Substances From The Earth Part3 Flashcards
What happens in terms of oxygen in an oxidation and reduction reaction?
Oxidation: The gain of oxygen by a substance.
Reduction: The loss of oxygen by a substance.
Describe the reaction of magnesium with oxygen.
• 2Mg(s) + 02(g) → 2MgO(s)
• Magnesium gains oxygen (oxidised), and oxygen loses oxygen (reduced).
• Magnesium is the reducing agent, and oxygen is the oxidising agent.
Describe the reaction of lead (Il) oxide with carbon.
• 2PbO(s) + C(s) → 2Pb(s) + CO2(g)
• Lead (II) oxide loses oxygen (reduced), and carbon gains oxygen (oxidised).
• Carbon is the reducing agent, and lead (Il) oxide is the oxidising agent.
How do you identify oxidising and reducing agents in a redox reaction?
• Oxidising agent: The substance that gains oxygen (gets reduced).
• Reducing agent: The substance that loses oxygen (gets oxidised).
Describe the reaction where hydrogen is added to ethene.
• C2Ha(g) + H2(g) → C2H6(g)
• Ethene (C2H4) gains hydrogen to form ethane (CHs), so it is reduced.
• Ethene is the oxidising agent, and hydrogen is the reducing agent.
Describe the reaction where hydrogen is removed from hydrogen sulfide.
•H2S(g) + Cl(g) → S(s) + 2HCl(g)
• Hydrogen sulfide (HS) loses hydrogen and is oxidised to sulfur (S).
• Hydrogen sulfide is the reducing agent, and chlorine is the oxidisin agent as it gains hydrogen.
How do you identify the oxidising and reducing agents when hydrogen is involved?
• Oxidising agent: The substance that gains hydrogen and is reduced.
• Reducing agent: The substance that loses hydrogen and is oxidised.
What happens in the reaction C2H4(g) +
H2(g) → C2Hь(g)?
.
• Ethene (CHa) gains hydrogen and becomes ethane (CHo), so it is reduced.
• Ethene is the oxidising agent, and hydrogen is the reducing agent.
What happens in the reaction HeS(g) +
C|(g) → S(s) + 2HC|(g)?
• Hydrogen sulfide (HS) loses hydrogen and is oxidised to sulfur (S).
• Hydrogen sulfide is the reducing agent, and chlorine is the oxidising agent as it gains hydrogen.
How can redox reactions be interpreted in terms of electron transfer?
• Oxidation: The process of losing electrons.
• Reduction: The process of gaining electrons.
• Oxidising agent: The electron acceptor.
• Reducing agent: The electron donor.
What happens in the reaction 2Mg(s) +
02(g) → 2MgO(s)?
• Magnesium (Mg): Loses electrons to form
Mg? ions, so it is oxidised.
• 2Mg → 2Mg2++ 4e
• Oxygen (02): Gains electrons to form O- ions, so it is reduced.
• 02+4e → 202-
• Magnesium is the reducing agent because it donates electrons.
• Oxygen is the oxidising agent because it accepts electrons.
What happens in the reaction 2Na(s) +
C|(g) → 2NaCl(s)?
• Sodium (Na): Loses electrons to form Na* ions, so it is oxidised.
• 2Na → 2Nat + 2e-
• Chlorine (Clz): Gains electrons to form Clions, so it is reduced.
• Cla + 2e* → 2Cl
Sodium is the reducing agent because it
donates electrons.
Chlorine is the oxidising agent because it
accepts electrons.
What is the oxidation number of elements in their free state?
• All elements in the free state (uncombined with any other elements) have an oxidation number of zero.
• Examples: Fe(s), Na(s), S(s), C(s), C/(g).
What is the oxidation number of simple ions?
• The oxidation number of a simple ion is the same as the charge on the ion.
• Examples: Na* (oxidation number +1), CI-(oxidation number -1).
Flashcard 45: Oxidation
What is the oxidation number of simple ions?
• The oxidation number of a simple ion is the same as the charge on the ion.
• Examples: Na* (oxidation number +1), CI-(oxidation number -1).
Flashcard 45: Oxidation
What are the oxidation numbers of Group 1, 2, and 3 metal ions?
• Group 1: +1 (e.g., Na, K).
• Group 2: +2 (e.g., Ca?, Mgz).
• Group 3: +3 (e.g., Als+).
What is the oxidation number of Group 7 non-metal ions?
• Group 7: -1 (e.g., Cl, Br).
What is the oxidation number of hydrogen in different compounds?
• +1 when combined with non-metals (e.g., hydrogen chloride, HCI).
• -1 when combined with metals (e.g., sodium hydride, NaH).
What is the oxidation number of the oxide ion (O2-)?
• The oxidation number of the oxide ion is always -2.
How is the oxidation number of a polyatomic ion determined?
• The oxidation number of a polyatomic ion is the same size and sign of the charge of the polyatomic ion.
• Example: The sulfate ion (SO,?*) has an oxidation number of -2.
How do oxidation and reduction occur in the reaction 2Na(s) + C|(g) → 2NaCl(s)?
• Electron transfer:
• Sodium loses electrons to form Nations:
2Na → 2Na* + 2e (oxidation).
• Chlorine gains electrons to form Clions: Cla
+ 2e → 2Cl (reduction).
• Oxidation numbers:
• Sodium changes from O to +1 (oxidation).
• Chlorine changes from O to -1 (reduction).
What happens when coke burns with oxygen in the blast furnace?
• The coke (carbon) reacts with oxygen to produce carbon dioxide:
• C(s) + 02(g) → COz(g).
• In this reaction, carbon is oxidised (it gains oxygen).
How do oxidation numbers change in the reaction between iron ore and carbon monoxide in the blast furnace?
• In Fe203 + 3CO → 2Fe + 3C02:
• Iron: The oxidation number decreases from +3 (in FezO3) to 0 (in Fe), so iron is reduced.
• Carbon: The oxidation number increases from +2 (in CO) to +4 (in COz), so carbon is oxidised.
What is a net ionic equation?
A net ionic equation represents the actual chemical reaction that occurs in a solution, showing only the ions and compounds that are involved in the reaction. Spectator ions, which do not take part in the reaction, are not included in the net ionic equation.
