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CBSE Questions for Class 8 Chemistry Materials Metals And Non Metals Quiz 5 - MCQExams.com
CBSE
Class 8 Chemistry
Materials Metals And Non Metals
Quiz 5
Which of the following non-metal is commonly used as pesticides and photography?
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Bromine
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Helium
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Selenium
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Iodine
Explanation
Bromine compounds are effective pesticides, used
to prevent pests from attacking stored grain and other produce. Bromine compounds are also used in photography. Several compounds are used to make the light-sensitive component of a photographic emulsion, without bromine compounds photographs would not capture sufficient light.
Which of the following non-metal is a good conductor of electricity?
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Sulphur
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Phosphorus
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Nitrogen
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Graphite
Why is sodium stored in kerosene?
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It sublimates if kept in open.
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It is highly reactive and burns in air.
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To protect it from rusting.
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None of the above
Explanation
Sodium metal is very reactive. It reacts vigorously with oxygen and water. A lot of heat is generated in this reaction. Hence, it can react with water vapour and oxygen present in the air. Thus, it is stored in kerosene to avoid this violent reaction.
Mark the correct statement.
a) Metals lose their lustre on keeping in air.
b) Gold is lustrous.
c) Metals are lustrous and can be polished.
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a, b are correct
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b, c
are correct
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a, c
are correct
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All the statements are correct
Explanation
Metals lose their lustre when kept exposed to air for a long time and get a dull appearance.
Gold is known for its lustrous yellow appearance.
Lustre is a property of metals and metals can be polished to increase their metallic lustre.
Hence, all the statements are correct.
Non-metals do not have lustre which means:
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they do not have a shining surface
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they can't produce sound
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they can't conduct heat
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None of the above
Explanation
Non-metals do not have lustre which means that non-metals do not have a shining surface. Thus they show a dull appearance.
Which of the following metals were used as money in ancient times?
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Gold
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Copper
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Iron
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All of the above
Explanation
Silver, copper, and iron were used as currency in the olden days.
Gold, copper, and silver in ancient times were used as money in order to allow people to trade, that is, exchange goods and services over long distances.
If we dip a piece of aluminium foil in sodium hydroxide:
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iron hydroxide and sodium metal will be formed
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hydrogen gas is liberated
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no reaction takes place
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temperature needs to be defined
Explanation
Aluminium reacts with sodium hydroxide base to liberate hydrogen gas.
Metals used to make bullet proof alloy steels is:
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Titanium
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Zirconium
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Magnetite
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Silicon
Explanation
Metals used to make bullet proof alloy steel is $$Titanium.$$
Identify the non-lustrous element.
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Bromine
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Iodine
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Silver
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Iron
Explanation
Iodine has a lustrous appearance.
Bromine is a non-metal so it is non-lustrous. Silver and iron are metals and they are lustrous.
Iodine is a non-metallic, dark-gray/purple-black, lustrous, solid element. It is non –metal and hence lustrous.
Which of the following is/are use(s) of aluminium?
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It is used in paints.
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It is used for packaging.
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It is used to make electrical wires.
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All of the above
Explanation
The uses of aluminium are:
It is used in paints
It is used for packing food
It is used to make electrical wires
Which was the first metal used by humans?
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Iron
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Copper
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Zinc
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Gold
Explanation
Metals were discovered and starts using approximately
5000
years ago. First metal to be used was the copper. Then after silver and gold. These metals were found in free state in nature.
The metal which is silvery light, malleable and ductile, and the boiling point is around $$2500^\circ C$$ is:
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zinc
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iron
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aluminium
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tin
Explanation
The metal which is silvery light, malleable and ductile and the boiling point is around
$$2500 ^\circ C$$ is $$\text{aluminium}$$.
Which of the following is not used in making cooking utensils even though it is a metal?
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Copper
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Lead
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Silver
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Iron
Explanation
Lead is a poor conductor of heat. Also, it is a poisonous metal. So, it can't be used to make cooking utensils.
Number of -ve charges on an ion formed by a non-metal is:
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Equal to number of valence electrons minus eight
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Equal to the period
of the non-metal
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Equal to the group number of the non-metal
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Equal to the group number of the non-metal minus five
Explanation
Non-metal gains electron to form anion and acquire negative charge on it.
For example: $$O + 2e^- \longrightarrow O^{2-}$$
Oxygen atom gains 2 electrons to form anion and acquire 2 negative charge on it which is equal to number of valence electrons of Oxygen atom i.e. $$6 - 8 = 2$$
Solutions of copper sulphate, iron sulphate and zinc sulphate are prepared and marked I, II and III respectively. Few pieces of aluminium are added to each solution. After some time a change will be observed in:
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I and II
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II and III
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III and I
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All of the above
Explanation
This type of comparison can be done by looking at the position of metals in the reactivity series.
In this series, the metals at the top are more reactive
so there will be a displacement reaction.
It is a chemical reaction
in which a more reactive element displaces a less reactive element from its compound.
Here we can see that Aluminium is on the top of zinc, iron, and copper,
so it will displace all of them from their salt
and it will form a salt of aluminium in the solution.
The reaction between the solutions of copper sulphate, iron sulphate and zinc sulphate and Aluminium are given below:
$$I.\ 2Al + 3CuSO_{4} \rightarrow 3Cu + Al_{2}(SO_{4})_{3}$$
$$II.\ 2Al + 3FeSO_{4} \rightarrow 3Fe + Al_{2} (SO_{4})_{3}$$
$$III.\ 2Al + 3ZnSO_{4} \rightarrow 3Zn + Al_{2}(SO_{4})_{3}$$
When metals reacts with base, the product obtained is_____ and ______gas.
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salt, hydrogen
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salt, carbon dioxide
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water, hydrogen
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salt, oxygen
Gold reacts with base to produce salt and hydrogen.
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True
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False
Explanation
$$\text{False}$$
All the metals do not react with the base. Only a few metals like lead, tin, aluminium, and zinc react with bases. Gold is resistant to acids and bases. Hence it does not react with the base to produce salt and hydrogen.
Thus the above statement is $$\text{false}$$.
Which of the following statements is correct?
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All metals are ductile.
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All non-metals are ductile.
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Generally, metals are ductile.
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Some non-metals are ductile.
Explanation
Metals are generally malleable — that is, they can be hammered or pressed permanently out of shape without breaking or cracking — as well as fusible (able to be fused or melted) and ductile (able to be drawn out into a thin wire).
Typically they are malleable and ductile, deforming under stress without cleaving. However, there are some metals which are not ductile.
For example, sodium and mercury.
Non-metals on the other hand are not ductile.
Which of the following element is sonorous?
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Hydrogen
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Sulphur
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Iron
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All of above
Explanation
Sonority means making a sound. It is a characteristic property of a metal. Iron being a metal is sonorous whereas hydrogen and sulphur are non-metals.
So, the correct option is $$C$$
Which of the following metal is used in atomic energy and space projects?
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Titanium
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Zirconium
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Sodium
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All of above
Explanation
Titanium, sodium and zirconium metals are used in atomic energy and space science projects.
Zirconium is used in:
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poison ivy lotion
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sand papers
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ceramics
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all of above
Explanation
Zirconium $$(Zr)$$ slightly resembles Titanium $$(Ti)$$ in poison case. it is also used as a poison. It is used in making sandpaper and ceramics.
Zirconium is the main element in cubic zirconia, which has the formula $$ZrO_2$$. Also, zirconium carbonate $$(ZrCO_3)$$ binds to urushiol, the active ingredient in poison ivy oil.
Tungsten filament is:
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non-polar covalent substance
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polar covalent substance
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ionic substance
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metallic substance
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noble gas
Explanation
Tungsten filament represents metallic substance.
Tungsten is a metal. Other examples of metals include iron, copper, aluminium, magnesium, sodium, lead, zinc etc.
Drawing of ductile metals into thin wires results in:
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increase in molecular separation
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increase in stress in the metal
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reduction of cross-sectional area
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all of these
Explanation
On application of tensile forces to a ductile material displaces the molecules, and hence increases in molecular separation which results in an increase in the stress level inside the metal. This process also results in increase in length and a decrease in the cross-sectional area of the metal.
Which of the following can be drawn into thin wires?
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$$Br$$
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$$Al$$
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$$Cl$$
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$$O$$
Explanation
Metals can be drawn into thin wires. Aluminium is a metal among the given elements and it has ductility.
Aluminium foil used for wrapping____
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food
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clothes
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plastic
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wires
Explanation
Aluminum is a metal. Metals are malleable and ductile, and they can be drawn into thin sheets, and wires respectively. As aluminum is malleable, thin foil can be made out of it. These foils have the property to keep the food warm. Hence, it is used for wrapping food.
A manufacturer has to produce wires made of different varieties of metals. Which among the following metal cannot be taken into consideration for this purpose?
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Gold
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Silver
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Aluminium
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Zinc
Explanation
Zinc is an exception among metals and does not show ductility and low thermal and electrical conductivity.
Which is the correct statement regarding malleability?
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Malleability is the physical property of non-metals
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Malleability is the chemical property of metals
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Malleability is the physical property of metals
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Malleability is the chemical property of non-metals
Explanation
Malleability is a physical property of metals. A malleable material can be flattened into thin sheets by hammering or rolling. Solid metal can bend or be hammered into other shapes without breaking.
Hence, the correct option is $$C$$
Which of the following statements are correct?
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All metals are ductile
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All non metals are ductile
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Generally metals are ductile
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Some metals are ductile
Explanation
The property by the virtue of which metals can be drawn into thin wires is called ductility. Generally, metals are ductile. For example, copper.
Non-metals are non-ductile as they cannot be drawn into wires.
Apart from most metals, which of these materials can show ductility?
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Plastics
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Alloys
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Chewing gums
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All of these
Explanation
Some plastics and some alloys have the property of getting drawn into wires. Chewing gum is also very flexible and shows ductility.
Nature of oxides of non-metal is :
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Acidic
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Basic
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Amphoteric
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Neutral
Explanation
The oxides of non-metal are acidic in nature as oxide of non-metal reacts with water to form acid.
Example :
$$CO_2 + H_2O \rightarrow H_2CO_3$$
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