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Chemistry 1 Marks Question

PART - 2 CH - 7 Redox Reactions · Gujarat Board (GSEB) STD 11 Science (GSEB - English Medium). 20 questions.

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Question 31 Mark
Give the direction of flow of current in following electrochemical cell :
$Zn\left|Zn^{2+} \| Ag^{+}\right| Ag$
Answer
The flow of electric current is from Ag electrode to zinc electrode because flow of electron is from zinc electrode to silver electrode.
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Question 41 Mark
Write an example of disproportionation reaction.
Answer
$Cl +2 \overline{ O } H \longrightarrow \overline{ C }+ Cl \bar{O}+ H _2 O$
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Question 51 Mark
Arrange $I ^{-}, Br ^{-}, Cl ^{-}$and $F ^{-}$in reducing strength.
Answer
$I ^{-}> Br ^{-}> Cl ^{-}> F ^{-}$
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Question 61 Mark
Balance the following reaction :
$IO _3^{-}+ H ^{+} \longrightarrow I ^{-}+ H _2 O$
Answer
$IO _3^{-}+6 H ^{+}+6 e ^{-} \longrightarrow I ^{-}+3 H _2 O$
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Question 71 Mark
Write the main types of Redox reactions.
Answer
The Redox reactions are of four types :
(a) combination
(b) decomposition
(c) displacement
(d) disproportionation reaction.
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Question 91 Mark
Give the balanced equation of following :
$I _2+ OH ^{-} \longrightarrow I ^{-}+ IO _3^{-}+ H _2 O$
Answer
$3 I _2+6 OH ^{-} \longrightarrow 5 I ^{-}+ IO _3^{-}+3 H _2 O$
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Question 101 Mark
What is the oxidation number of S in dimethyl sulphoxide?
Answer
$\left( CH _3\right)_2 S=0 \Rightarrow+1(2)+x-2=0 \Rightarrow x=0$
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Question 111 Mark
Calculate the oxidation number of Al in $LiAlH _4$.
Answer
 $LiAlH _4$ : It is a hydride. Hence, the oxidation number of Hydrogen is -1 .
$\begin{aligned} LiAlH _4\\ +1+x-1(4) =0 \\ x=+3\end{aligned}$
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Question 131 Mark
Why the blue colour of $CuSO _4$ solution slowly get disappeared, when Zn rod is placed in it?
Answer
In this reaction $Cu ^{+2}$ ion get converted to Cu . Hence the blue colour of solution gets disappeared.
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Question 141 Mark
Why the $AgNO _3$ solution become blue when Cu rod is dipped in it?
Answer
Because of the formation of $Cu ^{+2}$ ion, the colour of solution becomes blue and Ag gets free.
$Cu ( s )+2 AgNO _3( aq ) \longrightarrow Cu \left( NO _3\right)( aq )+2 Ag ( s )$
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Question 151 Mark
In $H _2 S_2 O _8$, what will be the oxidation number of S atom?
Answer
$+6$ (In this, two oxygen atom form peroxide).
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Question 161 Mark
What is the oxidation number of nitrogen atom in $N _3 H$ ?
Answer
$-1 / 3$
$\begin{array}{l} N _3 H \\ 3 x+1=0 \\ x=\frac{-1}{3}\end{array}$
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Question 171 Mark
Calculate the oxidation number of Fe in $Na _2\left[ Fe ( CN )_5 NO \right]$
Answer
$+3$
$\begin{array}{l} Na _2\left[ Fe ( CN )_5 NO \right] \\ +1(2)+x+5(-1)+0=0 \\ x=+3\end{array}$
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Question 181 Mark
Calculate the oxidation number of Fe is $K _3\left[ Fe ( CN )_6\right]$.
Answer
 $+3$
$\begin{aligned} K _3 Fe ( CN )_6  \\ +3+x+6(-1) & =0 \\ x  =+3\end{aligned}$
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Question 191 Mark
Find out the valency and oxidation number of $S \text { in } S_8 .$
Answer
In $S_8$ the valency of $S$ is 2 while oxidation number in zero.
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Question 201 Mark
What is the oxidation state of S in $S _2 O _3{ }^{2-}$ ?
Answer
  $\begin{array}{l}+2 \\ S_2 O _3{ }^{2-} \\ 2 x+3(-2)=-2 \\ 2 x=-2+6 \\ x=+2\end{array}$
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