Redox

Question 1

Trend in reactivity down group 1 metals

Answer 1

Increases as number of energy levels increases, atomic radius, less energy needed to remove an electron. Group 2 is less reactive than group 1.

Question 2

Describe voltaic cells

Answer 2

Convert from chemical energy to electrical energy (spontaneous process). The anode is negative, the cathode is positive. Electrons flow from the anode to cathode. Anode loses mass due to electron loss and cathode gains mass.

Question 3

What is the role of a salt bridge in a voltaic cell.

Answer 3

Allows the flow of ions in opposite directions so potential difference can be made.

Question 4

Cations go to….

Answer 4

Cations go to cathode, anions go to anode

Question 5

Electrolytic cells

Answer 5

Anode is positive (attracts anions) and cathode is negative (attracts cations). The products are full elements. Oxidation in anode, reduction in cathode.

Question 6

What is electrode cell potential?

Answer 6

The electromotive force (EMF) in a voltaic cell resulting in the movement of electrons from the anode (negative electrode) to the cathode (positive electrode) via the external circuit.

Question 7

What does the magnitude of electrode cell potential depend on?

Answer 7

The difference in the tendencies of two half cells to undergo reduction.

Question 8

Outline a standard hydrogen electrode

Answer 8

Used as a fixed reference point that acts as a standard for measurement of electrode cell potential. It consists of an inert platinum electrode in contact with concentrated HCl of 1.0moldm-3 and Hydrogen gas at 100 kPa and 298 K. When electrode submerge in acid, equilibrium set up between hydeogen gas and hydrogen ions. The electrode potential of SHE is assigned 0 so other half cells connected to it can be compared.

Question 9

What happens when SHE is connected to a half cell

Answer 9

The EMF generated is standard electrode potential of the half cell. If it is negative, electrons flow from the metal half cell to the hydrogen electrode. The hydrogen is reduced (cathode) and the metal is oxidized (anode). If it is positive, electrons flow from the hydrogen electrode to the metal half cell, so the hydrogen is oxidized (anode) and metal is reduced (cathode)

Question 10

Describe oxidation and reduction in voltaic cells

Answer 10

In a voltaic cell, the anode is oxidised (negative) and cathode is reduced (positive)