CBSE 11th Standard Chemistry Subject HOT Questions 5 Mark Questions With Solution 2021
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CBSE 11th Standard Chemistry Subject HOT Questions 5 Mark Questions With Solution 2021
11th Standard CBSE
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Reg.No. :
Chemistry
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If uncertainties in the measurement of position and momentum of an electron are found to be equal in magnitude, what is the uncertainty in the measurement of velocity of the electron? Comment on the result obtained?
(a) -
Iron pieces are attracted towards a magnet but zinc pieces are not. Why?
(a) -
On a ship sailing in Pacific ocean where temperature is \(23.4^{ \circ }C\) , a balloon is filled with 2L air. What will be the volume of the balloon when the ship reaches Indian ocean, where temperature is \(26.1^{ \circ }C\) ?
(a) -
Calculate the pH of 10-8M HCl
(a) -
An ionic hydride of an alkali metal has significant covalent character and is almost unreactive towards oxygen and chlorine. This is used in the synthesis of other useful hydrides. Write its reaction with \({ Al }_{ 2 }{ Cl }_{ 6 }\)
(a) -
When the first element of the periodic table is treated with dioxygen, it gives a compound whose solid state floats on its liquid state. This compound has an ability to act as an acid as well as a base. What products will be formed when this compound undergoes auto ionisation?
(a)
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CBSE 11th Standard Chemistry Subject HOT Questions 5 Mark Questions With Solution 2021 Answer Keys
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\(\triangle x\times \triangle P=\frac { h }{ 4\pi } ,\ As \ \triangle x=\triangle P\)
\( \therefore { \left( \triangle P \right) }^{ 2 }=\frac { h }{ 4\pi } or\quad \triangle P=\sqrt { \frac { h }{ 4\pi } } or \ m\times \triangle v=\sqrt { \frac { h }{ 4\pi } } \)
\( or \ \triangle v=\frac { 1 }{ m } \sqrt { \frac { h }{ 4\pi } } =\frac { 1 }{ 9.11\times { 10 }^{ -31 } } \times \sqrt { \frac { 6.626\times { 10 }^{ -34 } }{ 4\times 3.14 } }\)
\( =\frac { 0.726\times { 10 }^{ -17 } }{ 9.11\times { 10 }^{ -31 } } =7.89\times { 10 }^{ 12 }{ ms }^{ -1 }\)
Thus, uncertainty in velocity is greater than the velocity of light which is impossible. Thus, the two uncertainties cannot be equal in magnitude. -
Electronic configuration of iron suggests that it contains unpaired electrons (\(_{ 26 }Fe=\left[ Ar \right] 3d^{ 6 }{ 4s }^{ 2 }\)
and hence it is paramagnetic whereas zinc has no unpaired electron
\((_{ 30 }Zn=\left[ Ar \right] ^{ 18 }3d^{ 10 }{ 4s }^{ 2 }) \) and hence, it is diamagnetic. It is rather repelled by the magnet. -
\(Given,\ { V }_{ 1 }=2L;{ V }_{ 2 }=?\)
\({ T }_{ 2 }=(26.1+273)K=299.1K\)
\( { T }_{ 1 }=(23.4+273)K=296.4K\)
\(According \ to \ Charles \ law,\)
\( \frac { { V }_{ 1 } }{ { T }_{ 1 } } =\frac { { V }_{ 2 } }{ { T }_{ 2 } } or{ V }_{ 2 }=\frac { { V }_{ 1 }{ T }_{ 2 } }{ T_{ 1 } } \)
\(on \ substituting \ the \ corresponding \ values,\ we \ get\)
\(\Rightarrow \ { V }_{ 2 }=\frac { 2L\times 299.1K }{ 296.4K } =2.018L\) -
\(\because \) pH = -log[H+] =-log 10-8 = 8
But this is not true because an acidic solution cannot have pH greater than 7. In this condition,[H+] of water cannot be neglected.
Therefore,[H+]total = [H+]HCl+[H+]\({ H }_{ 2 }O\)= 10-8+10-7
= 10-8(1 + 10) = 11\(\times \)10-8
Now from, pH = -log[H+] = -log(11\(\times \)10-8)
= -log 11-log 10-8 = 6.958 -
It is LiH because it has significant covalent character due to the smallest alkali metal Li. LiH is very stable. It is almost unreactive towards oxygen and chlorine.
It reacts with \({ Al }_{ 2 }{ Cl }_{ 6 }\) to form lithium aluminium hydride.
\(8LiH+{ Al }_{ 2 }{ Cl }_{ 6 }\longrightarrow 2LiAl{ H }_{ 4 }+6LiCl\) -
The first element of the periodic table is H and its molecular form is dihydrogen (H 2). When dihydrogen reacts with dioxygen, water is formed.
Water is a liquid at room temperature. When liquid water freezes, it expands to form ice. In other words, the density of ice is lower than that of liquid water and hence, ice floats over water.
Water is amphoteric in nature, i.e. it acts as an acid in presence of strong bases and as a base in the presence of strong acids.
\(\begin{matrix} { H }_{ 2 }O\left( l \right) \\ { Acid }_{ 1 } \end{matrix}+\begin{matrix} { NH }_{ 3 }\left( aq \right) \\ Base_{ 2 } \end{matrix}\longrightarrow \begin{matrix} { NH }_{ 4 }^{ + }\left( aq \right) \\ { Acid }_{ 2 } \end{matrix}+\begin{matrix} { OH }^{ - }\left( aq \right) \\ Base_{ 1 } \end{matrix}\\ \begin{matrix} { H }_{ 2 }O\left( l \right) \\ Base_{ 1 } \end{matrix}+\begin{matrix} { H }_{ 2 }S\left( aq \right) \\ { Acid }_{ 2 } \end{matrix}\longrightarrow \begin{matrix} { H }_{ 3 }{ O }^{ + }\left( aq \right) \\ { Acid }_{ 1 } \end{matrix}+\begin{matrix} { HS }^{ - }\left( aq \right) \\ Base_{ 2 } \end{matrix}\)
Due to amphoteric character, water undergoes self-ionisation as shown below.
\(\begin{matrix} { H }_{ 2 }O\left( l \right) \\ { Acid }_{ 1 } \end{matrix}+\begin{matrix} { H }_{ 2 }O\left( base \right) \\ Base_{ 2 } \end{matrix}\rightleftharpoons \begin{matrix} { H }_{ 3 }{ O }^{ + }\left( aq \right) \\ { Acid }_{ 1 } \\ \left( Conjugate \ acid \right) \end{matrix}+\begin{matrix} { OH }^{ - }\left( aq \right) \\ Base_{ 2 } \\ \left( Conjugate \ Base \right) \end{matrix}\)
The self-ionisation of water is called autoprotolysis.