18 ]

(d) Name one calcium compound used (i) in the manufactur cement; (ii) as a dessicant; (iii) in the production of plaster of Paris (POP);

(iv) to neutralise acidic soils

(e) A concentrated solution of sodium chloride was electrolysed using graphite electrodes.

(i) State the ions present in the solution

(ii) Name the products at the I. anode, II. cathode.

(iii) Give the by-product of the electrolysis.

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None

TEST OF PRACTICAL KNOWLEDGE QUESTION

Burette readings (initial and final reading) must be given to two decimal places. Volume of pipette used must also be recorded but no account of experimental procedure is required. All calculations must be done in your answer book.

A is 0.0950 mol dm\(^{-3}\) HCI. B is a solution 13.50g dm\(^{-3}\) of X\(_2\)CO\(_3\).10H\(_2\)O.

(a) Put A into the burette and titrate it against 20.0 cm\(^3\) or 25.0 cm\(^3\) portions öf B using methyl orange as an indicator. Tabulate your readings and calculate the average volume of A used.

(b) From your results and the information provided above, calculate the;

(i) concentration of B in mol dm\(^{-3}\);

(ii) molar mass of X\(_2\)CO\(_3\).10H\(_2\)O in g mol\(^{-1}\);

(iii) percentage by mass X in X\(_2\)C)\(_3\).10H\(_2\)O. [H = 1, C = 12, O = 16]. The equation for the reaction involved in the titration is 2HCl\(_{(aq)}\) + X\(_2\)CO\(_3\).10H\(_2\)O\(_{(aq)}\) \(\to\) 2XCl\(_{(aq)}\) + 11H\(_2\)O\(_{(l)}\) + CO\(_{2(g)}\)  

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None

(a)(i) Outline a suitable procedure for the preparation of ZnCl\(_2\) crystals stating from zinc granules.

(ii) Write a balanced equation for the reaction in (a)(i).

(b) Considei' the following solutions: Na\(_2\)SO\(_{4(aq)}\), CH3COOK\(_{(aq)}\), Pb(NO\(_3\))\(_{2(aq)}\) and MgCl\(_2\). Which of them has/have a pH

(i) greater than 7;

(ii) equal to 7;

(iii) less than 7?

(c)(i) Determine the oxidation number of Mn in I. MnO\(_2\); II. KMnO\(_4\).

(ii) State one laboratory use of each of the .compounds in (c)(i).

(d) Explain why oxidation and reduction processes are complementary.

(e) Consider the reaction represented by the equation: Fe\(_{(s)}\) + 2Ag\(^+_{(aq)}\) \(\to\) Fe\(^{2+}_{(aq)}\) + 2Ag\(_{(s)}\)

(i) Write a balanced ionic half equations for the reaction.

(ii) Which of the species is I. oxidized; II. reduced?

(iii) State the change in the oxidation number of silver during the reaction.

Détails de la réponse

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