Cargando....
|
Mantén pulsado para arrastrar. |
|||
|
Haz clic aquí para cerrar |
|||
Pregunta 1 Informe
Which of the following is a disaccharide?
Detalles de la respuesta
Sucrose is a disaccharide. A disaccharide is a type of carbohydrate made up of two monosaccharides linked together by a glycosidic bond. Sucrose, also known as table sugar, is composed of glucose and fructose joined together by a glycosidic bond. The other options listed are not disaccharides; fructose is a monosaccharide, starch, cellulose, and glycogen are polysaccharides.
Pregunta 2 Informe
What amount of copper is deposited when 13.0g of zinc reacts with excess copper (ll) tetraoxosulphate (IV) solution according to the following equation? Zn (s) + CuSO4(aq) → ZnSO4(aq) + Cu (s) [Cu =63,5, Zn = 65]
Detalles de la respuesta
Pregunta 3 Informe
What volume of carbon (lV) oxide is produced at s.t.p. when 2.5g of CaCO3 reacts with excess acid according to the following equation? CaCO3 + 2HCI → CaCI2 +H2O + CO2 [CaCO3 = 100; molar volume of a gas at s.t.p = 22.4dm3]
Detalles de la respuesta
The balanced equation for the reaction between CaCO3 and 2HCI is: CaCO3 + 2HCI → CaCI2 + H2O + CO2 The molar mass of CaCO3 is 100 g/mol, which means that 100 g of CaCO3 will produce 1 mole of CO2. Therefore, 2.5 g of CaCO3 will produce: 1 mole CO2 = 22.4 dm3 at s.t.p. x moles CO2 = (2.5 g / 100 g/mol) = 0.025 moles x = 0.56 dm3 (rounded to two decimal places) Therefore, the volume of CO2 produced at s.t.p is 0.56 dm3. Hence, the answer is (d) 0.56 dm3.
Pregunta 4 Informe
What amount of hydrogen will be required for complete hydrogenation of one mole of pent-3-yne?
Detalles de la respuesta
Pregunta 5 Informe
During water treatment for town supply, water is passed through layers of send beds in order to
Detalles de la respuesta
During water treatment for town supply, water is passed through layers of sand beds in order to filter the water. The sand beds act as a physical barrier that separates large particles, sediments, and debris from the water. As the water flows through the sand bed, the sand traps the suspended particles, and clean water passes through. This process is called filtration and is an essential step in water treatment, as it removes impurities and improves the quality of the water. The filtered water can then be treated further to remove any remaining impurities or disinfect it to kill any harmful bacteria and viruses.
Pregunta 7 Informe
Use this following information to answer this question. Compound X was boiled with concentrated hydrochloric acid for a long time. One of the products was found to be a sugar. What type of reaction was involved between compound X and concentrated hydrochloric acid?
Detalles de la respuesta
The reaction between compound X and concentrated hydrochloric acid involves hydrolysis. Hydrolysis is a type of chemical reaction in which a compound is broken down into two or more simpler compounds through the addition of water. In this case, the concentrated hydrochloric acid acts as a catalyst, promoting the breakdown of compound X into simpler compounds, one of which is a sugar. Therefore, the reaction between compound X and concentrated hydrochloric acid is a hydrolysis reaction.
Pregunta 8 Informe
If the third member of a homologous series is C3H8, the fifth member will be
Detalles de la respuesta
A homologous series is a series of organic compounds having the same functional group and similar chemical properties in which the successive members differ by a CH2 unit. So, the general formula of the homologous series would be CnH2n+2. If the third member of a homologous series is C3H8, it means that the general formula of the series is CnH2n+2, where n = 3. C3H8 belongs to the alkane series, so the fifth member of the series would also belong to the alkane series and have the general formula CnH2n+2, where n = 5. Substituting n = 5 in the general formula, we get C5H2(5)+2 = C5H12. Therefore, the fifth member of the homologous series would be C5H12.
Pregunta 9 Informe
Which of the following is not correct about a catalyst? It
Detalles de la respuesta
The statement that is not correct about a catalyst is: "can start a chemical reaction which will normally not take place." A catalyst cannot start a chemical reaction that will normally not take place because a catalyst only speeds up the rate of an existing reaction. It works by lowering the activation energy required for a reaction to occur, thus making it easier for the reaction to take place. Once the reaction is completed, the catalyst remains unchanged and can be used again. Therefore, options a, b, d, and e are all correct statements about a catalyst, while the statement in option c is not correct.
Pregunta 10 Informe
Nitrogen is prepared on a large scale by the
Detalles de la respuesta
Nitrogen is prepared on a large scale by the fractional distillation of liquefied air. Air is composed of about 78% nitrogen and 21% oxygen, along with other gases. To obtain nitrogen, the air is liquefied by compressing and cooling it to a very low temperature. This liquefied air is then separated into its components by fractional distillation, a process in which the different gases are separated based on their boiling points. Since nitrogen has a lower boiling point than oxygen, it boils off first and can be collected. This process is used to obtain large amounts of nitrogen for industrial and commercial purposes.
Pregunta 11 Informe
When an atom gains an electron, it becomes properties
Detalles de la respuesta
When an atom gains an electron, it becomes negatively charged because it now has more electrons than protons. This negatively charged atom is called an anion. The extra electron is held by the nucleus through the electromagnetic force and affects the chemical properties of the atom. The anion has a greater affinity for positively charged ions or cations and can undergo chemical reactions, forming compounds with other atoms or ions. Therefore, the correct option is "negatively charged."
Pregunta 12 Informe
When acidified KMnO4 solution is decolorised by ethene, the gas acts as
Detalles de la respuesta
When acidified KMnO4 solution is decolorised by ethene, it means that ethene is oxidised to a colorless compound and KMnO4 is reduced. Therefore, ethene is acting as a reducing agent. So, the correct option is (c) a reducing agent.
Pregunta 13 Informe
Which of the following equations represents a neutralization reaction?
Detalles de la respuesta
The equation that represents a neutralization reaction is: H2SO4 + KOH → KHSO4 + H2 O. In this reaction, an acid (H2SO4) reacts with a base (KOH) to form a salt (KHSO4) and water (H2O). Neutralization reactions involve the combination of an acid and a base to form a salt and water, with the acid and base neutralizing each other's acidic and basic properties. The other options either do not involve an acid and a base or do not form a salt and water, and thus do not represent neutralization reactions.
Pregunta 14 Informe
Which of the following exhibits resonance?
Detalles de la respuesta
Benzene exhibits resonance. Resonance is a phenomenon in which electrons move between different possible locations within a molecule, resulting in the stabilization of the molecule. In benzene, the carbon atoms are arranged in a ring with alternating double bonds and single bonds. The electrons in the double bonds are delocalized and move freely around the ring, resulting in a more stable molecule. This is an example of resonance. The other molecules listed do not have a similar arrangement and therefore do not exhibit resonance.
Pregunta 15 Informe
On exposing palm wine to air for some days, it becomes sour owing to the conversion of
Detalles de la respuesta
Palm wine is a fermented beverage that is produced from the sap of certain palm trees. The fermentation process is mainly carried out by yeast, which converts glucose to ethanol. When palm wine is exposed to air, the ethanol undergoes oxidation, which results in the formation of ethanoic acid. This is what causes the sour taste of the palm wine. Therefore, the correct answer is "ethanol to ethanoic acid."
Pregunta 16 Informe
Which of the following statements is not correct about electrolysis?
Detalles de la respuesta
The statement that is not correct about electrolysis is "Reduction occurs at the anode". During electrolysis, reduction occurs at the cathode and oxidation occurs at the anode. At the anode, positively charged ions (cations) lose electrons to become neutral atoms or molecules. At the cathode, negatively charged ions (anions) gain electrons to become neutral atoms or molecules. Anions migrate to the anode, while positive ions migrate to the cathode. The concentration of the electrolyte affects the rate of the reaction and the discharge of ions. Electrolytes conduct electric current because they contain ions that are free to move and carry charge.
Pregunta 17 Informe
Ammonia gas is suitable for performing the 'Fountain' experiment because the gas is
Detalles de la respuesta
Ammonia gas is suitable for performing the 'Fountain' experiment because it is very soluble in water. In the experiment, ammonia gas is passed through water, where it dissolves to form an alkaline solution. The gas bubbles produced rise to the top of the solution, and as more gas bubbles are produced, the solution becomes saturated with the gas. Eventually, the pressure of the gas forces the solution to rise up and out of the container, creating a fountain-like effect. Ammonia gas is preferred for this experiment because of its high solubility in water, which allows for a sufficient amount of gas to dissolve in the solution and produce the necessary pressure for the fountain effect.
Pregunta 18 Informe
Which of the following metals will be the most suitable for use where lightness and resistance to corrosion are of importance?
Detalles de la respuesta
The most suitable metal for use where lightness and resistance to corrosion are of importance is Aluminium. This is because Aluminium is a lightweight metal that has a low density and is resistant to corrosion. Aluminium forms a protective layer of oxide on its surface that prevents further oxidation, making it highly resistant to corrosion. In addition, Aluminium is a good conductor of heat and electricity and can be easily shaped into different forms, making it useful for a wide range of applications, such as in the aerospace and automotive industries, where weight reduction and corrosion resistance are critical factors. Therefore, the correct answer is Aluminium.
Pregunta 20 Informe
The products formed when sodium hydrogen trioxocarbonate (IV) is heated strongly are
Detalles de la respuesta
Pregunta 21 Informe
In which of the following compounds is the oxidation number of nitrogen equal to + 3?
Detalles de la respuesta
The oxidation number of an element is the hypothetical charge it would have if all its bonds were purely ionic. In other words, it is a measure of the degree of oxidation of an atom in a molecule. To determine the oxidation number of nitrogen in each compound, we need to know the electronegativity of the other elements involved in the bond. In NO2, the electronegativity of oxygen is higher than nitrogen, so nitrogen is assigned an oxidation number of +4. In N2O, the oxidation number of nitrogen is +1. In NO, nitrogen is assigned an oxidation number of +2. In HNO2, nitrogen is assigned an oxidation number of +3. In HNO3, nitrogen is assigned an oxidation number of +5. Therefore, the only compound in which the oxidation number of nitrogen is equal to +3 is HNO2.
Pregunta 22 Informe
The component of air that can be removed by alkaline pyrogallol solution is
Detalles de la respuesta
Alkaline pyrogallol solution is commonly used to remove oxygen from a gas mixture. This is because pyrogallol can easily react with oxygen in the air to form a brown precipitate. Therefore, the component of air that can be removed by alkaline pyrogallol solution is oxygen.
Pregunta 23 Informe
What does X represent in the following equation? H 2(g) + 1/2O2(g) → H2O (l); ∆H = xKJ.
Detalles de la respuesta
In the given chemical equation, X represents the Enthalpy of Formation. Enthalpy of formation (∆Hf) is defined as the amount of heat energy released or absorbed when one mole of a compound is formed from its constituent elements in their standard states under standard conditions. In the given equation, the reactants are hydrogen gas and oxygen gas in their standard states, and the product is liquid water. The value of ∆H represents the amount of heat energy that is either released or absorbed when one mole of water is formed from its constituent elements. If the value of ∆H is negative, it means that the reaction is exothermic, i.e., heat energy is released during the reaction, while a positive value of ∆H represents an endothermic reaction, i.e., heat energy is absorbed during the reaction.
Pregunta 24 Informe
An arrangement of two different metals in aqueous solutions of their salts to produce an electronic current is known as
Detalles de la respuesta
An arrangement of two different metals in aqueous solutions of their salts to produce an electronic current is known as an electrochemical cell. This is because the cell involves a chemical reaction that converts chemical energy into electrical energy. One of the metals acts as a negative electrode and the other as a positive electrode, and the movement of electrons between them through the salt bridge or porous membrane generates an electric current. This process is used in batteries and other electronic devices to produce electrical energy.
Pregunta 25 Informe
The alkali metals exhibit similar chemical properties because
Detalles de la respuesta
The alkali metals are a group of elements in the periodic table that include lithium, sodium, potassium, rubidium, cesium, and francium. They exhibit similar chemical properties because they all have one valence electron in their outermost shell, which they readily give up to form positive ions. This makes them highly reactive and they are easily oxidized in air or water. The similarity in their electronic configuration results in similar chemical behavior, such as the ability to form ionic compounds with non-metals and the tendency to react vigorously with water to produce hydrogen gas and an alkali metal hydroxide.
Pregunta 26 Informe
''Equal volumes of all gases at the same temperature and pressure contain the same number of molecules'' is an expression of
Detalles de la respuesta
The statement ''Equal volumes of all gases at the same temperature and pressure contain the same number of molecules'' is an expression of Avogadro's Law. This law is named after the Italian scientist Amedeo Avogadro, who discovered that the volume of a gas is directly proportional to the number of molecules or atoms present, provided that the temperature and pressure remain constant. This law can be used to determine the molar volume of gases and is important in many fields of science, such as chemistry and physics. In simple terms, this law states that two gases at the same temperature and pressure will have the same number of molecules in a given volume, regardless of their chemical identity or atomic/molecular weight.
Pregunta 27 Informe
The cleansing action of soap in hard water is not satisfactory because soap
Detalles de la respuesta
Soap is made up of sodium or potassium salts of long-chain fatty acids. The cleaning action of soap is due to its ability to dissolve in water and attach to oil and dirt particles, enabling them to be washed away. However, in hard water, which contains dissolved calcium and magnesium ions, soap forms insoluble salts with these ions. These salts, called scum, are insoluble in water and stick to surfaces, reducing the effectiveness of the soap. As a result, the cleansing action of soap in hard water is not satisfactory.
Pregunta 28 Informe
What is the role of MnO2 in the reaction represented by the following equation?MnO2 + 4HCI2 + CI2 + 2H2O
Detalles de la respuesta
Pregunta 29 Informe
The following salts will produce a gas on reacting with hydrochloric acid except
Detalles de la respuesta
Pregunta 30 Informe
The existance of two or more forms of the same element in the same physical state is known as
Detalles de la respuesta
The existence of two or more forms of the same element in the same physical state is known as allotropy. Allotropy is the property of some elements to exist in two or more different forms, called allotropes. These allotropes have different physical and chemical properties due to the different arrangements of atoms in their crystal lattice structures. For example, carbon has three common allotropes: diamond, graphite, and fullerene. Each of these allotropes has different physical and chemical properties despite being made up of the same element.
Pregunta 31 Informe
Use this following information to answer this question. Compound X was boiled with concentrated hydrochloric acid for a long time. One of the products was found to be a sugar. Compound X was probably
Detalles de la respuesta
The fact that a sugar was produced by boiling Compound X with concentrated hydrochloric acid suggests that Compound X was likely a carbohydrate, specifically a type of polysaccharide such as cellulose. When polysaccharides undergo hydrolysis (a reaction with water), they are broken down into their constituent monosaccharides (simple sugars) by the addition of water molecules. Therefore, the production of a sugar as a product of the reaction between Compound X and hydrochloric acid suggests that the reaction involved hydrolysis of the polysaccharide. The other compounds listed (rubber, polyethylene, nylon, and ethanol) are not polysaccharides and would not be expected to produce a sugar upon hydrolysis.
Pregunta 32 Informe
The rate of production of hydrogen gas from the reaction between zinc granules and hydrochloric acid can be increased by
Detalles de la respuesta
The rate of production of hydrogen gas from the reaction between zinc granules and hydrochloric acid can be increased by using zinc powder instead of zinc granules. The rate of reaction between zinc and hydrochloric acid is determined by the surface area of the zinc that is exposed to the acid. Zinc powder has a higher surface area than zinc granules, which increases the rate of reaction between the zinc and the acid. Cooling the reaction mixture would slow down the reaction rate because the reaction is exothermic and releasing energy as heat, and lowering the temperature would reduce the kinetic energy of the reacting particles. Using a zinc rod instead of zinc granules would not increase the surface area, but would decrease it, slowing down the reaction rate. Carrying out the reaction at a higher pressure or in a closed vessel would not increase the surface area of the zinc and would not affect the rate of reaction.
Pregunta 33 Informe
When excess carbon (lV) oxide is passed into lime water, the turbidity produced initially disappears due to the formation of
Detalles de la respuesta
Pregunta 34 Informe
A solution of pH 7 is
Detalles de la respuesta
A solution of pH 7 is neutral. The pH scale ranges from 0 to 14, with pH 7 being the midpoint of the scale. A pH of 7 indicates a balance of hydrogen ions (H+) and hydroxide ions (OH-) in the solution, with equal concentrations of both ions. In other words, a neutral solution is neither acidic nor basic.
Pregunta 35 Informe
What is the likely formula of compound formed between element M in group two and element X in group seven?
Detalles de la respuesta
When elements in group two (alkaline earth metals) react with elements in group seven (halogens), they form ionic compounds with a general formula of MX2. Therefore, the likely formula of the compound formed between element M in group two and element X in group seven is MX2.
Pregunta 36 Informe
The following are properties of transition metals except
Detalles de la respuesta
The incorrect statement about transition metals is "low melting points". Transition metals are characterized by a high melting and boiling point due to their strong metallic bonding, which involves the delocalization of electrons over a large number of atoms. Other properties of transition metals include variable oxidation states, tendency to form complex ions, formation of coloured ions, and ability to act as catalysts.
¿Te gustaría proceder con esta acción?