Chemistry Test 208

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Chemistry Test 208

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Weekly Quiz Competition

Question 1
4 / -1

What is the value of electron gain enthalpy of Na⁺ if IE₁ of Na = 5.1eV ?

A
- 5.1 eV

B
-10.2 eV

C
+2.55 eV

D
+10.2 eV

Solution

Na → Na⁺+ e⁻;ΔH = 5.1eV

Na⁺+ e⁻→ Na; ΔH = −5.1eV
Question 2
4 / -1

Among the elements Ca, Mg, P and Cl, the order of increasing atomic radii is

A
Mg < Ca < Cl < P

B
Cl < P < Mg < Ca

C
P < Cl < Ca < Mg

D
Ca < Mg < P < Cl

Solution

The atomic radii decrease on moving from left to right in a period, thus order of sizes for Cl, P and Mg is Cl < P < Mg. Down the group size increases.

Thus overall order is : Cl < P < Mg < Ca
Question 3
4 / -1

Which one of the following arrangements represents the correct order of electron gain enthalpy (with negative sign) of the given atomic species

A
S < O < Cl < F

B
Cl < F < S < O

C
F < Cl < O < S

D
O < S < F < CI

Solution

Cl-atom has the highest electron affinity in the periodic table. F being a member of group 17 has higher electron gain enthalpy than S which belongs to group 16 . This in turn is higher than the electron affinity of O -atom. Thus, Cl > F > S > O

It is worth noting that the electron gain enthalpy of oxygen and fluorine, the members of the second period, have less negative values than the elements sulphur and chlorine of the third period.

This is due to small size of the atoms of oxygen and fluorine. As a result, there is a strong interelectronic repulsion when extra electron is added to these atoms, i.e., electron density is high and the addition of an extra electron is not easy.
Question 4
4 / -1

With which of the following electronic configuration an atom has the lowest ionisation enthalpy?

A
1s²2s²2p³

B
1s²2s²2p⁵3s¹

C
1s²2s²2p⁶

D
1s²2s²2p⁵

Solution

The larger the atomic size, smaller is the value of the ionisation enthalpy. Again higher the screening effect, lesser is the value of ionisation potential. Hence option (b) has lowest ionisation enthalpy.
Question 5
4 / -1

The ions O²⁻,F⁻,Na⁺, Mg²⁺ and Al³⁺ are isoelectronic. Their ionic radii show

A
a significant increase from O²⁻ to Al³⁺

B
a significant decrease from O²⁻ to Al³⁺

C
an increase from O²⁻ to F⁻ and then decrease from Na⁺ to Al³⁺

D
a decrease from O²⁻ to F⁻ and then increase from Na⁺ to Al³⁺

Solution

Amongst isoelectronic ions, ionic radii of anions is more than that of cations. Further size of the anion increases with increase in -ve charge and size of cation decreases with increase in +ve charge. Hence, correct order is

O²⁻ > F⁻ > Na⁺ > Mg²⁺ > Al³⁺
Question 6
4 / -1

Which of the following are not state functions?

(I) q + w

(II) q

(III) w

(IV) H - Ts

A
(I) (II) and (III)

B
(II) and (III)

C
(I) and (Iv)

D
(II) (III) and (Iv)

Solution

State functions or state variables are those which depend only on the state of the system and not on how the state was reached.

Path function depends on the path followed during a process as well as the end states. Work and heat are the path functions.
Question 7
4 / -1

The enthalpy and entropy change for the reaction:

Br_2(l) + Cl_2(g) → 2BrCl_(g)

are 30 kJmol⁻¹ and 105 JK⁻¹mol⁻¹ respectively. The temperature at which the reaction will be in equilibrium is

A
300K

B
285.7 K

C
273 K

D
450 K

Solution
Question 8
4 / -1

Stainless steel does not rust because

A
Chromium and nickel combine with iron

B
Chromium forms an oxide layer and protects iron from rusting

C
Nickel present in it, does not rust

D
Iron forms Ahard chemical compound with chromium present in it

Solution

Chromium is more electropositive metal than iron. In stainless steel, chromium forms an oxide layer and thus it protects steel from corrosion.
Question 9
4 / -1

In electrolytic purification, which of the following is made of impure metal?

A
Anode

B
Cathode

C
Both (a) and (b)

D
None of these

Solution

In the process of electro decomposition for purification of metal, impure metal acts as anode.
Question 10
4 / -1

The resistance of 1N solution of acetic acid is 250 ohm, when measured in a cell having a cell constant of 1.15 cm⁻¹. The equivalent conduction (in ohm⁻¹cm². equiv⁻¹) of 1N acetic acid is ......

A
18.4

B
9.2

C
4.6

D
2.3

Solution

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Chemistry Test 208

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Question 1

- 5.1 eV

-10.2 eV

+2.55 eV

+10.2 eV

Solution

Question 2

Mg < Ca < Cl < P

Cl < P < Mg < Ca

P < Cl < Ca < Mg

Ca < Mg < P < Cl

Solution

Question 3

S < O < Cl < F

Cl < F < S < O

F < Cl < O < S

O < S < F < CI

Solution

Question 4

1s22s22p3

1s22s22p53s1

1s22s22p6

1s22s22p5

Solution

Question 5

a significant increase from O2− to Al3+

a significant decrease from O2− to Al3+

an increase from O2− to F− and then decrease from Na+ to Al3+

a decrease from O2− to F− and then increase from Na+ to Al3+

Solution

Question 6

(I) (II) and (III)

(II) and (III)

(I) and (Iv)

(II) (III) and (Iv)

Solution

Question 7

300K

285.7 K

273 K

450 K

Solution

Question 8

Chromium and nickel combine with iron

Chromium forms an oxide layer and protects iron from rusting

Nickel present in it, does not rust

Iron forms Ahard chemical compound with chromium present in it

Solution

Question 9

Anode

Cathode

Both (a) and (b)

None of these

Solution

Question 10

18.4

9.2

4.6

2.3

Solution

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1s²2s²2p³

1s²2s²2p⁵3s¹

1s²2s²2p⁶

1s²2s²2p⁵

a significant increase from O²⁻ to Al³⁺

a significant decrease from O²⁻ to Al³⁺

an increase from O²⁻ to F⁻ and then decrease from Na⁺ to Al³⁺

a decrease from O²⁻ to F⁻ and then increase from Na⁺ to Al³⁺