Oxidation Numbers

When $\mathrm{KBr}$ reacts with hydrazine, ${\mathrm{N}}_2{\mathrm{H}}_4$, nitrogen gas is evolved.

$2{\mathrm{KBrO}}_3+3{\mathrm{N}}_2{\mathrm{H}}_4\stackrel{ }{\to }2\mathrm{KBr}+3{\mathrm{N}}_2+6{\mathrm{H}}_2\mathrm{O}$

Explain, using oxidation numbers, why $2$ moles of ${\mathrm{KBrO}}_3$ react with $3$ moles of ${\mathrm{N}}_2{\mathrm{H}}_4$?

When $\mathrm{KBr}$ reacts with hydrazine, ${\mathrm{N}}_2{\mathrm{H}}_4$, nitrogen gas is evolved.

$2{\mathrm{KBrO}}_3+3{\mathrm{N}}_2{\mathrm{H}}_4\stackrel{ }{\to }2\mathrm{KBr}+3{\mathrm{N}}_2+6{\mathrm{H}}_2\mathrm{O}$

Deduce the oxidation number change for each nitrogen atom when ${\mathrm{N}}_2{\mathrm{H}}_4$ is converted to ${\mathrm{N}}_2$.

When $\mathrm{KBr}$ reacts with hydrazine, ${\mathrm{N}}_2{\mathrm{H}}_4$, nitrogen gas is evolved.

$2{\mathrm{KBrO}}_3+3{\mathrm{N}}_2{\mathrm{H}}_4\stackrel{ }{\to }2\mathrm{KBr}+3{\mathrm{N}}_2+6{\mathrm{H}}_2\mathrm{O}$

Deduce the oxidation number change of the bromine atom when ${\mathrm{KBrO}}_3$ is converted to $\mathrm{KBr}$.

The compound ${\mathrm{KBrO}}_3$ decomposes when heated:

$2{\mathrm{KBrO}}_3\stackrel{ }{\to }2\mathrm{KBr}+3{\mathrm{O}}_2$

State the oxidation number of bromine in $\mathrm{KBr}$.

The compound ${\mathrm{KBrO}}_3$ decomposes when heated:

$2{\mathrm{KBrO}}_3\stackrel{ }{\to }2\mathrm{KBr}+3{\mathrm{O}}_2$

State the oxidation number of bromine in ${\mathrm{KBrO}}_3$.

When a salt containing iodide ions is warmed with concentrated sulphuric acid and ${\mathrm{MnO}}_2$, iodine is evolved:

$2{\mathrm{I}}^{-}+{\mathrm{MnO}}_2+6{\mathrm{H}}^{+}+2{{\mathrm{SO}}_4}^{2-}\stackrel{ }{\to }{\mathrm{I}}_2+{\mathrm{Mn}}^{2+}+2{{\mathrm{HSO}}_4}^{-}+2{\mathrm{H}}_2\mathrm{O}$

Deduce the oxidation number of $\mathrm{S}$ in the ${{\mathrm{SO}}_4}^{2-}$ ion.

Iodine, ${\mathrm{I}}_2$, reacts with thiosulphate ions ${\mathrm{S}}_2{{\mathrm{O}}_3}^{2-}$, to form iodide ions, ${\mathrm{I}}^{-}$, and tetrathionate ions, ${\mathrm{S}}_4{{\mathrm{O}}_6}^{2-}$as ${\mathrm{I}}_2+2{\mathrm{S}}_2{{\mathrm{O}}_3}^{2-}\stackrel{ }{\to }2{\mathrm{I}}^{-}+{\mathrm{S}}_4{{\mathrm{O}}_6}^{2-}$. State the oxidation number of each sulphur atom in a ${\mathrm{S}}_4{{\mathrm{O}}_6}^{2-}$ ion.

Iodine, ${\mathrm{I}}_2$, reacts with thiosulphate ions ${\mathrm{S}}_2{{\mathrm{O}}_3}^{2-}$, to form iodide ions, ${\mathrm{I}}^{-}$, and tetrathionate ions, ${\mathrm{S}}_4{{\mathrm{O}}_6}^{2-}$as ${\mathrm{I}}_2+2{\mathrm{S}}_2{{\mathrm{O}}_3}^{2-}\stackrel{ }{\to }2{\mathrm{I}}^{-}+{\mathrm{S}}_4{{\mathrm{O}}_6}^{2-}$. State the oxidation number of each sulphur atom in a ${\mathrm{S}}_2{{\mathrm{O}}_3}^{2-}$ ion.

Aluminium reacts with hydrochloric acid to form aluminium chloride, ${\mathrm{AlCl}}_3$, and hydrogen. This is a redox reaction. Deduce the change in oxidation number when a hydrogen ion turns into a hydrogen atom.

The unbalanced equation for the reaction of sulphur dioxide with bromine is as shown below:

${\mathrm{SO}}_2+{\mathrm{Br}}_2+{\mathrm{H}}_2\mathrm{O}\stackrel{ }{\to }{{\mathrm{SO}}_4}^{2-}+{\mathrm{Br}}^{-}+{\mathrm{H}}^{+}$

State the change in oxidation number for each bromine atom.

The unbalanced equation for the reaction of sulphur dioxide with bromine is as shown below:

${\mathrm{SO}}_2+{\mathrm{Br}}_2+{\mathrm{H}}_2\mathrm{O}\stackrel{ }{\to }{{\mathrm{SO}}_4}^{2-}+{\mathrm{Br}}^{-}+{\mathrm{H}}^{+}$

State the change in oxidation number for each $\mathrm{S}$ atom.

The unbalanced equation for the reaction of sulphur dioxide with bromine is as shown below:

${\mathrm{SO}}_2+{\mathrm{Br}}_2+{\mathrm{H}}_2\mathrm{O}\stackrel{ }{\to }{{\mathrm{SO}}_4}^{2-}+{\mathrm{Br}}^{-}+{\mathrm{H}}^{+}$

State the oxidation number of bromine in ${\mathrm{Br}}^{-}$.

The unbalanced equation for the reaction of sulphur dioxide with bromine is as shown below:

${\mathrm{SO}}_2+{\mathrm{Br}}_2+{\mathrm{H}}_2\mathrm{O}\stackrel{ }{\to }{{\mathrm{SO}}_4}^{2-}+{\mathrm{Br}}^{-}+{\mathrm{H}}^{+}$

State the oxidation number of bromine in ${\mathrm{Br}}_2$.

The unbalanced equation for the reaction of sulphur dioxide with bromine is as shown below:

${\mathrm{SO}}_2+{\mathrm{Br}}_2+{\mathrm{H}}_2\mathrm{O}\stackrel{ }{\to }{{\mathrm{SO}}_4}^{2-}+{\mathrm{Br}}^{-}+{\mathrm{H}}^{+}$

State the oxidation number of sulphur in ${{\mathrm{SO}}_4}^{2-}$.

The unbalanced equation for the reaction of sulphur dioxide with bromine is as shown below:

${\mathrm{SO}}_2+{\mathrm{Br}}_2+{\mathrm{H}}_2\mathrm{O}\stackrel{ }{\to }{{\mathrm{SO}}_4}^{2-}+{\mathrm{Br}}^{-}+{\mathrm{H}}^{+}$

State the oxidation number of sulphur in ${\mathrm{SO}}_2$.

Calcium reacts with cold water to form calcium hydroxide, $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$, and hydrogen, ${\mathrm{H}}_2$. State the oxidation number of hydrogen in hydrogen gas.

Calcium reacts with cold water to form calcium hydroxide, $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$, and hydrogen, ${\mathrm{H}}_2$. State the oxidation number of hydrogen in water.

State the oxidation number of calcium in calcium hydroxide.

Calcium reacts with cold water to form calcium hydroxide, $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$, and hydrogen, ${\mathrm{H}}_2$. State the oxidation number of calcium in calcium metal.

Look at the equation: ${\mathrm{Cr}}_2{{\mathrm{O}}_7}^{2-}+2{\mathrm{H}}^{+}+3{\mathrm{SO}}_2\stackrel{ }{\to }2{\mathrm{Cr}}^{3+}+{\mathrm{H}}_2\mathrm{O}+3{{\mathrm{SO}}_4}^{2-}$. Which one of these statements about the oxidation number changes is correct?