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CBSE Questions for Class 8 Chemistry Materials Metals And Non Metals Quiz 2 - MCQExams.com
CBSE
Class 8 Chemistry
Materials Metals And Non Metals
Quiz 2
Calcium phosphate is present in tooth enamel. Its nature is __________.
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basic
0%
acidic
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neutral
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amphoteric
Explanation
Tooth enamel is one of the four major tissues that make up the tooth in humans and many other animals. It makes up the visible part of the tooth covering the crown. The other major tissues are dentin, cementum and dental pulp. It protects the teeth but can be easily decayed and destroyed. It is the hardest substance in the human body and contains the highest percentage of minerals 96% . This mineral is hydroxyapetite which is crystalline calcium phosphate. In humans enamel varies in thickness over the surface of the tooth thickest at the cusps and thinnest at the border.
$${ Ca }_{ 10 }{ (PO }_{ 4 })_{ 6 }{ (OH) }_{ 2 }\left( s \right) +8{ H }^{ + }\left( aq \right) \rightarrow 10{ Ca }^{ 2+ }\left( aq \right) +6{ HPO }_{ 4 }^{ 2- }\left( aq \right) +2{ H }_{ 2 }O\left( l \right)$$
Which one of the following nutrient is not available in fertilizers?
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Nitrogen
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Phosphorus
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Iron
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Potassium
Explanation
Potassium, Nitrogen, and Phosphorous are normally derived from the soil in the form of inorganic salts and are nutrients available in fertilizers that make up
0.5 to 6.0 percent. Hence iron is a
nutrient that is not available in fertilizers.
Materials which can be drawn into wires are called ductile. Which of the following is not used as a ductile material?
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Silver
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Copper
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Sulphur
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Aluminium
Explanation
Silver is a soft metal with high thermal and electrical conductivity. It is malleable and ductile similar to gold. However, silver content in ores mines in India is about 1% obtained as a by-product in the mining of gold and lead. Thus, silver is highly expensive to be drawn into wires for the industries.
Which of the following is used for dissolution of gold?
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Hydrochloric acid
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Sulphuric acid
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Nitric acid
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Aqua regia
Explanation
Aqua regia is a chemical solution that is obtained by mixing one part nitric acid and three parts hydrochloric acid. It can dissolve gold, platinum, titanium, and other noble metals.
Metal that exists in the liquid state at room temperature is :
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Mercury
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Silver
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Palladium
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Platinum
Explanation
Mercury is a metal which is liquid at room temperature.
An element $$A$$ is soft and can be cut with a knife. This is very reactive with air and cannot be kept open in the air. It reacts vigorously with water. The element $$A$$ is:
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Magnesium
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Sodium
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Gold
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Calcium
Explanation
Sodium is so soft that it can be cut with a knife. It reacts vigorously with oxygen when kept open in the air and hence, we keep it immersed in kerosene oil. It also reacts vigorously with water.
Boojho has learned that non-metals on beating with a hammer are generally broken into pieces. Which of the following can be broken into pieces?
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Iron nail
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Aluminium wire
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Copper plate
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Piece of coal
Explanation
Malleability is the property by which a substance can be converted into sheets by beating with a hammer.
$$\bullet$$ Iron, aluminum, and copper are metals and therefore are malleable.
$$\bullet$$ Carbon is a nonmetal and is neither malleable nor ductile.
Coal is a form of carbon and is non-metal. If it is beaten by a hammer, it will break into pieces.
Magnesium ribbon on burning in air produces:
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magnesium oxide, water and light
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magnesium oxide and heat
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magnesium oxide, heat and light
0%
magnesium oxide, water and heat
Explanation
When a piece of magnesium ribbon is ignited, light and heat are produced.
Magnesium reacts with oxygen to form a compound called magnesium oxide.
The reaction is as follows:
$$2Mg + O_2 \rightarrow 2MgO + \text{heat} + \text{light}$$
Hence, the correct option is $$\text{C}$$
Which of the following observations most strongly suggest that a solid element X is a non- metal?
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X forms an acidic oxide.
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X has a high melting point
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X is a conductor of electricity.
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X reacts vigorously with chlorine.
Which of the following non-metals react and catches fire on exposure to air?
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Phosphorus
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Nitrogen
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Sulphur
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Hydrogen
Explanation
Phosphorus is a very reactive non-metal. It catches fire if exposed to air.
Option A is correct.
Soft metal(s) which can be cut with a knife is(are) :
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Lithium
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Potassium
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Sodium
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A, B and C
Explanation
Metals, such as Lithium, Sodium and Potassium can be cut with a knife as they are very soft compared to other metals.
Generally, metallic oxides are basic and non-metallic oxides are acidic in nature. Solution of which of the following oxides in water will change the colour of blue litmus to red?
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Sulphur dioxide
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Magnesium oxide
0%
Iron oxide
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Copper oxide
Explanation
The oxides of metal are basic in nature or in other words they react with acids to form salt and water. In the case of non-metals, they are acidic in nature and form acids when they dissolve in water.
When sulphur
dioxide is dissolved in water sulphurous,
acid is formed. The reaction can be given
as follows:
$$SO_2 + H_2O \rightarrow H_2SO_3$$
The sulphurous acid turns blue
litmus paper red.
Paheli prepared a blue coloured solution of copper sulphate in beaker A and placed an iron nail in it. Boojho prepared a yellowish green solution of ferrous sulphate in beaker B and placed a copper wire in it. Changes they observe in the two beakers after an hour will be :
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in beaker A, no change ; in beaker B, change to green
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in beaker A, no change ; in beaker B, no change
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in beaker A, changes to green ; in beaker B, no change
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in beaker A, changes to green ; in beaker B, change to blue
Explanation
Fe displaces the Cu from $$CuSO_{4}$$ solution in beaker A as Fe is more reactive than Cu.
Therefore the blue colour of the solution changes to green due to the formation of $$FeSO_{4}$$.
In beaker B, no reaction takes place as $$Cu$$ being less reactive cannot displace $$Fe$$ from $$FeSO_{4}$$ solution.
Hence the correct option is C.
Non-metals which are present in fertilizers and enhance the growth of plants is:
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nitrogen
0%
phosphorus
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potassium
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both $$A$$ and $$B$$
Explanation
Non-metals which are present in fertilizers and enhance the growth of plants are nitrogen and phosphorus. Potassium is a metal. It is also present in fertilizers.
Sulphur is a poor conductor of electricity.
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True
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False
Explanation
Sulfur is a non-metal and its property is consistent with that of other non-metals, that's why it does not conduct electricity.
Which of the following are properties of non-metals?
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Lustre
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Can form alloys
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Amorphous
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Non-conductive towards electricity
Explanation
The properties of non-metals are:
They are amorphous.
They are not malleable and ductile.
They are poor conductors of heat and electricity.
They do not form alloys.
A student added zinc granules to copper sulphate solution taken in a test tube. Out of the following, the correct observation (s) made by the student will be:
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zinc granules have no regular shape
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zinc granules are silvery grey coloured
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colour of zinc granules changed to brownish black
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$$CuSO_{4}$$ change into $$ZnSO_{4}$$
Explanation
A student added zinc granules to copper sulphate solution taken in a test tube. The correct observations made by the student will be:
(A) zinc granules have no regular shape.
(B) zinc granules are silvery-grey colored.
(C) colour of zinc granules changed to brownish-black due to chemical change.
(D) $$\displaystyle CuSO_4$$ change into $$\displaystyle ZnSO_4 $$ due to the following chemical change.
$$\displaystyle CuSO_4 + Zn \rightarrow ZnSO_4+Cu \downarrow$$
Which of the following is an insulator?
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Copper
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Iron
0%
Sulphur
0%
Graphite
Explanation
Unlike metals which have a 'sea' of free electrons that can be used to conduct electricity, Sulphur is an insulator.
Copper and iron being metals conduct electricity due to the presence of free electrons.
Graphite conducts electricity due to the motion of non bonded electrons between its adjacent layers.
State true or false.
Diamond and iodine are non-metals which are lustrous.
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True
0%
False
Explanation
Metal or non-metal is said to be lustrous when it has a shiny appearance.
Generally, metals show this property.
Diamond and iodine being non-metals show this property because of their crystal structure.
Therefore, option A is correct.
A non-metallic oxide dissolves in water to give :
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alkali
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acid
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base
0%
none of these
Explanation
Non metallic oxide dissolves in water to form an acid.
$$CO_2+{ H }_{ 2 }O\rightarrow { H }_{ 2 }{ CO }_{ 3 }$$
Carbonic acid is an acid formed by reaction of water with oxide of carbon.
Metals can be hammered into thin sheets. This property is called:
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density
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malleability
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ductility
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strength
Explanation
The ability to be hammered, pressed, or rolled into thin sheets without breaking is called malleability. Metals are generally malleable.
Which of the following elements produce basic oxides upon reacting with oxygen?
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Chorium
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Sulphur
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Sodium
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Magnesium
Explanation
Metals react with oxygen to produce basic oxides.
Sodium and magnesium metal react with the oxygen of the air at room temperature to form sodium oxide and magnesium oxide respectively. These oxides react with water to form hydroxides.
$$4Na + O_2 \rightarrow 2Na_2O$$
$$Na_2O + H_2O \rightarrow 2NaOH$$
$$2Mg + O_2 \rightarrow 2MgO$$
$$MgO + H_2O \rightarrow Mg(OH)_2$$
The oxide of sodium is _______ in nature.
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acidic
0%
basic
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amphoteric
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none of these
Explanation
Oxide of sodium is strongly basic due to the presence of $$O^{-2}$$ which is a strong base with high tendency to combine with hydrogen ion.
Which of the following is liquid at ordinary temperature ?
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Germanium
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Gallium
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Gold
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Galena
Explanation
Gallium is liquid at ordinary temperature.
An alloy which is sonorous is:
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duralumin
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bell metal
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type metal
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gun metal
Explanation
A sonorous alloy is bell metal.
Bell metal (copper, tin)
Type metal (lead, tin, antimony)
Duralumin (copper, aluminum)
Gunmetal (Copper, Tin, zinc)
Compound can be reduced to copper when heated with coke is
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Copper hydroxide
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Copper oxide
0%
Copper sulphide
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All of these
Explanation
The metals, which are low in the reactive series, undergo reduction reaction. Their metal oxides react with carbon to reduce the metal oxide to its metal and form an oxide of carbon.
$$2CuO+C \rightarrow 2Cu+CO_2$$
Which of the following statements is correct about the physical properties of metals and non-metals?
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Both are sonorous.
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Both are poor conductors of heat.
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Most metals are hard and lustrous, while most non-metals are soft and dull.
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Metals do not conduct electricity while non-metals do.
Explanation
Metals are generally sonorous, and good conductors of heat and electricity. On the other hand, most non-metals are not sonorous and are bad conductors of heat and electricity.
Moreover, metals are generally hard and lustrous, and non-metals are soft and dull.
Examples of metals include iron, copper, aluminium. Examples of non-metals are carbon, oxygen, phosphorus.
X is an element in the form of a powder. X burns in oxygen and the product is soluble in water. The solution is tested with litmus.
If X is a non metal, then the litmus will turn:
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Red to blue
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Blue to red
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No change on red litmus
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Both $$B$$ and $$C$$
Explanation
If "X" is non-metal then its oxide is acidic and when dissolved in water gives acid.
We know acids turn blue litmus red.
So, the blue litmus will turn red while the red litmus remains the same.
So, Option (D) is correct.
Compare the properties of a typical metal and a non-metal on the basis of the following.
Conductivity of heat and electricity:
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Metals are good conductor of heat and electricity.
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Non metals are good conductor of heat and electricity.
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Metals are bad conductor of heat and electricity.
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Both B and C
Explanation
Metals have free electrons which can conduct heat and electricity,
So, metals are good conductor of heat and electricity.
A student takes Cu, Al, Fe and Zn strips separately in four test-tubes labelled as I, II, III and IV respectively. He adds 10 ml of freshly prepared ferrous sulphate solution to each test-tube and observes the colour of the metal in each case. He would observe a black residue in:
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I and II
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I and III
0%
II and III
0%
II and IV
Explanation
The black residue will appear due to the formation of iron in tubes (II) and (IV) because of displacement reaction taking place and the reaction is given below
$$2Al(s) + 3FeSO_4(aq) \rightarrow Al_2(SO_4)_3(aq) + 3Fe(s)$$ (Black residue)
$$Zn(s) + FeSO_4(aq) \rightarrow ZnSO_4(aq) +Fe(s) $$ (Black residue)
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