module 2 - redox

Question 1

in oxidation numbers, does the number or the sign come first?

Answer 1

the sign

Question 2

what’s the oxidation number of F in a compound?

Answer 2

-1

Question 3

what’s the oxidation number of H in metal hydrides? give examples of 2 metal hydrides!

Answer 3

> -1

> NaH, CaH2

Question 4

what’s the oxidation number of O in peroxides? Give an example of a peroxide?

Answer 4

> -1

> - H2O2

Question 5

what’s the oxidation number of O when it’s bonded to F?

Answer 5

+2 e.g. in F2O

Question 6

in a compound, what must the sum of the oxidation numbers be equal to?

Answer 6

the total charge

Question 7

say the 3 steps in working out oxidation numbers in a compound/ ion?

Answer 7

1) assign any ox numbers with rules
2) work out overall charge
3) work out unknown numbers based on that everything should add up to overall charge

Question 8

what are roman numerals used in, for redox?

Answer 8

used in names of compounds that have elements that form ions with different charges

Question 9

what does the roman numerals show?

Answer 9

the oxidation number (state) of the element with no sign

Question 10

what is the formula and ox number for iron(II)?

Answer 10

Fe 2+ so, ox = +2

Question 11

what are the modern names for nitrite and nitrate? what are these names based on?

Answer 11

• nitrate (III)
• nitrate (v)
• the oxidation number of the nitrogen

Question 12

what is oxidation and reduction in terms of oxygen reactions?

Answer 12

• addition or removal of oxygen

Question 13

in the reaction CuO + H2 —> Cu + H2O , whats been oxidised? and reduced?

Answer 13

• hydrogen is oxidised by gaining oxygen

- copper oxide is reduced by losing oxygen

Question 14

what’s a redox reaction?

Answer 14

a reaction involving reduction and oxidation

Question 15

what are the real definitions of reduction and oxidation in terms of electrons?

Answer 15

red = gain of electrons
ox = loss of electrons
(OILRIG innit)

Question 16

in this reaction, what gains and what loses electrons?

2Fe + 3Cl2 -> 2FeCl3 give ionic equations as proof.

Answer 16

• iron lost electrons= oxidised:
  2Fe -> 2Fe 3+ + 6e (lost neg thoughts and got positive charge)
• chlorine got electrons = reduction:
  3Cl2 + 6e- –> 6cl-
  (was 3cl- then 6cl-, got more bad thoughts)

Question 17

what is reduction and oxidation in terms of oxidation number?

Answer 17

r = decrease in ox number
ox = increase in ox num

Question 18

metal + acid = ?

Answer 18

salt + hydrogen

Question 19

what type of acids undergo redox reactions with some metals?

Answer 19

dilute acids

Question 20

give the equation for the reaction of zinc with HCl?

Answer 20

Zn(s) + 2HCl (aq) —> ZnCl2(aq) + H2 (g)