Solution: Lead and tin alloys are used to make solder. It is 50 per cent lead (Pb) and 50 per cent tin (Sn) in composition. Solder has a very low melting point, even lower than the metals that make...
Solution: Because gold and platinum are non-reactive metals, they do not corrode.
Solution: Gold is a chemically inert metal. So that they don't corrode readily when exposed to air, water vapour, and other gases in the atmosphere. That is why gold retains its novelty even after...
Solution: Because aluminium metal corrodes when exposed to humid air, a new aluminium vessel loses its lustre quickly after usage. This occurs when the oxygen in the air combines with the aluminium...
Solution: Copper and tin are combined to form the bronze alloy. It is made up of 90% copper and 10% tin. It is greatly useful in the production of statues and coins.
Solution: The silver objects slowly form a thin layer of silver sulphide from the hydrogen sulphide gas existing in the air. Silver items tarnish due to the coating.
Solution: Silver tarnishes slowly when exposed to hydrogen sulphide gas in the air. Silver combines with hydrogen sulphide gas in the air to generate a thin silver sulphide coating.
Solution: In the presence of hydrogen sulphide gas in the air, silver metal turns black. Silver(Ag) combines with hydrogen sulphide gas in the air to generate a thin silver sulphide (Ag2S)...
(a) What happens during a bee sting? What is its remedy? (b) What happens during a wasp sting? What is its remedy? (a) When a bee stings you, it injects an acidic liquid into your body, causing...
(a) Explain the pH change as the cause of tooth decay. How can tooth decay caused by pH change be prevented? (b) Explain how pH change in the lake water can endanger the lives of aquatic animals...
(a) During an ant’s sting? (b) During the nettle leaf hair sting? How can the effect of these stings be neutralised? (a) During an ant's sting, methanoic acid is injected into the victim's skin....
The element fluorine is in group 17 of the periodic table, which is also known as the halogen group, and has a valency of 1. So, all the elements in the halogen group will have a valency equal to 1.
All elements in the same column of the periodic table as boron have 3 valence electrons in their ultimate shell.
(a) In group 1 of alkali metals, the chemical reactivity increases down the group from lithium to francium. (b) In group 17 of halogen elements, the chemical reactivity decreases down the group from...
Silver, gold and platinum are used to make jewellery. Solution: Because the metals used in jewellery are always chosen on the basis of their reactivity, platinum, gold, and silver are utilised to...
Solution: Steel and stainless steel are two types of iron alloys. Iron is present in steel in amounts ranging from 0.1 to 1.5 per cent. Iron, nickel, and chromium are all present in stainless...
As we move from left to right in a period, the tendency of atoms to lose electrons decreases as the force of attraction between the nucleus and electrons increases. This is because the number of...
Solution: One way in which iron is not covered with anything is to alloy it with chromium and nickel to generate stainless steel (which does not rust).
Solution: The presence of oxygen and water with a slightly acidic pH level are both required for rusting iron to take place. Grease coating can be applied to iron to keep it from rusting because it...
As we move from left to right in a period, the tendency of atoms to gain electrons increases as more and more electrons get accommodated in the same shell.
As we move horizontally from left to right, the following things happen: (i) Metallic character decreases. (ii) Atomic size decreases.
Solution: Electrolytic refining is the technique of electrolysis used to refine a metal (usually copper). When it comes to the mechanics of the process, a large chunk or slab of impure metal serves...
Solution: Pure gold is 24-carat. Karat, also spelt Carat, is a measure of the fineness (i.e., purity) of gold. A gold karat is 1/24 part, or 4.1667 per cent, of the whole, and the purity of a gold...
Solution: A mercury amalgam is a mixture of mercury and another metal. Depending on the percentage of mercury, it can be a liquid, a soft paste, or a solid. The electrolysis of brine in cells with a...
Solution: The solder alloy comprises 50 per cent lead (Pb) and 50 per cent tin (Sn). It has a very low melting point, which is far lower than the melting points of its constituent metals (Pb and...
Solution: Solder.
Solution: The reducing agent that can be used to extract manganese from manganese dioxide is aluminium powder. Manganese is displaced from manganese dioxide by the more reactive aluminium. In other...
Carbonate and sulphide ores are usually converted into oxides during the process of extraction of metals. Solution: Carbonates are converted to oxides by rapidly heating them in a little amount of...
Solution: To keep iron things from corroding, they are painted. When air and moisture come into contact, there's a good probability that the iron may rust.
Solution: Zinc is a reactive metal, and when air comes into contact with it, it generates a thin layer of zinc oxide that is hard and impenetrable to air, preventing corrosion of both zinc and...
Solution: Zinc. Because zinc oxidises and experiences acid corrosion “sacrificially” to steel, it is used in the galvanising process instead of other metals. When zinc comes into contact with steel,...
Solution: The process of putting a protective zinc coating to iron or steel to prevent rusting is known as galvanisation or galvanization (or galvanising). The most popular procedure is hot-dip...
Solution: The rusting of iron can be avoided if (i) Applying paint to the surface. (ii) By smearing grease or oil on the surface.
Solution: Reduction is the exchange of electrons between species in a chemical reaction involving the gain of electrons or a reduction in an element's oxidation state. In a reduction chemical...
Solution: Calamine (ZnCO3) is a zinc ore that produces carbon dioxide when exposed to dilute acid.
(a) Ethene (b) Methane (c) Ethyne (d) Nitrogen Solution: Option (c) is the answer. Ethyne has a triple bond between the two carbon atoms.
b) 1.5cm is the right answer. The object must be placed between the pole and focus, so the correct anser is c.
The correct answer is b) at the reflector's focus
c) 0 degree is the right answer. A ray of light travelling through the concave mirror's centre of curvature lands properly on the mirror, retracing its course.So, for a ray of light travelling...
d) at infinity is the right answer.
The correct answer is c) at the centre of the curve.
d) between pole and focus is the correct answer.
The correct option is b) at a distance larger than the radius of curvature is the right answer The image created by a concave mirror for an object positioned beyond the centre of curvature or at a...
The correct answer is c) between focus and curvature centre.
a) I A enlarged image is created when an object is put between the pole and the focus of a concave mirror. ii) A enlarged image is created when an item is placed between the focus and the centre of...
a) I When an object is put between the pole and the focus of a concave mirror, the image created is virtual, erect, and bigger than the object, and it is formed behind the mirror. ii) When an item...
The following are some of the applications for concave mirrors: a) Concave mirrors are utilised as shaving mirrors because they provide an enlarged and erect image, which aids in a smooth shave. b)...
Concave mirrors are utilised as shaving mirrors because they provide a magnified picture that is upright in nature when the face is put close to the mirror. As a result, a smoother shave is possible.
A concave mirror is used by dentists. The dentist positions the concave mirror so that the tooth is in focus. The dentist sees an enlarged picture of the tooth, which aids them in inspecting the...
In a solar furnace, a concave mirror is employed. A huge concave reflector is used to focus the sun on the solar furnace. When light rays strike the concave mirror's surface, they are reflected and...
The item should be placed far enough away from the concave mirror for the image to develop at the focus when calculating the focal length of a concave mirror. This is accomplished by utilising a...
a) A converging mirror reflects a genuine image b) A converging mirror creates a virtual image
The object must be placed between the focus and the pole of the concave mirror to create an upright enlarged picture. AD is drawn parallel to the primary axis in the image below, thus D is reflected...
a) Between the pole and the mirror's focus for erect and virtual b) Infinity, at the mirror's focal point c) At the mirror's centre of curvature, for the same size as the object
A torch reflector is made of a concave mirror.
The mirror's focal length, f = 10cm The item is positioned at a distance of = 8cm. As a result, the item can be considered to be between the pole and the concave mirror's focus. As a result, the...
The picture generated when an item is positioned at the centre of curvature, C, of a concave mirror is as follows: a) at the centre of the curve b) inverted and actual c) the image's size is the...
The picture generated when an item is positioned at the centre of curvature, C, of a concave mirror is as follows: a) at the centre of the curve b) inverted and actual c) the image's size is the...
A minimum of two rays are required to locate the image generated by a concave mirror. The ray diagram for the creation of a virtual image by a concave mirror is as follows:
Because the angle between the angle of incidence and the angle of reflection is 0 degrees and the light rays strike the surface at right angles, a beam of light travelling through the centre of...
The headlights of an automobile have a concave mirror. The light rays diverge and are gathered by the concave reflector, which is then reflected back as a powerful and parallel-sided beam of light...
A dental mirror can be made out of a concave mirror.
The light ray's direction after reflection is as follows. The light ray's direction after reflection is as follows.
When an object is outside of the curvature's centre of curvature.
At the focus, the picture is produced.
At infinity, the picture is obtained.
When an object is positioned between the focal point and the curvature's centre of curvature.
Between the pole and the focus, the item should be positioned.
When an object is placed in the concave mirror's centre of curvature, the image generated is real, inverted, and equal in size to the thing.The ray diagram is shown below:
a) 25cm is the right answer.
b) 15cm is the right answer.
b) R = 2f is the right answer.
A convex mirror is the best solution.
The right answer is c) a protruding surface.
a) I Principal focus of a convex mirror: The principal focus of a convex mirror occurs when all of the reflected light rays meet at a location after diverging in the mirror. ii) Focal length of a...
a) I A concave mirror's primary focus is the place on the principal axis where all of the light rays converge after reflection. ii) Focal length of a concave mirror: The focal length of a concave...
a) Curvature centre: This is the centre of a hollow glass sphere, of which a mirror is a component. b) Curvature radius: This is the radius of the hollow glass sphere in which a mirror is contained....
The light beams deviate from the primary focus after reflection, which is why a convex mirror is also known as a diverging mirror
As the parallel beam of light rays is converged by the concave mirror after reflection, all of the parallel light rays converge at the primary focus. This is why it is referred to as a converging...
A spherical mirror's focal length and radius of curvature are related as follows: R/2 = f Given, R is equal to 25 cm We already know that f = R/2. As a result, f = 12.5cm
Concave and convex mirrors are two forms of spherical mirrors. a) Mirror with a convex surface b) Mirror with a concave surface
A spherical mirror is a hollow sphere of glass that serves as a reflecting surface. Concave and convex mirrors are the two kinds of spherical mirrors. The following are the differences between a...
a) The main emphasis b) The main emphasis b) The convergence and divergence of data d) The main emphasis
f = 25cm focal length Calculate R We are aware of this. R/2 = f 2f = R R equals 50cm
R = 32cm radius of curvature f = focal length f = focal length f = focal length f = focal length f = focal length We are aware of this. R/2 = f 16cm f = 32/2
The focus of a convex mirror is behind it.
a) Mirror with a convex surface b) Mirror with a concave surface
d) 9.25 is the correct answer.
Option (b) is the answer.
B) virtual, behind the mirror, and the same size as the item is the right option.
Option (c) is the answer.
The best choice is a) virtual.
Option (b) is the answer.
Option (c) is the answer.
c) 0 degree is the right answer.
Option (d) is the answer.
Option (c) is the answer.
b) 60 degrees is the right answer. Explanation: Since the angle of incidence equals the angle of reflection and it is given that the angle of incidence is 30 degrees. The incident beam will be...
a) Always is the proper option.
Option (c) is the answer.
Option (c) is the answer.
a) We can see the picture of our face in a plane mirror but not on a sheet of paper because the image created on a plane mirror is known as regular reflection, but the image formed on a sheet of...
Option is (c) is the answer.
Option (d) is the answer.
The ray diagram of an image formed on a plane mirror when a light source is placed in front of it is shown below. Consider a point source of light O which is placed in front of a mirror MM’. The...
Option (b) is the answer.
Option (b) is the answer.
The modern periodic table was prepared by Henry Moseley.
The phenomenon of light reflection occurs when a light beam bounces back from a surface. a) Incident ray: The beam of light that strikes the mirror. b) Angle of incidence: The angle at which the...
(a) Anomalies of Mendeleev’s periodic table: 1. Elements are arranged in increasing order of atomic number in modern periodic table, thus there was no need for keeping more than one element in one...
The phenomenon of light reflection occurs when a light beam bounces back from a surface. a) Incident ray: The beam of light that strikes the mirror. b) Angle of incidence: The angle at which the...
(a) The modern periodic law states that the physical and chemical properties of an element is a periodic function of its atomic number. (b) The elements are arranged in the increasing order of...
(a) Limitations of Mendeleev’s classification of elements: (i) It failed to explain the position of isotopes. (ii) The wrong order of atomic masses of some elements could not be explained. (iii) The...
b) Plane mirror applications: It's used to make periscopes, for example. ii) Used to see ourselves in our houses. iii) It may also be utilised as a decorative item.
a) The width of the boy's mouth picture is 5cm, and the image is created at a distance of 2m behind the mirror. b) The speed with which the kid approaches the mirror will be the same as the speed...
(a) The physical and chemical properties of the elements are a periodic function of their atomic masses. It was the discovery of atomic number which led to a change in Mendeleev’s periodic law which...
Because of a similarity in their chemical properties, the two isotopes of chlorine have the same atomic number and chemical properties. The arrangement of elements is on the basis of increasing...
We cannot see anything in a fully black room because there is no light. a) We can see the light from the electric bulb. b) Because white paper is visible, it reflects light back from the electric...
The light beams move parallel to each other and are reflected in a similar manner in regular reflection, but in diffused reflection, the parallel beam of light is reflected in all directions. a)...
(a) In order to make sure that the elements having similar properties lie in the same vertical column (group), Mendeleev left some gaps in his periodic table. (b) The noble gases were not discovered...
a) Because a wall has a rough surface, when a parallel beam of light strikes it, the reflection is dispersed, whereas the surface of the mirror is smooth, and the reflection is regular. a)...
(a) The elements are classified according to the properties possessed by the elements. Elements with similar properties fall in the same group and thus large number of elements got restricted to a...
The lateral inversion difference exists between looking at an image and looking at oneself. However, this does not occur in photographs.
Ambulance is written this way so that when it shows in the rear-view mirror of the car in front of it, the driver can see it correctly due to lateral inversion and make room for it.
When an object is put in front of a plane mirror, the image received on the other side seems to be on the left side. The term "lateral inversion" refers to a shift in the sides of an item and its...
(a) Eka-aluminium and gallium are the two different names for a single element. Eka-aluminium has same property like density, melting point etc as gallium element and it was proposed before the...
(a) Merits: 1. Predicted the existence of certain elements such as gallium, scandium and germanium. 2. Predicted the properties of various elements based on their positions in the periodic table. 3....
b) The name of the phenomenon involved is lateral inversion
The difference between a real picture and a virtual image is that a real image can be obtained on a computer screen, but a virtual image cannot. The image created on the screen in a movie theatre is...
Given, The incidence angle is 30 degrees. The rules of reflection tell us that angle of incidence equals angle of reflection. As a result, the angle of reflection is 30 degrees.
On the opposite side of the mirror.
A student says that we can see an object because light from our eyes is reflected back by the object is false
(a) According to Mendeleev’s periodic law, the physical and chemical properties of elements are a periodic function of their atomic masses. It was the discovery of atomic number which led to a...
(i) It was not applicable throughout the arrangements of elements in the periodic table. (ii) Those elements discovered after Newland’s octaves did not follow the law of octaves. (iii) The position...
When light is reflected, the angles of incidence and reflection are equal
Virtual pictures are the term for such visuals.
Light follows a straight path.
At a distance equal to the distance at which the object is positioned, the image is produced behind the mirror.Given, 10cm between the item and the mirror 10cm between the mirror and the picture As...
(a) Yes, Dobereiner's triads also exist in the columns of Newlands’ Octaves. This can be explained by taking the second column of the Newland’s classification of elements which has the elements...
According to the Newlands’ law of octaves, when elements are arranged in the order of their increasing atomic masses, the properties of the eighth element (starting from a given element) occur in a...
The term "lateral inversion" refers to this occurrence.
Lateral inversion is the term for this occurrence.
According to Dobereiner’s law of triads, when elements in the periodic table are arranged in an increasing order of their atomic masses, a group of elements share similar chemical properties. This...
Helium, Neon, Argon are completely filled and appear under the category of noble gases.
It is necessary to use a plane mirror.
a) A virtual representation b) Photographic image
a)Angle of incidence is 0 degrees b)Angle of reflection is 0 degree
(a) Lithium, Sodium, Potassium are the elements having single electron in their outermost electron. They come under the category of alkali metals. (b) Magnesium and calcium have two electrons in...
Metalloid is the name of the group of elements which divide metals and non-metals in periodic table. They are the elements which share the properties of both metals and non-metals.
The mirror surface is at a 40-degree angle. The incidence angle is 90-40 = 50 degrees. As a result of the rules of reflection, the angle of reflection is 50 degrees.
The angle of incidence equals the angle of reflection, according to the principles of reflection. As a result, the angle of reflection will be 30 degrees.
The angle of incidence is 0 degrees when a beam of light falls properly on the surface of a flat mirror. We know that the angle of incidence equals the angle of reflection because of reflection...
(a) Metals are placed in left side of the periodic table. (b) Non-metals are placed in right side of the periodic table.
Hydrogen is placed at the topmost position of the periodic table because it resembles the properties of both alkali metals and halogens each. But it is placed in first group above the alkali metals...
(a) Isotopes of an element are species that have the same atomic number but different atomic mass. So they are not given separate place in periodic table and are based on the atomic number of that...
(a) In the modern periodic table, only lithium and beryllium are the metals among the first ten elements and the rest are non-metals. (b) The significance of atomic numbers in the periodic table is...
Two examples of each category are as follows: (i) Group 1: Lithium and Sodium. (ii) Group 17: Fluorine and Chlorine. (iii) Group 18: Neon and Argon.
(a) (i) The vertical column of the periodic table is known as a group. (ii) The horizontal row of elements in a periodic table is known as a period. (b) In total, there are seven periods and...
(a) Noble Gases. (b) Eighth.
(a) Atomic number. (b) Periods.
(a) Alkali metals. (b) Halogens.
The noble gases could be placed in Mendeleev’s periodic table later on, without disturbing the original order. Noble gases which are chemically least reactive and more stable could be placed in the...
Lithium, sodium and potassium are said to be one of the triads in the Mendeleev’s periodic table. Lithium (atomic mass 7) is the first element in the triad and sodium being in the middle has atomic...
Eka- Aluminium (gallium) and Eka-Silicon (germanium) are the two elements whose properties were predicted on the basis of their positions in the periodic table without getting into details of the...
Scandium, Gallium, Germanium are the three elements predicted by Mendeleev from the gaps in his periodic table and were known as eka-boron, eka – aluminium and eka-silicon.
Gallium and Scandium are the two elements whose properties are predicted on the basis of their positions in Mendeleev’s periodic table without going into further details.
The factors that guided Mendeleev to classify the elements were: 1. Increasing atomic masses. 2. Grouping together the elements having the same physical and chemical properties.
As per Mendeleev, the basis for the classification of elements was atomic mass.
There will be six elements in between X and Y since X and Y are the two elements having similar properties and obey Newlands law of octaves.
As per Dobereiner’s triad, the atomic mass of the middle element is the average of the atomic mass of first and third element. Given, Mass of A = 7 Mass of C = 39 Mass of B = (7+39)/2 =...
The scientists who gave the respective laws are: (a) Newlands gave the law of octaves. (b) Dobereiner gave the law of triads.
(a) Periods have elements with consecutive atomic numbers. (b) The given statement is correct. (c) The given statement is correct.
The scientist who said that the properties of elements are a periodic function of their atomic masses was Mendeleev.
False. The elements in a period have consecutive atomic numbers and not in the group.
(a) False. Newlands divided the elements into horizontal rows of seven element each and the first and last elements ended up on the same note. (b) False. According to Mendeleev’s periodic law, the...
(a) Mendeleev arranged the elements in his periodic table on the basis of atomic masses. (b) Now, the elements are arranged on the basis of atomic numbers.
(a) CO2 (b) O2 (c) C2H4 (d) C2H2 Solution: Option (c) is the answer. The electronic configuration of the atoms: C: 1s2 2s2 2p2 H: 1s1 One sigma bond and one pi bond make up a double bond. We have a...
(a) Oxygen and ethyne (b) Carbon dioxide and ammonia (c) Methane and ethane (d) Nitrogen and ethyne Solution: Option (d) is the answer. Nitrogen: Because each nitrogen atom requires three electrons...
(a) Hydrogen (b) Oxygen (c) Water (d) Ammonia Solution: Option (b) is the answer. Each oxygen atom only has six electrons and needs two more to complete its outer shell. As a result, the two...
(a) Ar (b) Ne (c) He (d) Kr Solution: Option (c) is the answer. The least reactive of all known elements are noble gases. Because they each have eight valence electrons, their outer energy levels...
(a) 20 (b) 19 (c) 18 (d) 16 Solution: Option (c) is the answer. Its ion Y2+ will have a total of 20-2= 18 electrons.
(a) 8 (b) 9 (c) 10 (d) 11 Solution: Option (c) is the answer. Because the number of electrons equals the number of protons, X2- will contain 8+2 electrons = 10 electrons.
(a) Lead ion battery (b) Sodium-ion battery (c) Hydrogen ion battery (d) Lithium-ion battery Solution: Option (d) is the answer. A lithium-ion (Li-ion) battery is a high-performance battery that...
(a) Lithium chloride (b) Ammonium chloride (c) Calcium chloride (d) Carbon tetrachloride Solution: Option (d) is the answer. Carbon tetrachloride is a covalent compound that dissolves in...
(a) High melting point (b) Low melting point (c) Occurrence as solid (d) Conduction of electricity in the molten state. Solution: Option (b) is the answer. Because it is created by the gain of...
(a) KCl and HCl (b) HCl and CCl4 (c) CCl4 and NaCl (d) KCl and CCl4 Solution: Option (b) is the answer. Covalent bonding is found in non-ionic substances. Because two atoms share a pair of...
(a) Y3- (b) Y2+ (c) Y2- (d) Y3+ Solution: Option (d) is the answer. Explanation: Because one atom of the element Y contains 20 protons, the number of electrons will be the same. Its ion Y2+ will...
(a) X2- (b) X3+ (c) Y2- (d) X– Solution: Option (c) is the answer. Explanation: An element X has an atomic number of 16 (2,8,6). As a result, it requires two electrons to complete its octet. As a...
(a) 8 only (b) 2 only (c) 8 or 2 (d) 8 or 4 Solution: Option (c) is the answer. Helium is the only noble gas with a valence shell with two electrons. The valence shells of other noble gases have...
(a) Solubility in water (b) Electrical conductivity in solid-state (c) High melting and boiling points (d) Electrical conductivity in molten state Solution: Option (b) is the answer. Because of the...
X: 2,8 Y: 2,8,7 Z: 2,8,2 Which of the following is correct regarding these elements? Solution: (a) X is a metal (b) Y is a metal (c) Z is a non-metal (d) Y is a non-metal and Z is a metal Solution:...
(a) NaCl (b) CCl4 (c) MgCl2 (d) CaCl2 Solution: Option (b) because it is a covalent compound and they don't conduct electricity. The molecule carbon tetrachloride, or CCl4, is symmetrical, with four...
(a) P and R (b) Q and S (c) P and S (d) R and S Solution: Option (c) is the answer because the atomic numbers of the four elements P, Q, R, and S are 6,10, 12, and 17 respectively. P (6= 2,4) and S...
(a) A and D (b) B and C (c) A and C (d) B and D Solution: Option (d) is the answer. Explanation: The atomic numbers of the four elements A, B, C, and D, respectively, are 6, 8, 10, and 12. B (8=...
(a) 17 (b) 18 (c) 19 (d) 20 Solution: Option (b) is the answer. The element Y has an atomic number of 17. As 1 electron is added to its Y–, the total number of electrons in the Y– will be...
(a) 18 (b) 19 (c) 20 (d) 21 Solution: Option (a) is the answer. To achieve a stable electronic state, element X will lose one of its valence electrons, resulting in the formation of a positive...
(e) Why are covalent compounds generally poor conductors of electricity? (d) Because magnesium chloride is an ionic substance, it will conduct electricity. It conducts electricity because it...