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Chemistry [2 Mark Question Answer]

Metallurgy · ICSE STD 10 (ICSE - English Medium). 27 questions.

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[2 Mark Question Answer]

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27 questions · timed · auto-graded

Question 12 Marks
State the property of the metal being utilized in the following :
Use of metalProperty
Zinc in Galvanization
Aluminium in Thermite welding
Answer
Use of metalProperty
Zinc in galvanisationZinc oxidises more readily than iron, thus preventing the rusting of iron.
Aluminium in thermite weldingAluminium is a good reducing agent.
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Question 22 Marks
state two properties of brass that render it more useful for some purpose than its components?
Answer
Two properties of brass that make it more useful than its components are:
(i) It is malleable and ductile.
(ii) It resists corrosion.
(iii) Can be easily cast.
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Question 32 Marks
What is an amalgam? State its use with an example ?
Answer
A mixture or an alloy of mercury with a number of metals or an alloy such as sodium, zinc, gold and silver as well as with some non-metals is known as amalgam.
Dental amalgam is a mixture of mercury and a silver tin alloy.
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Question 42 Marks
Explain the following :
zinc is used to cover iron so as to prevent rusting of iron. why?
Answer
Zinc is electropositive metal than iron, gets oxidized and saves iron. Also, zinc forms a protective layer of ZnO on iron. This layer is sticky and impervious in nature and protects the iron metal underneath from rusting.
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Question 52 Marks
Explain with reason:
A neutral gas other than oxygen is formed at the anode during electrolysis of fused alumina.
Answer
An anode is made of carbon which gets oxidised in the presence of oxygen to form carbon monoxide which is a neutral gas.
$
2 C + O _2 \rightarrow 2 CO
$
An anode is made of carbon which gets oxidised in the presence of oxygen to form carbon monoxide which is a neutral gas.
$
2 C + O _2 \rightarrow 2 CO
$
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Question 62 Marks
Electrolytic reduction is done to obtain aluminium?
Answer
As aluminium has great affinity for oxygen, so it is stable compound. It is not easily reduced by common reducing agents like carbon, carbon monoxide or hydrogen. Hence, electrolytic reduction is chosen as the method for reducing alumina.
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Question 72 Marks
Carbon can reduce lead oxide but not aluminium oxide ?
Answer
Aluminium has a great affinity towards oxygen and so cannot be reduced by carbon or carbon monoxide or hydrogen whereas lead oxide can be easily reduced to metal lead by carbon.
$
PbO + C \longrightarrow Pb + CO
$
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Question 82 Marks
Explain with reason:
Roasting is carried out on sulphide ores and not on carbonate ores?
Answer
Roasting provides oxygen to convert metallic sulphides into metallic oxide and $SO _2$ which takes place when heated in excess of air. Carbonate is converted into oxide by loss of $CO _2$ which takes place in the absence of air and when heated strongly.
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Question 92 Marks
Explain with reason:
In the electrolytic reduction of alumina, the graphite anode is gradually consumed.
Or
Why the anode has to be replaced from time to time in this process?
Answer
In the electrolytic reduction of alumina, the graphite (anode) is oxidized by oxygen to $C O$ and further forms $CO _2$, so it is consumed and has to be replaced from time to time.
$2 C + O _2 \longrightarrow 2 CO $
$2 CO + O _2 \longrightarrow 2 CO _2$
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Question 102 Marks
In order to obtain 1 tonne of aluminium the following inputs are required. 4 tonnes of bauxite, 150 kg of sodium hydroxide and 600 kg of graphite. The aluminium compound in bauxite is aluminium oxide and the main impurity is iron (III) oxide, Aluminium is obtained by the electrolysis of aluminium oxide dissolved in cryolite
(i) Name the process used for the purification of bauxite
(ii) Write the equation for the action of heat on aluminium hydroxide
Answer
  1. The process used for the purification of bauxite is Baeyer's process.
  2. Action of heat on aluminium hydroxide:

$\ce{2Al(OH)3 ->[heat][1000°C]Al2O3 + 3H2O}$

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Question 112 Marks
In order to obtain 1 tonne of aluminium the following inputs are required. 4 tonnes of bauxite, 150 kg of sodium hydroxide and 600 kg of graphite. The aluminium compound in bauxite is aluminium oxide and the main impurity is iron (III) oxide, Aluminium is obtained by the electrolysis of aluminium oxide dissolved in cryolite
♦ when bauxite is treated with sodium hydroxide solution, what happens to
(i) the aluminium oxide
(ii) the iron (III) oxide
Answer
(i) The aluminium oxide forms sodium aluminate.
$
Al _2 O _3 \cdot 2 H _2 O +2 NaOH \xrightarrow{150^{\circ} C -200^{\circ} C } 2 NaAlO _2+3 H _2 O
$
(ii) The iron(III) oxide does not dissolve in $NaOH$ and is removed by filtration.
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Question 122 Marks
What is red mud, how is it removed?
Answer
  • Red mud, also known as bauxite residue, is an industrial waste generated during the refinement of bauxite into alumina using the Bayer process. It is composed of various oxide compounds, including the iron oxides which give its red color.
  • Red mud consists of ferric oxide, sand, etc. left after bauxite dissolves in NaOH forming sodium aluminate and is removed by filtration.
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Question 132 Marks
Explain and give reasons why aluminium vessels should not be cleaned with powders containing alkalis ?
Answer
Aluminium vessels should not be cleaned with powders containing alkalis because aluminium reacts with alkalis to produce meta aluminate.
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Question 142 Marks
Aluminium is a more active metal than iron, but suffers less corrosion. Why?
Answer
When aluminium is exposed to the atmospheric air, it combines with oxygen and a film of aluminium oxide $(Al_2O_3)$ is formed at the surface. This hard, tightly adhering film of aluminium oxide prevents corrosion.
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Question 152 Marks
How are the following metallic oxides reduced? Write equations:
Iron (ll) oxide
Answer
Iron(II) oxide:
$4 FeO + O _2 \longrightarrow 2 Fe _2 O _3 $
$Fe _2 O _3+3 CO \xrightarrow{600^{\circ} C -400^{\circ} C } 2 Fe +3 CO _2$
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Question 162 Marks
How is concentrated ore changed to oxide?
Answer
Concentrated ore is changed into oxide by heating ZnS in excess of air.
$
2 ZnS +3 O _2 \xrightarrow{800^{\circ} C } 2 ZnO +2 SO _2
$
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Question 172 Marks
What do you observe when hydrogen is passed over heated copper oxide?
Answer
Black copper oxide is reduced to brown/red.
$
CuO + H _2 \xrightarrow{\Delta} Cu + H _2 O
$
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Question 182 Marks
Name : The processes involved in (i) dressing of the ores (ii) refining of ores .
Answer
(i) Processes involved in Refining of ores are:
1. Distillation
2. Liquation
3. Oxidation
4. Electro-refining
(ii) crushing and grinding
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Question 192 Marks
State three objectives achieved during the roasting of ores.
Answer
  1. It removes moisture from the ore.
  2. It expels oxide.
  3. It oxidises sulphide ores to oxide ores.
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Question 202 Marks
name the methods used for purification ?
Answer
Methods used for purification are:
1. Distillation
2. Liquation
3. Oxidation
4. Electro-refining
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Question 212 Marks
on which factors does purification of metals depend?
Answer
The purification depends upon:
1. Nature of metal.
2. Nature of impurities present in the metal.
3. Purpose for which metal is to be used
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Question 222 Marks
Give equation for the reduction of Zinc oxide
Answer
Reduction of zinc oxide:
$
ZnO + C \xrightarrow{1400^{\circ} C } Zn + CO
$
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Question 232 Marks
Define roasting. Name an ore on which roasting is done. Give balanced equation.
Answer
Roasting is the process of heating concentrated ore to a high temperature in the presence of air. The ore zinc blende is roasted in order to get zinc oxide.
Example: Zinc sulphides are oxidised to zinc oxide.
$
2 ZnS +3 O _2 \longrightarrow 2 ZnO +2 SO _2
$
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Question 242 Marks
Name the three classes in which elements are classified. Which was the first metal used by man?
Answer
Three classes in which elements are classified are :
Metals , Non-metals and Metalloids
Copper was the first metal used by man.
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Question 252 Marks
Distinguish between:
an ore and a metallic compound
Answer
Ores are those minerals from which the metals are extracted commercially at low cost and with minimum effort. A metallic compound is a compound that contains one or more metal elements. Examples: AgNO3 - Silver nitrate is a metallic compound.
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Question 262 Marks
Distinguish between:
a mineral and an ore
Answer
Minerals are naturally occurring compounds of metals which are generally present with other matter such as soil, sand, limestone and rocks. Ores are those minerals from which the metals are extracted commercially at low cost and comfortably. All ores are minerals, but all minerals are not necessarily ores.
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Question 272 Marks
Read the passage below and answer the following questions:
Electrolytic reduction is a type of electrolysis in which an electric current is passed through a molten or dissolved ionic substance, generating chemical reactions between the electrodes and the decomposition of the components. Electrolytic reduction is used to produce certain metals such as K , Na, and Al . The electrolytic reduction can be made in a molten state only. Alumina melts at higher temperature, so it is not easy to collect it. This difficulty was removed by adding cryolite to alumina as a solvent to obtain the globules of aluminium.

 Q.1. Aluminium melts at what temperature?
(a) $1280^{\circ} C$    (b) $2050^{\circ} C$    (c) $2040^{\circ} C$    (d) $1850^{\circ} C$
 Q.2. Which scientist revolutionised the aluminium industry?
(a) Heroult    (b) Baeyer    (c) Hoope    (d) Hall
Answer
1. B. $2050^{\circ} C$
Explanation: Aluminium is a strong metal and has a high melting point of $2050^{\circ} C$.
2. D. Hall
Explanation: Hall worked in the development of aluminium extraction.
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[2 Mark Question Answer] - Chemistry STD 10 Questions - Vidyadip