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Question 1 Report
| GAS | CO2 | N2 | O2 |
| % BY VOLUME | 4 | 72 | 24 |
The above table shows the compositions of the atmosphere of planet X. Which of these gases are present in higher percentages on earth?
Answer Details
Question 2 Report
30 cm3 of oxygen at 10 atmosphere pressure is placed in a 20 dm3 container. Calculate the new pressure if the temperature is kept constant.
Answer Details
Given:
First, convert all volumes to the same units. Since 1 dm3dm3 is 1000 cm3cm3:
𝑉2=20 dm3=20×1000 cm3=20000 cm3V2=20dm3=20×1000cm3=20000cm3
Now, using Boyle's Law:
𝑃1𝑉1=𝑃2𝑉2P1V1=P2V2
Substitute the known values into the equation:
10×30=𝑃2×2000010×30=P2×20000
300=𝑃2×20000300=P2×20000
Solve for 𝑃2P2:
𝑃2=30020000P2=20000300
𝑃2=0.015 atmospheresP2=0.015atmospheres
Therefore, the new pressure if the temperature is kept constant is:
Question 3 Report
The following non-metal form acidic oxides with oxygen except?
Answer Details
An acidic oxide is an oxide that reacts with water to form an acidic solution. Non-metals have a greater tendency to form acidic oxides than metals. Therefore, among the given options, the non-metal that does not form an acidic oxide with oxygen would be the one that does not react with water to form an acidic solution. Out of the given options, chlorine is the non-metal that does not form acidic oxides with oxygen. Chlorine reacts with oxygen to form a number of oxides such as chlorine monoxide (Cl2O), chlorine dioxide (ClO2), and chlorine trioxide (ClO3), but none of these oxides react with water to form an acidic solution. Instead, they react with water to form oxyacids or oxoacids such as hypochlorous acid (HClO), chlorous acid (HClO2), and chloric acid (HClO3), which are stronger acids than the oxides. Therefore, the correct answer is chlorine.
Question 5 Report
Hard water is water with high concentrations of dissolved ions, in particular calcium and
Answer Details
Hard water is water that contains high amounts of dissolved minerals, specifically calcium and magnesium ions. These minerals come from the rocks and soil that the water flows through and can accumulate in the water as it travels to your home. When you use hard water, it can leave mineral deposits on your pipes, fixtures, and appliances, which can reduce their efficiency and lifespan. It can also make soap less effective and leave your skin feeling dry and itchy. Therefore, it is important to treat hard water if it is a problem in your area.
Question 6 Report
A piece of radioactive element has initially 8.0×10^22 atoms. The half life of two days after 16 days the number of atom is
Question 7 Report
H+ + OH− → H2 O
The equation above illustrates
Question 8 Report
A certain liquid has a high boiling point. It is viscous, non-toxic, and miscible with water to be hygroscopic; this liquid most likely to be
Answer Details
The liquid is most likely to be option number 4: CH3OHCHOH2OH, which is also known as glycerol or glycerin. Glycerol has a high boiling point of 290°C, which is much higher than the boiling points of the other options. It is also a viscous liquid, which means it is thick and sticky. Glycerol is non-toxic, and it is often used in food, pharmaceuticals, and cosmetics. Furthermore, glycerol is miscible with water, which means that it can be easily mixed with water to form a homogeneous solution. It is also hygroscopic, which means that it can absorb water from the air. These properties make glycerol a useful substance in many applications, such as as a moisturizer in skincare products or as a humectant in food processing.
Question 9 Report
Crude petroleum is converted to useful products by the process of?
Answer Details
The process of converting crude petroleum into useful products is known as fractional distillation. Crude petroleum is a mixture of different hydrocarbons, and fractional distillation separates these hydrocarbons based on their boiling points. During the process of fractional distillation, crude petroleum is heated to a high temperature, and the resulting vapors are passed through a tower called a fractionating column. This column contains a series of trays, and each tray contains a specific temperature range. As the vapors rise up the column, they cool and condense into liquids on the tray with a temperature that matches their boiling point. The liquids are then collected and further refined into useful products like gasoline, diesel, jet fuel, and heating oil. Fractional distillation is an important process because it allows us to separate and purify the different components of crude petroleum, which have different properties and uses. For example, gasoline has a lower boiling point and is more volatile than diesel fuel, which makes it ideal for use in cars. By separating these components, we can create products that meet specific needs and requirements.
Question 10 Report
N2 O4 ? 2NO2 (? = -ve)
From the reaction above, which of these conditions would produce the highest equilibrium yield for N2 O4 ?
Answer Details
The highest equilibrium yield of N2O4 would be produced at low temperature and low pressure. In a chemical reaction, the position of the equilibrium can be influenced by changing the temperature or pressure. A decrease in temperature or an increase in pressure favors the side of the reaction with the fewer moles of gas (in this case, N2O4). This means that, if the temperature is low and the pressure is low, there will be more N2O4 at equilibrium, as the reaction will shift to the right to counteract the reduction in the concentration of N2O4. So, low temperature and low pressure would produce the highest equilibrium yield of N2O4.
Question 11 Report
How many neutrons are present in atom with mass number and atomic number 37 and 17 respectively?
Answer Details
The atomic number of an atom represents the number of protons in the nucleus of the atom. Since the atomic number given is 17, it means that there are 17 protons in the nucleus. The mass number of an atom represents the total number of protons and neutrons present in the nucleus. Therefore, if the mass number is given as 37, it means that the total number of protons and neutrons in the nucleus is 37. To determine the number of neutrons in the nucleus, we can subtract the atomic number (which represents the number of protons) from the mass number (which represents the total number of protons and neutrons). Thus, the number of neutrons in the atom with a mass number of 37 and an atomic number of 17 is: Number of neutrons = Mass number - Atomic number = 37 - 17 = 20 Therefore, the answer is 20.
Question 12 Report
The oxidation number of oxygen in BaO2 is
Answer Details
To determine the oxidation number of oxygen in BaO2, we can use the fact that the overall charge of a compound must be zero. Barium (Ba) is a Group 2 element and has an oxidation state of +2. The compound BaO2 has no net charge, so the sum of the oxidation states of all the atoms must be zero. Let x be the oxidation state of oxygen in BaO2. Therefore, we have: (+2) + 2(x) = 0 Solving for x, we get: x = -1 Therefore, the oxidation number of oxygen in BaO2 is -1.
Question 13 Report
What is the shape of a molecule of CCl4?
Answer Details
The shape of a molecule of CCl4 is tetrahedral.
Question 14 Report
Using the metal activity series, the metal that can liberate hydrogen gas from steam is?
Answer Details
The metal that can liberate hydrogen gas from steam is iron. The metal activity series is a list of metals in order of their reactivity, with the most reactive metals at the top and the least reactive metals at the bottom. When a metal is placed in a solution of steam (water vapor), the metal will react with the steam if it is more reactive than hydrogen. In this case, iron is more reactive than hydrogen, so it can displace hydrogen from the steam to form hydrogen gas. This reaction can be represented by the equation: Fe + H2O (steam) → FeO (iron oxide) + H2 (hydrogen gas) So, when steam is passed over iron, hydrogen gas is liberated and iron oxide is formed.
Question 15 Report
The dehydration of CH3 CH2 CH2 CH2 OH will give?
Question 16 Report
Which of the following will precipitate in dil. HCl
Answer Details
Among the given options, only CuS will precipitate in dilute HCl. CuS is insoluble in dilute HCl, and hence it will precipitate when added to dilute HCl. However, the other options will dissolve in dilute HCl, and hence they will not precipitate. ZnS will dissolve in dilute HCl to form ZnCl2 and H2S. Na2S will react with dilute HCl to produce H2S and NaCl. FeS will dissolve in dilute HCl to form FeCl2 and H2S. Therefore, the correct answer is (4) CuS.
Question 17 Report
A quantity of air passed through a weighted amount of alkaline pyrogallol. An increase in the weight of the pyrogallol would result from the absorption of
Answer Details
When air is passed through alkaline pyrogallol, the oxygen in the air is absorbed by the pyrogallol, resulting in an increase in the weight of the pyrogallol. The other gases in air, namely nitrogen, neon, and argon, do not react with pyrogallol under these conditions. Therefore, the answer is oxygen.
Question 18 Report
Which of the following is stable to heat
Answer Details
Out of the given options, K2CO3 is stable to heat.
Question 19 Report
Which of the following statement is TRUE of the complete hydrolysis of a glyceride by sodium hydroxide?
Answer Details
The statement that is TRUE of the complete hydrolysis of a glyceride by sodium hydroxide is: - 3 moles of NaOH are required for each mole of glyceride. During the hydrolysis of a glyceride (a triglyceride), the ester bonds between the fatty acid chains and glycerol are broken by the action of a strong base like sodium hydroxide. This results in the formation of glycerol and the corresponding salts of fatty acids, which are commonly known as "soaps." The reaction can be represented by the following equation: Triglyceride + 3 NaOH → 3 soap + glycerol As per the equation, 3 moles of NaOH are required to hydrolyze one mole of glyceride, and 3 moles of soap and one mole of glycerol are produced. The use of concentrated sulfuric acid (H2SO4) is not essential for the completion of the reaction, but it can be used as a catalyst to speed up the reaction.
Question 20 Report
A certain volume of gas at 298k is heated such that its volume and pressure are now four times the original values. What is the new temperature?
Answer Details
We can use the ideal gas law to solve this problem, which states that PV = nRT, where P is pressure, V is volume, n is the number of moles of gas, R is the gas constant, and T is temperature in kelvin. If the volume and pressure are both increased by a factor of 4, then the new volume V' and new pressure P' are given by: V' = 4V P' = 4P Substituting these values into the ideal gas law, we get: (4P)(4V) = nR(T') Simplifying this equation, we get: 16PV = nRT' Dividing both sides by PV, we get: 16 = nRT' / PV Since n, R, and P are constant, we can simplify this to: 16 = T' / T Solving for T', we get: T' = 16T Therefore, the new temperature is 16 times the original temperature. Substituting T = 298 K, we get: T' = 16 x 298 K = 4768 K So the correct answer is 4768.0K.
Question 21 Report
When marble is heated to 1473K, another whiter solid is obtained which reacts vigoriously with water to give an alkaline solution. The solution contains
Answer Details
The white solid obtained when marble (calcium carbonate, CaCO3) is heated to 1473K is calcium oxide (CaO), also known as quicklime. When quicklime reacts vigorously with water, it forms calcium hydroxide (Ca(OH)2), which is an alkaline solution. Therefore, the solution obtained from the reaction of quicklime with water contains calcium hydroxide (Ca(OH)2).
Question 22 Report
When heat is absorbed during a chemical reaction, the reaction is said to be
Answer Details
When heat is absorbed during a chemical reaction, the reaction is said to be endothermic. Endothermic reactions are characterized by the absorption of heat energy from the surroundings. In other words, the reactants absorb energy from the environment, usually in the form of heat, to form the products. As a result, the temperature of the surroundings decreases, and the reaction feels cold to the touch. Endothermic reactions can be found in many natural processes, such as photosynthesis, melting of ice, and the evaporation of liquids. These processes require energy to occur, and they absorb heat from the surroundings to power the reaction.
Question 23 Report
An organic compound which decolorizes bromine water is likely to be?
Answer Details
Question 24 Report
The boiling point of water, ethanol, toulene and butan-2-ol are 373.0k, 351.3k, 383.6k and 372.5k respectively, which liquid has the highest vapour pressure at 323.0k
Question 25 Report
Which of the following compound is NOT the correct formed compound when the parent metal is heated in air?
Answer Details
The compound that is NOT correctly formed when the parent metal is heated in air is: tri-iron tetraoxide (Fe2O). This is because the correct compound formed from the heating of iron in air is iron (III) oxide or Fe2O3. The formula for tri-iron tetraoxide is incorrect, as it implies that there are only three iron atoms in the compound when there should be four.
Question 26 Report
Electrons enter into orbitals in order of increasing energy as exemplified by?
Answer Details
Question 27 Report
Which of the following roles does sodium chloride play in preparation? It
Answer Details
The role that sodium chloride (NaCl) plays in soap preparation is to separate soap from glycerol. When fats or oils are hydrolyzed with an alkali, such as sodium hydroxide (NaOH), the result is a mixture of soap and glycerol. Adding NaCl to this mixture helps to induce the precipitation of the soap, allowing it to be separated from the glycerol. This process is known as "salting out" and is used to purify the soap and remove impurities. Sodium chloride does not react with glycerol or accelerate the decomposition of fat and oil. Also, it does not convert the fatty acid to its sodium salt as this conversion is done by the alkali (such as NaOH) during the saponification process.
Question 29 Report
In the extraction of iron, hot air is introduced into the blast furnace through?
Answer Details
In the extraction of iron, hot air is introduced into the blast furnace through tuyeres. Tuyeres are nozzles that are located at the bottom of the blast furnace, and they are used to blow hot air into the furnace. The hot air helps to burn the coke (a fuel made from coal) which provides the heat needed to melt the iron ore. The air also helps to remove the waste gases that are produced during the reaction, allowing the iron to be extracted more efficiently.
Question 30 Report
which of these compounds exhibits resonance
Answer Details
The compound that exhibits resonance is benzene.
Question 32 Report
Which of the following increases as boiling water changes to steam?
Answer Details
The degree of disorder of the system increases as boiling water changes to steam. When water is boiled and changes to steam, the water molecules gain energy and become more disordered, which means that the molecules move more rapidly and the entropy of the system increases. The temperature of the system also increases during this process, but the degree of disorder is the factor that specifically increases as the water changes to steam. The number of molecules and activation energy remain constant during this phase transition.
Question 33 Report
6g of Mg was to 100cm3 of 1 moldm3 H2 SO4 . What mass of Mg remained undissolved? (Mg = 24)
Answer Details
The balanced chemical equation for the reaction between magnesium (Mg) and sulfuric acid (H2SO4) is: Mg + H2SO4 -> MgSO4 + H2 According to the equation, one mole of Mg reacts with one mole of H2SO4 to produce one mole of magnesium sulfate (MgSO4) and one mole of hydrogen gas (H2). Since the concentration of the sulfuric acid is 1 moldm3, this means that there is one mole of H2SO4 in every 1 liter (1000 cm3) of solution. To determine the amount of Mg that reacts with the H2SO4, we need to use stoichiometry. One mole of Mg reacts with one mole of H2SO4, so the amount of Mg that reacts with 1 moldm3 of H2SO4 is given by: 6g / 24g/mol = 0.25 mol Since the reaction is 1:1, this means that 0.25 mol of H2SO4 is consumed in the reaction. The volume of the solution is 100cm3 (0.1 dm3), so the amount of H2SO4 in the solution is: 1 mol/dm3 x 0.1 dm3 = 0.1 mol The amount of H2SO4 that remains after the reaction is: 0.1 mol - 0.25 mol = -0.15 mol This negative value means that all of the H2SO4 was consumed in the reaction, and there is excess Mg left over. The mass of Mg that remains undissolved is given by: 0.15 mol x 24g/mol = 3.6g Therefore, the correct answer is 3.6g.
Question 34 Report
Addition of sodium chloride to water to form a solution would lead to?
Answer Details
The addition of sodium chloride to water to form a solution would lead to a decrease in freezing point and an increase in boiling point. This effect is known as colligative properties, which depend on the concentration of solute particles in a solution. When sodium chloride dissolves in water, it breaks down into sodium ions and chloride ions. These ions occupy space between water molecules and interfere with the formation of ice crystals during freezing. As a result, the freezing point of the solution is lowered below that of pure water. This is why we use salt to de-ice roads and sidewalks during the winter season. Similarly, the presence of solute particles in a solution also raises the boiling point of the solution. The increased concentration of solute particles in the solution causes a decrease in the vapor pressure of the solvent (water), making it harder for the solvent molecules to escape into the gas phase. This means that more energy is required to bring the solution to its boiling point compared to pure water. In summary, the addition of sodium chloride to water forms a solution with lower freezing point and higher boiling point compared to pure water.
Question 35 Report
H2SO4 is used to remove rust on the surface of iron (picking) before electroplating. The type of reaction involved is
Answer Details
The type of reaction involved when using H2SO4 to remove rust on the surface of iron is a redox reaction. This is because the sulfuric acid oxidizes the iron in the rust, converting it into iron(II) sulfate, while the acid itself is reduced to sulfur dioxide. The overall reaction can be written as follows: Fe2O3(s) + 3H2SO4(aq) → Fe2(SO4)3(aq) + 3H2O(l) In this reaction, the iron in Fe2O3 is oxidized from a +3 to a +2 oxidation state, while the sulfur in H2SO4 is reduced from a +6 to a +4 oxidation state. This transfer of electrons between the reactants is what defines a redox reaction.
Question 36 Report
An organic compound which liberate carbon(iv)oxide from trioxocarbonate(iv) solution is likely to be?
Answer Details
The organic compound that liberates carbon(iv)oxide from trioxocarbonate(iv) solution is CH3COOH (acetic acid). When acetic acid is added to a solution of trioxocarbonate(iv) (carbonate) it reacts to form carbon(iv)oxide gas, water and a salt. The balanced chemical equation for the reaction is: 2CH3COOH + Na2CO3 → CO2 + 2H2O + 2NaCH3COO The carbon(iv)oxide gas is released as bubbles, causing the solution to fizz. Therefore, CH3COOH is the organic compound that liberates carbon(iv)oxide from trioxocarbonate(iv) solution.
Question 37 Report
The sub-atomic particles located in the nucleus of an atom are?
Answer Details
The sub-atomic particles located in the nucleus of an atom are neutron and proton. The nucleus is the dense core of an atom that contains most of its mass. Protons are positively charged particles found in the nucleus, and they determine the atomic number of the element. Neutrons are neutral particles found in the nucleus, and they help stabilize the nucleus by balancing the repulsive forces between the positively charged protons. Electrons, on the other hand, are negatively charged particles that are located outside the nucleus in energy levels or shells. They are attracted to the positively charged nucleus by electrostatic forces and are involved in chemical bonding between atoms. The number of protons in the nucleus determines the identity of the element, while the number of neutrons determines its isotopes. Isotopes of an element have the same number of protons but different numbers of neutrons in the nucleus. In summary, the two sub-atomic particles located in the nucleus of an atom are neutron and proton.
Question 38 Report
The reactions below represent neutralization reaction, in which of them is the value of ΔH highest?
Answer Details
The reaction with the highest ΔH (change in enthalpy) would be the reaction between HCL and NaOH, which forms NaCL and H2O. This is because the formation of water releases energy in the form of heat, which is reflected in the positive ΔH value for this reaction. When an acid and a base react, they neutralize each other and form a salt and water, with the release of heat being a sign of an exothermic reaction.
Question 39 Report
What volume of (dm3 ) of water will be added to 10dm3 of 2.0 mol/dm3 HCL acid solution to give a final solution of 0.5 mol/dm3 ?
Answer Details
Question 40 Report
Which of the following is used as a moderator to control nuclear fission?
Answer Details
Heavy water (D2O) is used as a moderator to control nuclear fission. A moderator is a substance that is used to slow down the neutrons produced in a nuclear reaction, making them more likely to be captured by the fuel nuclei and causing further fission. Heavy water is a type of water that contains a larger amount of the isotope deuterium (D) than regular water. Deuterium has an extra neutron compared to the more common hydrogen isotope, and this makes heavy water more effective at slowing down neutrons than regular water. Lead, iron, and chromium are not typically used as moderators in nuclear reactors. Lead can be used as a shield to absorb radiation, while iron and chromium are used in the construction of the reactor vessel and other components.
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