RedOx

Question 1

When is the oxidation number 0, using examples?

Answer 1

In any uncombined element- e.g H2 or Br2- as there is no transfer of electrons

Question 2

What is the sum of all the oxidation numbers in an overall neutral compound?

Answer 2

Zero- it has no overall charge

Question 3

What acronym can be used to recall the priority order of different elements in changing oxidation state?

Answer 3

Under- uncombined elements
My- Metals
Face- Fluorine
Here’s- Hydrogen
Our- Oxygen
Chin- Chlorine

so, chlorine is most likely to change oxidation state and uncombined elements will never change away from their regular oxidation state

Question 4

Oxidation state of sulfur in SO4 2-

Answer 4

+6
•oxygen higher in priority so -8
•difference between -2 and -8 is +6, so sulfur +6

Question 5

What element’s oxidation state is shown in systematic names?

Answer 5

The element which has an unusual oxidation state charge- e.g chlorine or transition metals
(the one that is worked out)

Question 6

What is the systematic name for FeCl3?

Answer 6

Iron (III) Choride

Question 7

What is the systematic name for NaNO2?

Answer 7

Sodium nitrite (III)

Question 8

Oxidation state of S in Na2S2O8?

Answer 8

+7
•O= -16
•Na= +2
So 14 divided by 2 (2 S atoms) =7

Question 9

What is the oxidation state of F in F2O?

Answer 9

-1

Fluorine is more electronegative than oxygen

Question 10

What is meant by a redox reaction?

Answer 10

When both reduction and oxidation occur

Question 11

Describe what oxidation and reduction are (4)

Answer 11

• Oxidation: the loss of electrons, increase in oxidation number
• Reduction: the gain of electrons, decrease in oxidation number

Question 12

Compare oxidising and reducing agents. (3)

Answer 12

• An oxidising agent is itself reduced (takes electrons) and oxidises other species
• A reducing agent is itself oxidised (loses electrons) and reduces other species (giving them electrons)

Question 13

Describe how to write a redox equation out from two half equations (3)

Answer 13

• Multiply the half equation(s) by a factor so that the number of electrons in each half-equation is the same
• Add the two half-equations together
• The electrons should cancel out, leaving the redox equation

Question 14

What acronym can be remembered to construct half-equations? (4)

Answer 14

•Every- balance the ELEMENT being oxidised or reduced first
•One- balance the OXIDATION NUMBERS, using electrons.
•Can- balance the CHARGE using H+ (acidic solution) or OH- (alkaline solution)
•Win- add water to balance the O and H

Question 15

What is the systematic name for TiCl4?

Answer 15

Titanium (IV) Chloride

we know Cl is -1, so 4x-1 =-4 so Ti must have an OSC of +4 here