equations

Question 1

thermal decomposition:
MCO3 (group 2 metal carbonate) —heat—>

Answer 1

MO + CO2

Question 2

MO (group 1/2 metal oxide) + H2O —>

Answer 2

MOH (metal hydroxide)

Question 3

M(OH)2 (group 2 metal) —>

Answer 3

MO + H2O

Question 4

what is the manganate half equation?

Answer 4

MnO4- + 8H+ + 5e- —> Mn2+ + 4H2O
purple —-> pink

Question 5

what is the dichromate half equation?

Answer 5

Cr2O7 2- + 6e- + 14H+ —> 2Cr3+ + 7H2O
orange —> green

Question 6

what is the thiosulfate half equation?

Answer 6

2S2O3 2- —> S4O6 2- + 2e-

Question 7

I2 + 2e- —>

Answer 7

2I-

Question 8

what equation is it if a question mentions an observation of white precipitate and brown solution?

Answer 8

Cu2+ + 4I- —> CuI + I2

Question 10

what is the equation for aluminium acting as a base?

Answer 10

Al2O3 + 6HCl —> 2AlCl3 + 3H2O

Question 11

what is the equation for aluminium acting as an acid?

Answer 11

Al2O3 + 3H2O + 2NaOH —> 2Na[Al(OH)4]

Question 12

what is the equation for lead acting as a base?

Answer 12

PbO + 2HNO3 —> Pb(NO3)2 + 2H2O

Question 13

what is the equation for lead acting as an acid?

Answer 13

PbO + H2O + 2NaOH —> Na2[Pb(OH)4]

Question 14

what is the equation for the reaction of lead with NaOH?

Answer 14

Pb2+ (aq) + 2OH- (aq) —> Pb(OH)2 (s)
forms white ppt

Question 15

what is the equation for the reaction of lead with excess NaOH?

Answer 15

• white ppt redissolves
• Pb(OH)2 (s) + 2OH- (aq) —> [Pb(OH)4]2-
  forms ‘plumbate’ ion

Question 16

what is the equation for the reaction of aluminium with NaOH?

Answer 16

Al3+ (aq) + 3OH- (aq) —> Al(OH)3 (s)
forms white ppt

Question 17

what is the equation for the reaction of aluminium with excess NaOH?

Answer 17

Al(OH)3 (s) + OH- (aq) —> [Al(OH)4]-
forms ‘aluminate’ ion

Question 18

inert pair effect:
Fe2O3 + 3CO —>

Answer 18

2Fe + 3CO2

Question 19

PbO2 + 4HCl —>

Answer 19

PbCl2 + Cl2 + 2H2O

Question 20

what is the equation of CO2 as an acidic oxide?

Answer 20

CO2 + H2O —> H2CO3 (weak acid - partial dissociation)

Question 21

partial dissociation of H2CO3:

Answer 21

H2CO3 ⇌ H+ + HCO3- ⇌ 2H+ + CO3 2-

Question 22

Pb2+ (aq) + 2Cl- (aq) —>

Answer 22

PbCl2
white ppt

Question 23

Pb2+ (aq) + 2I- (aq) —>

Answer 23

PbI2 (s)
bright/canary yellow

Question 24

what is the equation of SiCl4 with water?

Answer 24

SiCl4 + 2H2O —> SiO2 + 4HCl
white fumes produced

Question 25

what is the equation of CCl4 with water?

Answer 25

CCl4 + H2O —> NO REACTION
two immiscible layers

Question 26

what is the disproportionation reaction of chlorine to form bleach?

Answer 26

Cl2 + 2NaOH —> NaCl + NaClO + H2O

(cold NaOH)

Question 27

what is the disproportionation reaction of chlorine to form weed killer?

Answer 27

Cl2 + 6NaOH —> 5NaCl + NaClO3 + 3H2O
(hot NaOH)

Question 28

what is the disproportionation reaction of chlorine with water?

Answer 28

Cl2 + H2O —> HCl + HClO

Question 29

[Cu(H2O)6]2+ + 2OH- —>

Answer 29

[Cu(OH)2(H2O)4] + 2H2O
blue solution —> pale blue ppt

Question 30

[Co(H2O)6]2+ + 2OH- —>

Answer 30

[Co(OH)2(H2O)4] + 2H2O
pink solution —> blue ppt

Question 31

[Fe(H2O)6]2+ + 2OH- —>

Answer 31

[Fe(OH)2(H2O)4] + 2H2O
pale green solution —> pale green/green ppt

Question 32

[Fe(H2O)6]3+ + 3OH- —>

Answer 32

[Fe(OH)3(H2O)3] + 3H2O
yellow solution —> orange/brown ppt

Question 33

[Cr(H2O)6]3+ + 3OH- —>

Answer 33

[Cr(OH)3(H2O)3] + 3H2O
green solution —> grey-green ppt

Question 34

[Cr(OH)3(H2O)3] + 3OH- —>

Answer 34

[Cr(OH)6]3- + 3H2O
grey-green ppt to dark green solution

Question 35

[Cu(H2O)6]2+ + 4Cl- —>

Answer 35

[CuCl4]2- + 6H2O
blue —> yellow-green solution

Question 36

[Co(H2O)6]2+ + 4Cl- —>

Answer 36

[CoCl4]2- + 6H2O
pink —> blue

Question 37

[Cu(H2O)6]2+ + 2NH3 —>

Answer 37

[Cu(OH)2(H2O)4] + 2NH4+
blue —> pale blue ppt

Question 38

[Cu(OH)2(H2O)4] + 4NH3 —>

Answer 38

[Cu(NH3)4(H2O)2]2+ + 2H2O + 2OH-
blue —> deep royal blue