Reactivity 3.2 — SL Part 1 Flashcards
What is the oxidation state of an element in its pure form?
The oxidation state of a pure element is always 0.
In a compound, what is the general oxidation state of oxygen?
The general oxidation state of oxygen in a compound is -2.
How can you identify the oxidised species in a chemical reaction?
The oxidised species is the one that increases its oxidation state during the reaction, indicating it has lost electrons.
How can you identify the reducing agent in a redox reaction?
The reducing agent is the substance that gets oxidised, meaning it loses electrons and causes the reduction of another species.
What is the purpose of balancing redox reactions?
Balancing redox reactions ensures that the law of conservation of mass and charge is obeyed, by making sure the number of atoms and the charge are the same on both sides of the equation.
How are oxygen atoms balanced in half-reactions for redox equations in acidic solutions?
Oxygen atoms are balanced by adding water (H₂O) molecules to the side lacking oxygen.
How do you balance the hydrogen atoms in redox reactions occurring in acidic solutions?
Hydrogen atoms are balanced by adding hydrogen ions (H⁺) to the side lacking hydrogen.
What indicates that a species has been reduced in a redox reaction?
A species has been reduced if its oxidation state decreases, indicating it has gained electrons.
What is the difference between an oxidising agent and a reducing agent in a redox reaction?
An oxidising agent gains electrons and is reduced, while a reducing agent loses electrons and is oxidised.
What determines the ease of oxidation of metals, and what is a displacement reaction?
The ease of oxidation of metals is determined by their ability to lose electrons and form positive ions. In displacement reactions, a more reactive metal can displace a less reactive metal from its compound. Example: Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s).
How can you determine the reactivity series of metals from displacement reactions?
By observing whether a metal can displace another from its aqueous ion solution. Metals that can displace others are more reactive. Reactivity decreases in the order Zn > Pb > Cu > Ag based on displacement reactions.
How does metal reactivity change across a period and down a group in the periodic table?
Across a period, reactivity decreases due to increasing effective nuclear charge, making valence electrons harder to remove. Down a group, reactivity increases as valence electrons are farther from the nucleus, making them easier to remove.
What is the trend in the reactivity of halogens, and how can it be determined?
The reactivity of halogens decreases down the group. This can be determined through displacement reactions with halide ions, where a more reactive halogen displaces a less reactive one from its compound.
What general equation describes the reaction of metals with dilute acids, and what are the products?
The general equation is: acid + metal → salt + hydrogen gas. Reactive metals such as Zn, Mg, and Fe react with dilute acids (HCl, H2SO4) to produce a salt and hydrogen gas.
How is hydrogen gas produced in reactions between metals and acids?
Hydrogen gas is produced when reactive metals, such as magnesium or zinc, react with dilute acids. The metal is oxidized, forming metal ions, and hydrogen ions from the acid are reduced to hydrogen gas (H2).
