Chemistry Test

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Chemistry Test - 19

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Weekly Quiz Competition

Question 1
1 / -0

Which one of the following is incorrect?

A
An element which has high electronegativity always has high electron gain enthalpy.

B
Electron gain enthalpy is the property of an isolated atom.

C
Electronegativity is the property of a bonded atom.

D
Both electronegativity and electron gain enthalpy are usually directly related to nuclear charge and inversely related to atomic size.

Solution

Elements with high electronegativity usually have high electron gain enthalpies, but this does not happen all the time.

If you take the example of nitrogen, it's electronegativity is one of the highest.

But if you look at its electron gain enthalpy, you actually need to supply energy to add the electron because nitrogen has a half-filled configuration which is stable.
Question 2
1 / -0

Which one of these are point sources of pollution?

A
The runoff of fertilizers from farm animals and crop land

B
Air pollutants getting washed or deposited to earth

C
Oil wells

D
Storm water drainage from lawns, parking lots, and streets

Solution

Oil wells are the point sources of water pollution whereas others are non-point sources of pollution. Point sources are single, identifiable source of pollution.
Question 3
1 / -0

Express 6' 10” in SI units.

A
2.06 m

B
2.07 m

C
2.09 m

D
2.08 m

Solution

1 Feet $=12$ inches
$\therefore 6^{\prime} 10^{\prime}=(12 \times 6)+10=82$ inches
1 inch $=2.54 \mathrm{cm}$
$\therefore 82$ inches $=(82 \times 2.54) \mathrm{cm}$
$\begin{array}{ll} \text { (centi }\left.=10^{-2}\right) & =208.28 \mathrm{cm}=208.28 \times 10^{-2} \mathrm{m} \\ =2.0828 \mathrm{m}\end{array}$
Question 4
1 / -0

The pair of gases responsible for acid rain are:

A
H₂, O₃

B
CH₄, O₃

C
NO₂, SO₂

D
CO, CH₄

Solution

Processes involved in acid deposition (note that only $S O_{2}$ and $N O_{x}$ play a significant role in acid rain). Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals and infrastructure. Acid rain is caused by emissions of sulphur dioxide and nitrogen oxide.
Question 5
1 / -0

The rate of diffusion of Methane at certain temperature is 2 times that of gas X. The molecular mass of X is___.

A
64

B
32

C
4

D
8

Solution

\[
\sqrt{\frac{M_{x}}{16}}=\sqrt{\frac{r_{C H_{4}}}{r_{x}}}=\sqrt{\frac{2}{1}}
\]
Squaring both sides, we get
\[
M_{x}=16 \times 4=64
\]
Question 6
1 / -0

Which of the following element is most electropositive?

A
H

B
Mg

C
Ca

D
Si

Solution

Alkali or alkaline earth metals present on left side are highly electropositive. Ca and Mg both belong to same alkaline earth metal group. This electropositive character increases down the group with the increase in atomic size so Ca is more electropositive.
Question 7
1 / -0

The correct statement is:

A
one mole each of benzene and hydrogen when reacted gives 1/3 mole of cyclohexane and 2/3 mole unreacted hydrogen

B
it is easier to hydrogenate benzene when compared to cyclohexene

C
cyclohexadiene and cyclohexene cannot be isolated with ease during controlled hydrogenation of benzene

D
hydrogenation of benzene to cyclohexane is an endothermic process

Solution

During hydrogenation of benzene it is very difficult to obtain cyclohexene and cyclohexadiene.
Question 8
1 / -0

The hydrogen bond is shortest in

A
N - H .......O

B
F - H ...........O

C
N - H.........F

D
F - H ........F

Solution

F is most electronegative atom
Question 9
1 / -0

$C H_{3} C \equiv C H \stackrel{N a N H_{2}}{\longrightarrow} X \frac{C H_{2} C H_{2} B r}{\longrightarrow} Y .$ Identify the product 'Y' is

A
Pent - 2 - ene

B
Pent - 2 - yne

C
Pent - 1 - yne

D
Pentane

Solution

X is $C H_{3} - C \equiv C^{-} N a^{+}$

Y is $C H_{3} - C \equiv C - C H_{2} - C H_{3}$

The first step removes the terminal hydrogen from the given substrate (reactant on the left). Such a removable hydrogen is called an acidic hydrogen. In the next step, the nucleophile - which is rich in electrons - attacks the $C - B r$ bond of ethyl bromide. Because of the difference in electronegativity between carbon andbromine, this $C - B r$ bond is polar - meaning, the bonding electrons are closer to the more electronegative bromine. This gives rise to the possibility of the carbon of the $C - B r$ bond having a slight deficit of electrons; let's just say that this carbon misses electrons and that is where the electron-rich terminal carbon of $C H_{3} - C \equiv C^{-}$ comes in. Hence, the reaction.
Question 10
1 / -0

In the manufacture of ammonia by Haber's process, N2(g) + 3H2(g) ⇋ 2NH3(g) + 92.3kJ. Which of the following conditions is unfavourable?

A
Reducing the temperature

B
Removing ammonia as it is formed

C
Increasing the temperature

D
Increasing the pressure

Solution

As the reaction is exothermic, increasing temperature, equilibrium will shift towards left.

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Chemistry Test - 19

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Chemistry Test - 19

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Question 1

An element which has high electronegativity always has high electron gain enthalpy.

Electron gain enthalpy is the property of an isolated atom.

Electronegativity is the property of a bonded atom.

Both electronegativity and electron gain enthalpy are usually directly related to nuclear charge and inversely related to atomic size.

Solution

Question 2

The runoff of fertilizers from farm animals and crop land

Air pollutants getting washed or deposited to earth

Oil wells

Storm water drainage from lawns, parking lots, and streets

Solution

Question 3

2.06 m

2.07 m

2.09 m

2.08 m

Solution

Question 4

H2, O3

CH4, O3

NO2, SO2

CO, CH4

Solution

Question 5

64

32

4

8

Solution

Question 6

H

Mg

Ca

Si

Solution

Question 7

one mole each of benzene and hydrogen when reacted gives 1/3 mole of cyclohexane and 2/3 mole unreacted hydrogen

it is easier to hydrogenate benzene when compared to cyclohexene

cyclohexadiene and cyclohexene cannot be isolated with ease during controlled hydrogenation of benzene

hydrogenation of benzene to cyclohexane is an endothermic process

Solution

Question 8

N - H .......O

F - H ...........O

N - H.........F

F - H ........F

Solution

Question 9

Pent - 2 - ene

Pent - 2 - yne

Pent - 1 - yne

Pentane

Solution

Question 10

Reducing the temperature

Removing ammonia as it is formed

Increasing the temperature

Increasing the pressure

Solution

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H₂, O₃

CH₄, O₃

NO₂, SO₂

CO, CH₄