Question

Practice Predicting Redox Reactions • Write molecular and net ionic equations for each of the following • Also indicate which substance is oxidized and which reduced in each reaction . Finally, indicate the oxidation states of the elements before and after reaction 1) aluminum metal + aqueous silver nitrate → Hi (5) + AgNO₃ cag Ag (s) + Al(aq) + Nos 2) magnesium metal + hydrobromic acid → 3) lithium metal + oxygen gas → 4) combustion of pentane (CSH12) ► 5) silver metal + aqueous calcium nitrate →

Answer 1

1.

Molecular equation

Al (s) + 3 AgNO₃$\to$ 3 Ag + Al(NO₃)₃

Net Ionic equation

Al (s) + 3 Ag⁺ (aq) $\to$ 3Ag + Al³⁺ (aq)

Aluminium is oxidised and Silver ion is reduced.

Oxidation state of elements

Element	before	after
Al	0	+3
Ag	+1	0

2.

Molecular equation

Mg (s) + 2HBr (aq) $\to$ MgBr₂ (aq) + H₂ (g)

Net ionic equation

Mg (s) + 2 H⁺ (aq)  $\to$ Mg²⁺ (aq) + H₂ (g)

Mg is oxidized and H⁺ is reduced .

Oxidation state are given below

Element	before	after
Mg	0	+2
H	+1	0

3.

Molecular equation

2 Li (s) + _{$\frac{1}{2}$} O₂ (g)  $\to$ Li₂O (s)

Net ionic equation

2 Li + _{$\frac{1}{2}$} O₂$\to$ 2 Li⁺ + O^2-

Li is oxidised and oxygen is reduced.

Oxidation state are given below

Element	before	after
Li	0	+1
O	0	-2

4.

Molecular equation

C₅H₁₂ (l)+ 8 O₂ (g)  $\to$ 5 CO₂ (g) + 6 H₂O (l)

No ionic equation.

Carbon is oxidised, oxygen is reduced.

Oxidation states are given below.

Element	before	after
C	-4	+4
O	0	-2
H	+1	+1

5)

Molecular equation.

Ag (s) + Ca(NO₃)₂ (aq) $\to$ 2 AgNO₃(aq) + Ca (s)

Ionic equation

Ag (s) + Ca²⁺ (aq) $\to$ 2Ag⁺ (aq) + Ca (s)

Ag is oxidised

Ca²⁺ is reduced.

Oxidation states are given below.

Element	before	after
Ag	0	+1
Ca	+2	0