chapter one important one mark questions

Download Tamil Nadu 12th Standard Chemistry question papers, model tests, one-mark questions, important questions, and public exam papers in PDF format. Free study materials and answer keys for TN State Board students.

Questions:

Multiple Choice Question

5 x 1 = 5

Which of the metal is extracted by Hall-Heroult process?

(a)

(b)

(c)

(d)

The metal oxide which cannot be reduced to metal by carbon is ________.

(a)

PbO

(b)

Al₂O₃

(c)

ZnO

(d)

FeO

Which one of the following reaction represents calcinations?

(a)

\(2Zn+{ O }_{ 2 }\rightarrow 2ZnO\)

(b)

\(2ZnS+3O_{ 2 }\rightarrow 2ZnO+2SO_{ 2 }\)

(c)

\(MgCO_{ 3 }\rightarrow MgO+CO_{ 2 }\)

(d)

Both (a) and (c)

Roasting of sulphide ore gives the gas (A).(A) is a colourless gas. Aqueous solution of (A) is acidic. The gas (A) is______.

(a)

CO₂

(b)

SO₃

(c)

SO₂

(d)

H₂S

Bauxite has the composition ______.

(a)

Al₂O₃

(b)

Al₂O₃.nH₂O

(c)

Fe₂O₃.2H₂O

(d)

None of these

Generic 2

3 x 2 = 6

Write a short note on hydroboration.

Give the structure of CO and CO₂.

Write a note on Fisher tropsch synthesis.

Generic 3

3 x 3 = 9

Mention the uses of CO₂.

10.

What is burnt alum?

11.

Give the uses of silicones.

Assertion and reason

5 x 2 = 10

12.

Assertion: Calamine and Dolomite are the Carbonate ores.
Reason: Calamine is ZnCO₃ whereas dolomite is MgCO₃.ZnCO₃.
Codes:
a) Both assertion and reason are true and the reason is the correct explanation of the assertion.
b) Both assertion and reason are true but the reason is not the correct explanation of the assertion.
c) Assertion is true, but reason is false.
d) Both assertion and reason are false

13.

Assertion: Cuprite is concentrated by froth flotation process.
Reason: Cuprite is the sulphide ore
Codes:
a) Both assertion and reason are true and the reason is the correct explanation of the assertion.
b) Both assertion and reason are true but the reason is not the correct explanation of the assertion.
c) Assertion is true, but reason is false.
d) Both assertion and reason are false

14.

Assertion: Zone refining is carried out in an inert gas atmosphere
Reason: The metal is treated with a suitable reagent which can form a volatile compound with the metal.
Codes:
a) Both (A) and (R) are true and (R) is the correct explanation of (A).
b) Both (A) and (R) are true and (R) is not the correct explanation of (A).
c) (A) true but (R) false.
d) Both (A) and (R) are false

15.

Assertion: Metallic zinc is used in galvanising metals such as iron and steel.
Reason: Zinc is also used to produce die castings
Codes:
a) Both (A) and (R) are true and (R) is the correct explanation of (A).
b) Both (A) and (R) are true and (R) is not the correct explanation of (A).
c) (A) true but (R) false.
d) Both (A) and (R) are false.

16.

Assertion: Aluminium is used in the design of chemical reactors, medical equipments, refrigeration units and gas pipelines.
Reason: Aluminium shows high resistance to corrosion
Codes:
a) Both (A) and (R) are true and (R) is the correct explanation of (A)
b) Both (A) and (R) are true and (R) is not the correct explanation of (A).
c) (A) true but (R) false
d) Both (A) and (R) are false.

One or Two Words / Correct Statement

5 x 1 = 5

17.

I. Ores are associated with non-metallic impurities
II. Ores are associated with rocky materials
III. Removal of impurities is known as concentration of ore.
IV. Ellingham diagram shows the stability of different metal oxides.
a) I, II, III & IV b
b) Only II
c) Only I
d) III & IV

18.

I. Froth flotation is used to concentrate sulphide ores.
II. Magnetic separation is applicable for ferromagnetic ores.
III. Roasting method used to sulphide ores to oxides
IV. Magnetic separation is used to concentrate heavy oxide ores.
a) III & IV
b) Only II
c) Only I
d) I, II & III

19.

I. Ellingham diagram helps to select a suitable reducing agent.
II. Magnesite is calcinated to obtain magnesia.
III. Calcination is a process of cooling substances.
IV. Sulphur dioxide is harmful to the environment.
a) I, II & IV
b) Only II
c) Only I
d) III & IV

20.

I. Copper is the first metal used by the human
II. Aluminium is used in galvanising metals
III. Aluminium is a good conductor of electricity
IV. Magnets can be made from iron.
a) Only I
b) Only II
c) I, III & IV
d) III & IV

21.

I. All ores are minerals.
II. All minerals are not ores.
III. Aluminium can be extracted from bauxite.
IV. Aluminium can be extracted from china clay.
a) Only I
b) Only II
c) III & IV
d) I, II & III

Find the wrong statement

5 x 2 = 10

22.

a) Metallic oxides can be reduced by an alumino thermic process.
b) Flux + gangue \(\rightarrow\) slag
c) Silica gangue present in the ore is basic in nature
d) Cu₂S + FeS \(\rightarrow\) Copper matter

23.

a) Germanium is used as an semi conductor
b) Stainless steel is an important alloy of Aluminum
c) Zinc sulphide is used in making luminous paints.
d) Brass an alloy of zinc is used in water valves

24.

a) Aluminium is used to produce die-castings
b) Gold nanoparticles used as an catalysts
c) Copper is the first metal used by the human
d) Brass is an alloy of zinc and copper

25.

About "Van-Arkel''
a) Van-Arkel method used for refining Zirconium.
b) Aluminium is a bad conductor of heat.
c) Aluminium shows high resistance to corrosion.
d) Aluminium is a good conductor of heat

26.

About "Electrolytic refining"
a) The crude metal is refined by electrolysis.
b) The rods of impure metal are used as cathode.
c) Thin strips of pure metal are used as cathode.
d) Less electropositive impurities removed as anode mud.

Generic 5

2 x 5 = 10

27.

Write a notes on different types of silicones.

28.

Write note on the structure of diborane.

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Answers Key:

Multiple Choice Question

5 x 1 = 5

(a)
Al

(b)
Al₂O₃

(b)
Al₂O₃.nH₂O

Generic 2

3 x 2 = 6

Diborane adds on to alkenes and alkynes in ether solvent at room temperature. This reaction is called hydroboration.
\({ B }_{ 2 }{ H }_{ 6 }+6RCH=CHR\longrightarrow 2B(RCH_2-{ CH }R)_{ 3 }B\)

Oxides of Carbon	Structure	Parameters
CO		Three electron pairs are shared between carbon and oxygen. The C-O bond distance is 1.128\(\overset{o}{A}\).
CO₂		Equal bond distance for the both C-O bonds. Two C-O sigma bond, It has 3c-4e bond.

The reaction of CO with hydrogen at a pressure of less than 50 atm using metal catalysts at 500 - 700 K yields saturated and unsaturated hydrocarbons.
\(nCO+(2n+1){ H_2 }\longrightarrow C_{ n }{ H }_{ (2n+2) }+{ nH }_{ 2 }O\)
\(nCO+2n{ H }_{ 2 }\longrightarrow { C }_{ n }{ H }_{ 2n }+{ nH }_{ 2 }O\)

Generic 3

3 x 3 = 9

1. CO₂ is used to produce an inert atmosphere for chemical processing
2. Biologically, it is important for photosynthesis.
3. It is also used as fire extinguisher and as a propellant gas.
4. It is used in the production of carbonated beverages and in the production of foam.

10.

1. It melts at 365 K on heating.
2. At 475 K potash alum loses water of hydration and swells up. The swollen mass is known as burnt alum.
\(\mathrm{K}_{2} \mathrm{SO}_{4} \cdot \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3} \cdot 24 \mathrm{H}_{2} \mathrm{O} \stackrel{500 \mathrm{~K}}{\longrightarrow} \mathrm{K}_{2} \mathrm{SO}_{4} \cdot \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}+24 \mathrm{H}_{2} \mathrm{O}\)
Burnt Alum

11.

(i) Silicones are used for low temperature lubrication and in vacuum pumps, high temperature oil baths etc.
(ii) They are used for making water proofing clothes.
(iii) They are used as insulting material in electrical motor and other appliances.
(iv) They are mixed with paints and enamels to make them resistant towards high temperature, sunlight, dampness and chemicals.

Assertion and reason

5 x 2 = 10

12.

c) Assertion is true, but reason is false

13.

d) Both assertion and reason are false

14.

d) Both (A) and (R) are false

15.

b) Both (A) and (R) are true and (R) is not the correct explanation of (A).

16.

a) Both (A) and (R) are true and (R) is the correct explanation of (A)

One or Two Words / Correct Statement

5 x 1 = 5

17.

()
I, II, III & IV

18.

()
I, II & III

19.

()
I, II & IV

20.

()
I, III & IV

21.

()
I, II, III

Find the wrong statement

5 x 2 = 10

22.

Silica gangue present in the ore is basic in nature

23.

Stainless steel is an important alloy of Aluminum

24.

Aluminium is used to produce die-castings

25.

Aluminium is a bad conductor of heat.

26.

The rods of impure metal are used as cathode

Generic 5

2 x 5 = 10

27.

(i) Linear silicones:
They are obtained by the hydrolysis and subsequent condensation of dialkyl or diaryl silicon chlorides.
(a) Silicone rubbers:
These silicones are bridged together by methylene or similar groups.
(b) Silicone resins:
They are obtained by blending silicones with organic resins such as acrylic esters.
(ii) Cyclic silicones:
These are obtained by the hydrolysis of R₂SiCl₂.
(iii) Cross linked silicones:
They are obtained by hydrolysis of RSiCl₃.

28.

(i) In diborane two BH₂ units are linked by two bridged hydrogens.
(ii) It has eight B-H bonds.
(iii) Diborane has only 12 valance electrons.
(iv) The four terminal B-H- bonds is 2c - 2e bond (two centre - two electron bond.)
(v) Two three centred B - H - B bonds two electrons each. (3c - 2e).
(vi) In diborane, the boron is sp³ hybridised
(vii) Three of the four sp³ hydridised orbitals contains single electron and the fourth orbital is empty.