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Chemistry A level Edexcel > Redox > Flashcards

Flashcards in Redox Deck (16)
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1
Q

Define oxidation

A

Loss of electrons, increase in oxidation number, gain of oxygen and loss of hydrogen

2
Q

Define reduction

A

Gain of electrons, decrease in oxidation number, loss of oxygen and gain of hydrogen

3
Q

Define anode

A

The electrode where oxidation takes place

4
Q

Define cathode

A

The electrode where reduction takes place

5
Q

Define oxidising agent

A

A species that oxidises another species by removing 1+ electrons, and itself being reduced.

6
Q

Define reducing agent

A

A species that reduces another species by adding 1+ electrons, and itself is oxidised

7
Q

Which direction do electrons flow?

A

From anode to cathode (oxidation half cell to reduction half cell)

8
Q

Describe the standard hydrogen electrode

A

A platinum foil immersed in 1moldm^-3 HCl, enclosed in a tube containing hydrogen gas at standard pressure

9
Q

What are the standard conditions?

A

298k, 100kPa (1atm) 1moldm^-3 and elements in their standard states

10
Q

What is OILRIG?

A
Oxidation
Is
Loss (of electrons)
Reduction
Is
Gain (of electrons)
11
Q

What are the rules for assigning oxidation numbers?

A

Oxidation number of atoms in elements is always 0

The more electronegative element in the substance has the negative oxidation number and the less electronegative element has the positive oxidation number

Fluorine is always -1

Hydrogen is always +1, except in metal hydrides where it is -1

Oxygen is always -2, except in peroxide where it is -1, and in OF2 it is +2 as fluorine is more electronegative

In neutral molecules the sum of the oxidation numbers is 0

In ions the sum of the oxidation numbers is equal to the charge

12
Q

What is the standard cell potential?

A

Voltage measured under standards conditions when a half cell is connected to a standard hydrogen electrode. It tells us how readily a substance releases electrons relative to hydrogen

E(cell) = reduction half cell - oxidation half cell

13
Q

What is a salt bridge?

A

Porous substance soaked in a solution of an inert, strong electrolyte. The salt ions flow through the bridge to complete the cell and balance charges in solutions.

Eg. Filter paper soaked in KNO3

14
Q

What is an electrochemical cell?

A

Produces electricity from a chemical reaction (combination of 2 half cells)

15
Q

What is a storage cell?

A

(Battery) a cell that can be recharged when the current is passed in the opposite way to the current generated by a chemical reaction in the cell.

16
Q

What is a fuel cell?

A

A cell used to harness electricity from a chemical reaction (fuel + oxygen). Chemicals are stored separately outside the cell and fed in when electricity is required