1.
Chlorine acts as a bleaching agent only in the presence of
Correct Answer
B. Moisture
Explanation
Chlorine acts as a bleaching agent only in the presence of moisture because the chemical reaction between chlorine and water molecules produces hypochlorous acid, which is responsible for the bleaching effect. In the absence of moisture, chlorine cannot react with water and therefore cannot act as a bleaching agent.
2.
A gas that cannot be collected over water is
Correct Answer
C. Sulfur dioxide
Explanation
Sulfur dioxide is a gas that cannot be collected over water because it is highly soluble in water. When sulfur dioxide comes into contact with water, it reacts to form sulfurous acid, which makes it difficult to collect the gas. Nitrogen, oxygen, and phosphene can be collected over water as they are not highly soluble in it.
3.
The compound which gives off oxygen on moderate heating is
Correct Answer
B. Mercuric oxide
Explanation
Mercuric oxide is the compound that gives off oxygen on moderate heating. When heated, mercuric oxide decomposes into mercury and oxygen gas. This is a redox reaction where the mercuric oxide acts as the oxidizing agent and releases oxygen gas.
4.
Bromine can be liberated from potassium bromide solution by action of
Correct Answer
B. Chlorine solution
Explanation
Chlorine solution can liberate bromine from potassium bromide solution through a redox reaction. Chlorine is a stronger oxidizing agent than bromine, so it can oxidize bromide ions to bromine. This reaction occurs because chlorine has a higher affinity for electrons than bromine. When chlorine is added to a solution containing bromide ions, it will accept electrons from the bromide ions, causing them to be oxidized and forming bromine.
5.
The material used in solar cells contains
Correct Answer
B. Silicon
Explanation
Silicon is the material commonly used in solar cells due to its unique properties. It is a semiconductor that can convert sunlight into electricity through the photovoltaic effect. When light photons hit the silicon atoms, they transfer their energy to the electrons in the material, allowing them to flow as an electric current. Silicon is abundant, affordable, and has a high efficiency in converting sunlight into electricity, making it the ideal choice for solar cells.
6.
Electrical conductivity is shown by
Correct Answer
D. Graphite
Explanation
Graphite is the correct answer because it is a form of carbon that has a unique structure with layers of carbon atoms arranged in a hexagonal lattice. These layers are held together by weak intermolecular forces, allowing the electrons to move freely between the layers. This delocalized electron system gives graphite its high electrical conductivity, making it an excellent conductor of electricity. In contrast, diamond, silica, and carborundum do not have the same delocalized electron system, resulting in lower electrical conductivity.
7.
Which of the following statements regarding diamond is not correct?
Correct Answer
B. Diamond crystalizes in the body centered cubic lattice
8.
Which of the following statements regarding phosphorus is not true?
Correct Answer
D. Black phosphorus is the least stable form of the allotropes of phosphorus
Explanation
Black phosphorus is actually the most stable form of the allotropes of phosphorus, so the statement is not true. There are several allotropes of phosphorus, including white, red, violet, and black phosphorus. Black phosphorus is the most stable form at room temperature and pressure, while white phosphorus is the least stable and highly reactive.
9.
Oxygen molecule contains
Correct Answer
C. Two unpaired electrons
Explanation
The oxygen molecule contains two unpaired electrons. This means that in its electron configuration, there are two electrons that are not paired with another electron in the same orbital. Unpaired electrons are more reactive and can easily participate in chemical reactions. In the case of oxygen, these unpaired electrons allow it to form bonds with other atoms and molecules, making it a highly reactive element.
10.
Ozone is not
Correct Answer
D. A stable allotrope
Explanation
Ozone is a stable allotrope because it exists as a molecule made up of three oxygen atoms bonded together. It is relatively stable and does not easily break down into its constituent atoms. This stability allows ozone to persist in the atmosphere, where it plays a crucial role in absorbing harmful ultraviolet radiation from the sun.
11.
The gaseous iodine molecules absorb yellow light from the visible region. Its color would be
Correct Answer
D. Violet
Explanation
Gaseous iodine molecules absorb yellow light from the visible region, which means that they absorb all other colors except for yellow. When a substance absorbs certain colors of light, it appears as the complementary color of the absorbed light. In this case, since iodine absorbs yellow light, its color would appear as the complementary color of yellow, which is violet.
12.
Bubbling hydrogen sulfide through nitric acid produces
Correct Answer
C. Amorphus sulfur
Explanation
Bubbling hydrogen sulfide through nitric acid produces amorphous sulfur. Amorphous sulfur refers to a form of sulfur that lacks a definite crystalline structure. It is typically a yellow powder or solid and is formed when sulfur is rapidly cooled or precipitated from a solution. This form of sulfur is distinct from rhombic sulfur and monoclinic sulfur, which have well-defined crystalline structures. Plastic sulfur, on the other hand, is a term used to describe a specific physical property of sulfur rather than a specific form.
13.
On heating, the volume of ozone will
Correct Answer
B. Increase
Explanation
When ozone is heated, the molecules gain energy and move faster, causing them to spread out and occupy a larger volume. This increase in volume is due to the expansion of the gas as the temperature rises. Therefore, the correct answer is "increase".
14.
The semoconducting form of phosphorus is
Correct Answer
C. Black
Explanation
Black is the correct answer because the semiconducting form of phosphorus is commonly known as black phosphorus. Unlike other forms of phosphorus, black phosphorus has a layered structure with strong covalent bonds within the layers and weak van der Waals forces between the layers. It exhibits unique electrical and optical properties, making it a promising material for various applications in electronics and optoelectronics.
15.
In white phosphorus, the arrangement of phosphorus atoms is
Correct Answer
C. Tetrahedral
Explanation
White phosphorus is composed of P4 molecules, where four phosphorus atoms are arranged in a tetrahedral shape. Each phosphorus atom is bonded to three other phosphorus atoms, forming a tetrahedron. This arrangement allows for the formation of strong covalent bonds between the phosphorus atoms, resulting in the characteristic properties of white phosphorus such as its low melting point and high reactivity. Therefore, the correct answer is tetrahedral.
16.
The highest bond enthalpy is shown by
Correct Answer
B. Chlorine
Explanation
Chlorine has the highest bond enthalpy among the given options. Bond enthalpy refers to the energy required to break a covalent bond. Chlorine has a higher bond enthalpy compared to fluorine, bromine, and iodine because it has more protons in its nucleus, resulting in stronger electrostatic attraction between the nucleus and the shared electrons. This stronger attraction requires more energy to break the chlorine bond, leading to a higher bond enthalpy.
17.
Amongst the halogens, the strongest oxidizing agent is
Correct Answer
A. Fluorine
Explanation
Fluorine is the strongest oxidizing agent among the halogens. This is because fluorine has the highest electronegativity and the smallest atomic radius among the halogens. Its small size allows it to attract and gain electrons more easily, making it highly reactive and capable of oxidizing other substances. In comparison, chlorine, bromine, and iodine have larger atomic radii and lower electronegativities, which make them less effective at gaining electrons and less powerful as oxidizing agents.
18.
White phosphorus is stored
Correct Answer
B. Under water
Explanation
White phosphorus is stored under water to prevent its exposure to oxygen in the air. When white phosphorus comes into contact with oxygen, it undergoes a spontaneous combustion reaction, releasing toxic fumes and producing a bright flame. By storing it under water, the phosphorus is effectively isolated from oxygen, reducing the risk of accidental ignition. Additionally, water helps to cool down the phosphorus, further minimizing the chances of ignition.
19.
Which of the following is not the mineral of sulfur?
Correct Answer
A. Chloropatite
Explanation
Chloropatite is not a mineral of sulfur. The other three options, Fool's gold, sphalerite, and chalcopyrite, are all minerals that contain sulfur. Chloropatite, on the other hand, is a phosphate mineral that does not contain sulfur.
20.
Which statement regarding to white phosphorus is not correct? 1
Correct Answer
A. It is non poisonous
Explanation
White phosphorus is highly poisonous. When it comes into contact with the skin, it can cause severe burns and tissue damage. Inhaling its fumes or smoke can also be deadly. Therefore, the statement "It is non poisonous" is not correct.
21.
Diamond is harder than graphite
Correct Answer
A. True
Explanation
Diamond is harder than graphite because of its atomic structure. In diamond, each carbon atom is bonded to four other carbon atoms in a rigid, three-dimensional arrangement. This results in a strong, tightly packed lattice structure that makes diamond extremely hard. On the other hand, graphite has a layered structure where each carbon atom is bonded to only three other carbon atoms. These layers can easily slide over each other, making graphite soft and slippery. Therefore, diamond is indeed harder than graphite.
22.
Diamond has a high value of refractive index
Correct Answer
A. True
Explanation
Diamond has a high value of refractive index because it has a dense atomic structure and a high optical density. When light passes through diamond, it slows down and bends, causing the light to change direction. This bending of light is known as refraction. The high refractive index of diamond means that it can bend light at a greater angle compared to other materials. This property is what gives diamond its brilliance and sparkle, making it highly valued in the jewelry industry.
23.
Silicon is a non metal
Correct Answer
B. False
Explanation
Silicon is actually a metalloid, not a non-metal. Metalloids are elements that have properties of both metals and non-metals. While silicon is a poor conductor of electricity like non-metals, it also has some metallic characteristics such as being shiny and having a high melting point. Therefore, the correct answer is False.
24.
Heating of ammonium nitrate produces nitric oxide gas
Correct Answer
B. False
Explanation
Heating of ammonium nitrate does not produce nitric oxide gas. Instead, it produces nitrous oxide gas, commonly known as laughing gas. Nitric oxide gas is produced when nitric acid is heated. Therefore, the statement is false.
25.
Caustic soda has no action on red phosphorus
Correct Answer
A. True
Explanation
Caustic soda, also known as sodium hydroxide, does not react with red phosphorus. Red phosphorus is a relatively stable form of phosphorus that does not readily react with other chemicals, including caustic soda. This is why the statement "Caustic soda has no action on red phosphorus" is true.
26.
Red phosphorus glows in the dark
Correct Answer
B. False
Explanation
Red phosphorus does not glow in the dark. While white phosphorus is known to spontaneously ignite in air and emit a faint glow, red phosphorus is a more stable allotrope that does not exhibit this property. Red phosphorus is commonly used in safety matches and as a flame retardant, but it does not glow in the dark. Therefore, the correct answer is false.
27.
Red phosphorus is a polymeric substance
Correct Answer
A. True
Explanation
Red phosphorus is a polymeric substance because it consists of long chains of phosphorus atoms that are bonded together. This arrangement gives red phosphorus its solid and crystalline structure. Unlike white phosphorus, which exists as discrete P4 molecules, red phosphorus forms a network of interconnected P4 tetrahedra. This polymeric structure gives red phosphorus its unique properties, such as its lower reactivity and higher stability compared to white phosphorus.
28.
Ozone is an allotropic modification of oxygen
Correct Answer
A. True
Explanation
Ozone is an allotropic modification of oxygen because it is formed when three oxygen atoms combine to form a molecule. This is different from the usual oxygen molecule, which consists of two oxygen atoms. Ozone is a highly reactive gas and is known for its ability to absorb ultraviolet radiation in the Earth's atmosphere, forming a protective layer that shields the planet from harmful UV rays.
29.
Ozone is not poisonous in nature
Correct Answer
B. False
Explanation
Ozone is actually poisonous in nature. While it is beneficial in the Earth's upper atmosphere as it protects us from harmful ultraviolet radiation, at ground level it can be harmful to humans and other living organisms. Breathing in ozone can cause respiratory issues, such as chest pain, coughing, throat irritation, and shortness of breath. It can also worsen existing respiratory conditions like asthma. Therefore, the correct answer is False.
30.
Iron combines with chlorine forming ferrous chloride
Correct Answer
B. False
Explanation
Iron can combine with chlorine, but it forms ferric chloride, not ferrous chloride. Ferrous chloride is formed when iron combines with chlorine in the presence of excess hydrochloric acid. In this reaction, iron is oxidized from its ferrous state (Fe2+) to its ferric state (Fe3+), resulting in the formation of ferric chloride. Therefore, the correct answer is false.