Chemistry Test

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Chemistry Test - 9

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Weekly Quiz Competition

Question 1
4 / -1

The group \(14\) elements form _____________ hydrides.

A
metallic

B
ionic

C
covalent

D
None of these

Solution

The group \(14\) elements form covalent hydrides.

All the members of group \(14\) form covalent hydrides, their number and ease of formation decreases down the group along with their thermal stability while their reducing character increases down the group.
Question 2
4 / -1

H₂O₂ changes Cr₂O₇^2- ion to CrO₅ in an acidic medium, the oxidation state of Cr in CrO₅ is

A
+6

B
+5

C
+10

D
+3

Solution

When H₂O₂ is added to an acidified solution of a dichromate, Cr₂O₇^2-, aO deep blue coloured complex, chromic peroxide, CrO₅ or CrO(O₂)₂ is formed.

Cr₂O₇^2-+2H⁺+4H₂O--->2CrO(O₂)₂+5H₂O

This deep blue coloured complex.

The oxidation state of Cr is +6 due to the presence of two peroxide linkages which can be calculated as Cr peroxide normal

X+(-1)4+(-2)= 0

X-6= 0

X= +6
Question 3
4 / -1

The expression to be used to calculate the \(\mathrm{pH}\) of sodium bicarbonate solution (where \(K_{a_{1}}^{o}\) and \(K_{a_{2}}^{o}\) stand for the standard ionisation of \(H C O_{3}^{-}\) and \(C O_{3}^{2-}\), respectively) is

A

\(\mathrm{pH}=\mathrm{pK}_{\mathrm{a} 1}^{0} / \mathrm{pK}_{\mathrm{a} 2}^{\circ}\)

B

\(\mathrm{pH}=\mathrm{pK}_{\mathrm{ar}}^{0}+\mathrm{pK}_{\mathrm{a} 2}^{0} 22\)

C

\(\mathrm{pH}=\frac{1}{2}\left(\mathrm{pK}_{\mathrm{at}}^{\mathrm{o}}+\mathrm{pK}_{\mathrm{a} 2}^{\mathrm{O}}\right)\)

D

\(\mathrm{pH}=\frac{1}{2}\left(\mathrm{pK}_{\mathrm{a} 1}^{0}-\mathrm{pK}_{\mathrm{a} 2}^{0}\right)\)

Solution

\(\mathrm{NaHCO}_{3}\) is amphiprotic species just like \(\mathrm{NaHSO}_{4}, \mathrm{NaHS}, \mathrm{Na}_{2} \mathrm{HPO}_{4}, \mathrm{NaH}_{2} \mathrm{PO}_{4}\) etc.

In such cases the solution \(\mathrm{pH}\) is dependent on the two ionization constants of the amphiprotic substance and independent of the concentration of the amphiprotic substance in the solution. However, they do not hold pH well and are not effective as buffer solutions. Here the trick is to use the formula,

\(\mathrm{pH}=\frac{1}{2}\left(\mathrm{pK}_{\mathrm{at}}^{0}+\mathrm{pK}_{\mathrm{a} 2}^{0}\right)\) where \(\mathrm{K}_{\mathrm{a} 1} \& \mathrm{~K}_{\mathrm{a} 2}\) are dissociation constants of the conjugate acid of amphiprotic species.

For \(\mathrm{NaHCO}_{3}, \mathrm{pH}\) is \(\frac{(6.37+10.25)} {2}=8.31\)
Question 4
4 / -1

What are elements F, Cl, Br, I and At commonly known as?

A
Actinoids

B
Transition elements

C
Halogens

D
Rare earth elements

Solution

The elements Fluorine (Fl, 9) , Chlorine (Cl, 17), Bromine (Br, 35), Iodine (I, 85), Astatine (At, 85), Ununseptium (Uus) / Tennessee (Ts, 117) are called Halogens.

Halogens are 17th group elements and have ns2 np5 outermost configuration and belong to the P-Block Elements.

Hence, the correct option is (C)
Question 5
4 / -1

The phenomenon in which polar crystals on heating produce electricity is called:

A
Pyro-electricity

B
Piezo-electricity

C
Ferro-electricity

D
Ferri-electricity

Solution

Some of the polar crystals when heated produce an electric current. This phenomenon is called Pyro-electricity or pyroelectric effect.
Question 6
4 / -1

Which of the following compounds is not a food additive?

A
Tartrazine

B
Norethisterone

C
Benzoate of soda

D
Acesulfame potassium

Solution

Norethisterone, also known as norethindrone and sold under many brand names, is a progestin medication used in birth control pills, menopausal hormone therapy, and for the treatment of gynecological disorders.
Question 7
4 / -1

Given that \(E°\) values of \(Ag^{+}|Ag, K^{+}|K, Mg^{2+}|Mg\) and \(Cr^{3+}|Cr\) are \(0.80 V, – 2.93 V, – 2.37 V\) and \(– 0.74 V\), respectively, which of the following orders regarding the reducing power of metals is correct?

A
\(Ag > Cr > Mg > K\)

B

\(Ag< Cr< Mg< K\)

C

\(Ag >Cr >K >Mg\)

D

\(Cr >Ag >Mg >K\)

Solution

\(K^{+}+e^{\prime} \Rightarrow K\)
\(E^{O}=-2.93 V\)
\(Ag++e-\Rightarrow Ag\)
\(E^{O}=0.80 V\)
\(Mg^{+2}+e^{-} \Rightarrow Mg\)
\(E^{0}=-2.37 V\)
\(Cr^{+3}+e^{-} \Rightarrow Cr\)
Reducing the power means self oxidation \((SoP)\).
So, increasing order of reducing power is
\(Ag < Cr < Mg < K\)
Question 8
4 / -1

In the given reaction

\(A\) and \(B\) will respectively be:

A

\(\mathrm{H}_{3} \mathrm{C}-\mathrm{CH}_{2}-\mathrm{CHO}\) and \({CH}_{3}-\mathrm{CH}_{2}-\mathrm{CHO}\)

B

\(\mathrm{H}_{3} \mathrm{C}-\mathrm{CHO}\) and \({CH}_{3}-\mathrm{CH}_{2}-\mathrm{CHO}\)

C

\(\mathrm{H}_{3} \mathrm{C}-\mathrm{CHO}\) and \(CH_{3}-\mathrm{CHO}\)

D

Solution

Compound is \(\beta\) -hydroxy aldehyde hence the reaction is aldol addition. \(A\) and \(B\) can be known by retro aldol addition as follows:
Question 9
4 / -1

Choose the correct answer. A thermodynamic state function is a quantity:

A
used to determine heat changes

B
whose value is independent of path

C
used to determine pressure volume work

D
whose value depends on temperature only

Solution

A thermodynamic state function is a quantity whose value is independent ofthe path.Its value depends on initial and final states and is independent of the path followed. Functions like \(p, V, T\), etc. depend only on the state of a system and not onthe path.A state function describes the equilibrium state of a system.
Question 10
4 / -1

Elements of group \(13\) are part of which of the following block of elements?

A
p- block

B
s-block

C
b-block

D
d-block

Solution

Elements of group 13 are part of p-block elements.

The last electron enters in the outermost p-orbital in the p block elements, from group 13 to group 18 the entire elements belong to p-block, whereas group 13 is called a boron family. It includes the elements boron, aluminum, gallium, indium and thallium.

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Chemistry Test - 9

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Chemistry Test - 9

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Question 1

metallic

ionic

covalent

None of these

Solution

Question 2

+6

+5

+10

+3

Solution

Question 3

\(\mathrm{pH}=\mathrm{pK}_{\mathrm{a} 1}^{0} / \mathrm{pK}_{\mathrm{a} 2}^{\circ}\)

\(\mathrm{pH}=\mathrm{pK}_{\mathrm{ar}}^{0}+\mathrm{pK}_{\mathrm{a} 2}^{0} 22\)

\(\mathrm{pH}=\frac{1}{2}\left(\mathrm{pK}_{\mathrm{at}}^{\mathrm{o}}+\mathrm{pK}_{\mathrm{a} 2}^{\mathrm{O}}\right)\)

\(\mathrm{pH}=\frac{1}{2}\left(\mathrm{pK}_{\mathrm{a} 1}^{0}-\mathrm{pK}_{\mathrm{a} 2}^{0}\right)\)

Solution

Question 4

Actinoids

Transition elements

Halogens

Rare earth elements

Solution

Question 5

Pyro-electricity

Piezo-electricity

Ferro-electricity

Ferri-electricity

Solution

Question 6

Tartrazine

Norethisterone

Benzoate of soda

Acesulfame potassium

Solution

Question 7

\(Ag > Cr > Mg > K\)

\(Ag< Cr< Mg< K\)

\(Ag >Cr >K >Mg\)

\(Cr >Ag >Mg >K\)

Solution

Question 8

\(\mathrm{H}_{3} \mathrm{C}-\mathrm{CH}_{2}-\mathrm{CHO}\) and \({CH}_{3}-\mathrm{CH}_{2}-\mathrm{CHO}\)

\(\mathrm{H}_{3} \mathrm{C}-\mathrm{CHO}\) and \({CH}_{3}-\mathrm{CH}_{2}-\mathrm{CHO}\)

\(\mathrm{H}_{3} \mathrm{C}-\mathrm{CHO}\) and \(CH_{3}-\mathrm{CHO}\)

Solution

Question 9

used to determine heat changes

whose value is independent of path

used to determine pressure volume work

whose value depends on temperature only

Solution

Question 10

p- block

s-block

b-block

d-block

Solution

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