developing metals (DM)

Question 1

What is oxidation in terms of electron transfer?

Answer 1

Oxidation is the loss of electrons.

Question 2

What is reduction in terms of electron transfer?

Answer 2

Reduction is the gain of electrons.

Question 3

What role do reducing agents play in redox reactions?

Answer 3

Reducing agents donate electrons to reduce another substance.

Question 4

What role do oxidising agents play in redox reactions?

Answer 4

Oxidising agents take electrons away from other substances, becoming reduced in the process.

Question 5

How do you balance redox equations?

Answer 5

Use H+, H2O, and e- to balance the redox equations.

Question 6

What is the purpose of an acid-base titration?

Answer 6

It is used to determine the exact amount of acid needed to neutralise a known quantity of alkali.

Question 7

What indicator is typically used in acid-base titrations, and what color change does it show?

Answer 7

Phenolphthalein is used, and it changes from colorless to pink.

Question 8

What is the goal of a redox titration?

Answer 8

A redox titration is used to determine how much oxidising agent is required to completely react with a known amount of reducing agent.

Question 9

Why is dilute sulfuric acid added in redox titrations?

Answer 9

It ensures there are plenty of H+ ions to facilitate the reduction of the oxidising agent.

Question 10

What are electrochemical cells, and how do they work?

Answer 10

Electrochemical cells consist of two different metals dipped in salt solutions of their own ions, connected by a wire and a salt bridge. Oxidation occurs at the negative electrode, and reduction happens at the positive electrode. Electrons flow through the wire from the more reactive metal to the less reactive one.

Question 11

In a zinc/copper electrochemical cell, what happens at each electrode?

Answer 11

Zinc is oxidized to Zn2+ (s) –> Zn2+ (aq) + 2e- at the negative electrode, and copper ions (Cu2+) are reduced to solid copper (Cu) at the positive electrode: Cu2+(aq) + 2e- –> Cu(s).

Question 12

How do you set up an electrochemical cell?

Answer 12

Clean electrodes with emery paper, remove grease using propanone, then connect them with a salt bridge made of filter paper soaked in salt solution, such as KCl.

Question 13

What is electrode potential?

Answer 13

Electrode potential is the potential difference between two half-cells that drives electron movement. A more negative electrode potential means the substance is more easily oxidized (acts as a reducing agent).

Question 14

What is the standard hydrogen electrode (SHE)?

Answer 14

The SHE is the reference electrode used in electrochemical cells, assigned a value of 0.00V. It has 1 mol/dm³ solutions, 298K (25°C) temperature, and 100 kPa pressure.

Question 15

How do you calculate the electrode potential of a cell?

Answer 15

The electrode potential of a cell is calculated as (E more +ve) - (E more -ve), and the value is always positive.

Question 16

What does a more reactive metal indicate about its electrode potential?

Answer 16

A more reactive metal has a more negative electrode potential, meaning it loses electrons more easily.

Question 17

What does a more reactive non-metal indicate about its electrode potential?

Answer 17

A more reactive non-metal has a more positive electrode potential, meaning it gains electrons more easily.

Question 18

How can the electrochemical series be used?

Answer 18

The electrochemical series predicts whether a reaction is feasible by comparing the electrode potentials of the substances involved.

Question 19

What is rusting, and what are the products formed?

Answer 19

Rusting is the corrosion of iron when exposed to oxygen and water, leading to the formation of iron (II) hydroxide, which is further oxidized to iron (III) hydroxide.

Question 20

How can rusting be prevented?

Answer 20

Rusting can be prevented by painting, greasing, or using the sacrificial method (zinc), which has a more negative electrode potential than iron.

Question 21

What is a transition metal?

Answer 21

A transition metal is a d-block element that can form at least one stable ion with an incomplete d sub-shell.

Question 22

What is the electron configuration rule for transition metals when ionizing?

Answer 22

Transition metals fill the 4s subshell before the 3d subshell and lose 4s electrons first when ionizing.

Question 23

What is the exception for chromium’s electron configuration?

Answer 23

Chromium has one electron in each orbital of the 3d subshell and one electron in the 4s subshell, which makes it more stable.

Question 24

What is the exception for copper’s electron configuration?

Answer 24

Copper prefers a full 3d subshell and just one electron in 4s, which is more stable.

Question 25

Why is scandium not considered a transition metal?

Answer 25

Scandium only forms Sc3+, which has an empty d subshell.

Question 26

Why is zinc not considered a transition metal?

Answer 26

Zinc only forms Zn2+, which has a full d subshell.

Question 27

What are the key properties of transition metals?

Answer 27

Transition metals have variable oxidation states, form colored ions in solution, and have closely spaced energy levels in the 4s and 3d orbitals, allowing them to gain or lose electrons in various oxidation states.

Question 28

What is a complex ion?

Answer 28

A complex ion is a central metal ion bonded to ligands via coordinate bonds.

Question 29

What is a coordinate (dative) bond?

Answer 29

A coordinate bond is formed when a ligand donates a pair of electrons to the central metal ion.

Question 30

What is a ligand?

Answer 30

A ligand is an atom, ion, or molecule that donates a pair of electrons to form a coordinate bond with a central metal ion. Monodentate ligands donate one lone pair, while bidentate ligands donate two lone pairs.

Question 31

What is the coordination number?

Answer 31

The coordination number is the number of coordinate bonds formed between a central metal ion and its surrounding ligands.

Question 32

What shapes can complex ions with 4 coordinate bonds take?

Answer 32

Complex ions with 4 coordinate bonds usually have a tetrahedral shape, but can sometimes be square planar (e.g., cisplatin).

Question 33

How do ligands affect the 3d subshell of the central metal ion?

Answer 33

Ligands split the 3d subshell into two energy levels. Electrons can absorb energy to jump to higher orbitals, and the size of the energy gap depends on factors like the central metal ion, oxidation state, ligands, and coordination number.

Question 34

Why do transition metal compounds have color?

Answer 34

Transition metal compounds have color because the 3d electrons absorb specific wavelengths of light as they jump between energy levels in the presence of ligands.

Question 35

What are the colors of some transition metal hydroxides when reacted with NaOH?

Answer 35

Copper: Pale blue to dark blue precipitate; Iron (II): Pale green to dark green; Iron (III): Yellow to orange.

Question 36

What is ligand substitution, and what is its effect on transition metal complexes?

Answer 36

Ligand substitution involves replacing one ligand with another, often resulting in a color change.

Question 37

How do transition metal catalysts work?

Answer 37

Transition metals act as catalysts by changing their oxidation states, transferring electrons, and speeding up reactions at lower temperatures and pressures.

Question 38

What is the process of heterogeneous catalysis?

Answer 38

In heterogeneous catalysis, molecules are adsorbed onto the catalyst surface, bonds are weakened, reactions occur, and products desorb from the catalyst.

Question 39

What makes a good heterogeneous catalyst?

Answer 39

A good heterogeneous catalyst has a strong enough attraction to hold molecules long enough to react but not so strong that it prevents desorption and blocks new reactants.

Question 40

How do transition metals work as homogeneous catalysts?

Answer 40

In homogeneous catalysis, the catalyst forms an intermediate, and the activation energy for the reaction with the intermediate is lower than that for direct reactant-to-product conversion.

Question 41

What is colorimetry, and how is it used?

Answer 41

Colorimetry measures the absorbance of light by a solution. The absorbance is used to determine the concentration of a substance, especially transition metal ions, by using a color filter and comparing absorbances to a calibration graph.

Question 42

How is a calibration graph used in colorimetry?

Answer 42

A calibration graph plots absorbance versus known concentrations. It allows you to find the concentration of an unknown substance by comparing its absorbance to the graph.

Question 43

What is visible spectroscopy, and how does it relate to transition metal complexes?

Answer 43

Visible spectroscopy measures light absorption by a solution and can be used to identify transition metal complexes based on their unique absorption spectra, which result from transitions between 3d orbitals.