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.

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.
\(8LiH+{ Al }_{ 2 }{ Cl }_{ 6 }\longrightarrow 2LiAl{ H }_{ 4 }+6LiCl\)

\(\because \) 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

\(Given,\ { V }_{ 1 }=2L;{ V }_{ 2 }=?\)
\({ T }_{ 2 }=(26.1+273)K=299.1K\)
\( { T }_{ 1 }=(23.4+273)K=296.4K\)
\(According \ to \ Charles \ law,\)
\( \frac { { V }_{ 1 } }{ { T }_{ 1 } } =\frac { { V }_{ 2 } }{ { T }_{ 2 } } or{ V }_{ 2 }=\frac { { V }_{ 1 }{ T }_{ 2 } }{ T_{ 1 } } \)
\(on \ substituting \ the \ corresponding \ values,\ we \ get\)
\(\Rightarrow \ { V }_{ 2 }=\frac { 2L\times 299.1K }{ 296.4K } =2.018L\)

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.

\(\triangle x\times \triangle P=\frac { h }{ 4\pi } ,\ As \ \triangle x=\triangle P\) 
\( \therefore { \left( \triangle P \right) }^{ 2 }=\frac { h }{ 4\pi } or\quad \triangle P=\sqrt { \frac { h }{ 4\pi } } or \ m\times \triangle v=\sqrt { \frac { h }{ 4\pi } } \)
\( or \ \triangle v=\frac { 1 }{ m } \sqrt { \frac { h }{ 4\pi } } =\frac { 1 }{ 9.11\times { 10 }^{ -31 } } \times \sqrt { \frac { 6.626\times { 10 }^{ -34 } }{ 4\times 3.14 } }\)
\( =\frac { 0.726\times { 10 }^{ -17 } }{ 9.11\times { 10 }^{ -31 } } =7.89\times { 10 }^{ 12 }{ ms }^{ -1 }\)
Thus, uncertainty in velocity is greater than the velocity of light which is impossible. Thus, the two uncertainties cannot be equal in magnitude.