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Chemistry 1 Marks Question

The d- and f-Block Elements · Gujarat Board (GSEB) STD 12 Science (GSEB - English Medium). 34 questions.

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MCQ 11 Mark
Give reasons why $Zn , Cd , Hg$ and Cn are not transition elements.
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Answer
The reason why $Zn , Cd , Hg$ and Cn are not considered transition elements is because of their fully filled d-orbitals.
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Question 21 Mark
'Spin only' magnetic for $Cu _{(\rho q )}^{+2}$ ion. Calculate the magnetic moment.
Answer
$\mu=\sqrt{n(n+2)}$ B.M. $=\sqrt{1(1+2)}=\sqrt{3}$ B.M. $=1.7 B . M$.
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Question 51 Mark
Actinoid contraction is more than lanthanoid contraction, why?
Answer
Due to weak shielding effect of 5 f electrons, actinoid contraction is more than lanthanoid contraction.
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Question 61 Mark
Instruments used in surgery are cleaned by $KMnO _4$, why?
Answer
Due to the germicidal properties of $KMnO _4$, it can be treated surgically. That is why it is used to clean the equipment.
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Question 81 Mark
What are parauranium elements?
Answer
Radioactive and artificial elements U are called parauranium elements.
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Question 91 Mark
Write the maximum oxidation state displayed by actinoids.
Answer
Actinoids exhibit maximum oxidation state of $+7$.
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Question 101 Mark
$La ( OH )_3$ is more basic than $Lu ( OH )_3$, why?
Answer
From La to Lu , the alkaline nature of hydroxide decreases because their ionic radius decreases, hence $La ( OH )_3$ is more basic than $Lu ( OH )_3$.
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Question 111 Mark
What is called lanthanoid contraction?
Answer
As the atomic number increases from La to Lu , there is a decrease in the atomic and ionic radii, this is called lanthanoid contraction.
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Question 131 Mark
Write equations showing the products formed when dichromate ion is reacted with hyrogen peroxide.
Answer
$Cr _2 O _7^{2-}+4 H _2 O _2+2 \stackrel{+}{ H } \rightarrow 2 CrO _5+5 H _2 O$
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Question 141 Mark
Explain the use of Bayer reagent.
Answer
Unsaturated is tested with Bayer's reagent (1\% alkaline $KMnO _4$ ).
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Question 151 Mark
Write the products formed when KI solution is treated with acidic and basic $KMnO _4$.
Answer
When KI solution is reacted with acidic $KMnO _4$, iodine $\left( I _2\right)$ is obtained and when it is reacted with alkaline $KMnO _4$, potassium iodate $\left( KIO _3\right)$ is obtained.
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Question 161 Mark
Orange solution of $K _2 Cr _2 O _7$ contains strong alkali $( NaOH$ or KOH $)$ the solution turns yellow. Why?
Answer
On adding strong alkali to the orange solution of $K _2 Cr _2 O _7$, chromate is formed, hence the solution turns yellow.
$
\underset{\text { orange }}{Cr_2 O_7^{2-}}+2 \overline{O} H \rightarrow \underset{\text { yellow }}{2 CrO_4^{2-}}+H_2 O
$
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Question 181 Mark
Write the equation of disproportionation of $Mn ^{ VI }$
Answer
$3 \stackrel{ VI }{ MnO _4^{2-}}+4 H ^{+} \rightarrow 2 \stackrel{ VII }{ Mn O _4^{-}}+\stackrel{ VV }{ MnO _2}+2 H _2 O$
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Question 191 Mark
$Zn ^{2+}$ is diamagnetic while $Cu ^{2+}$ is paramagnetic, why?
Answer
$Zn ^{+2}\left(3 d^{10}\right)$ does not have a single unpaired electron whereas $Cu ^{2+}\left(3 d^9\right)$ has one unpaired electron present, hence $Zn ^{2+}$ is diamagnetic but $Cu ^{2+}$ is paramagnetic.
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Question 221 Mark
Transition metals form alloys, why?
Answer
Due to similarly in radii of post-transition elements and their characteristic properties, these alloys are easily made.
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Question 251 Mark
Which has the lowest melting point among transition elements?
Answer
Mercury ( Hg ) has the lowest melting point among post-transition elements.
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Question 261 Mark
$Cu , Ag$ and Au have $d ^{10}$ configurations, yet they are transition elements. Why?
Answer
$Cu , Ag$ and Au cations do not have $d ^{10}$ configuration, hence they are transition elements.
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Question 271 Mark
Arrange $CrO , Cr _2 O _3, CrO _2$ and $CrO _3$ in increasing order of acidic properties.
Answer
$CrO < Cr _2 O _3< CrO _2< CrO _3$
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Question 281 Mark
Which are the volatile metals in a $d$-block and why?
Answer
$Zn , Cd$ and Hg volatile metals in d-block because their melting and boiling points are low.
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Question 301 Mark
Which of the following oxides will have maximum covalent property? $SC _2 O _3, TiO _2, Mn _2 O _7$ and $V _2 O _5$.
Answer
$Mn _2 O _7$
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Question 311 Mark
What is the general oxidation state of 3d series of transition elements?
Answer
The general oxidation state of the 3d series of post-transition elements is +2 .
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Question 331 Mark
Name those elements of the first transition series which show only one type of oxidation state.
Answer
Sc and Zn .
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Question 341 Mark
Write the electronic configuration of $Ni ^{2+}$.
Answer
$Ni ^{2+}=1 s^2 2 s^2 2 p ^6 3 s^2 3 p ^6 3 d^8 4 s^0$
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