(i) The addition of oxygen to a substance is called oxidation.
(ii) The removal of hydrogen from a substance is also called oxidation.
(i) The addition of hydrogen to a substance is called reduction.
(ii) The removal of oxygen from a substance is also called reduction.
(i) The substance which gives oxygen for oxidation is called an oxidizing agent.
(ii) The substance which removes hydrogen is also called an oxidizing agent.
(i) The substance which gives hydrogen for reduction is called a reducing agent.
(ii) The substance which removes oxygen is also called a reducing agent.
When copper oxide is heated with hydrogen, then copper metal and water are formed :
CuO + H2→ Cu + H2O
|(i) Substance oxidized: H2|
(ii) Substance reduced: CuO
(iii) Oxidising agent: CuO
(iv) Reducing agent: H2
(i) The shiny brown coloured element X is copper metal (Cu).
(ii) When copper metal is heated in air, it forms a black coloured compound copper oxide. So, the black coloured compound is copper oxide or copper (II) oxide, CuO.
1.What is a redox reaction? When a magnesium ribbon burns in air with a dazzling flame and forms white ash, is magnesium oxidized or reduced? Why?
Ans: The reactions in which oxidation (loss of electrons) and reduction (gain of electrons) take place simultaneously are called redox reactions.
Magnesium is getting oxidized because it is losing electrons to form Mg2+ and oxygen is gaining electrons to form O2-, therefore it is getting reduced.
2. You are given the following chemical equation: Mg (s) + CuO (s) MgO (s) + Cu (s)
This equation represents :
(a) decomposition reaction as well as displacement reaction
(b) combination reaction as well as double displacement reaction
(c) redox reaction as well as displacement reaction
(d) double displacement reaction as well as a redox reaction
ANS: Redox reaction as well as displacement reaction.
3. The process of respiration is :
(a) an oxidation reaction which is endothermic
(b) a reduction reaction which is exothermic
(c) a combination reaction which is endothermic
(d) an oxidation reaction which is exothermic
ANS: An oxidation reaction that is exothermic.
4. In the reaction represented by the following equation: CuO (s) + H2 (g) o Cu (s) + H2O (l)
(a) name the substance oxidized (b) name the substance reduced
(c) name the oxidizing agent (d) name the reducing agent
ANS: (a) H2