Things I Keep Forgetting

Question 1

What can react with added acid to maintain ph

Answer 1

Proton acceptor
-weak base (basic buffer)
-strong conjugate base (Acidic buffer)

Question 2

What can react with added base to maintain ph

Answer 2

Proton donor
-weak acid (acidic buffer)
-strong conjugate acid salt (basic buffer)

Question 3

Why is buffer solution present

Answer 3

Interacted weak acid and salt of weak acid therefore ph change is more gradual.

Question 4

Why does diluting buffer with water keep ph unchanged

Answer 4

Affects both [HA] and [A-] equally
Equal mole of H+ and OH- added

Question 5

Best oxidising agent

Answer 5

Best at accepting e- therefore highest E0 value on left hand side

Question 7

Best reducing agent

Answer 7

Best at donating e- therefore lowest E0 value and bottom most -ve value

Question 8

Will H+ with E0 of 0.00 V react with Zn with E0 of -0.76?

Answer 8

E0 of H+/H2> E0 of Zn2+/Zn
Therefore H+ can oxidise Zn

Question 9

Will Au E0 1.68 V react with O2 E0 1.23 V?

Answer 9

No as E0 Au> E0 of O2 therefore O2 can’t oxidise Au

Question 10

Why Zn reduces aq solution of VO2+ tobV2+ but no further

Answer 10

E0 of v3+/V2+> E0 Zn2+/Zn
but
E0 of V2+/V< E0 Zn2+/Zn

Question 11

Hydrogen electrode

Answer 11

Always on LHS

Question 12

Purpose of argon when extracting Totanium using Mg

Answer 12

Prevent Mg from oxidising

Question 13

Why X colour arises?

Answer 13

Visible light is absorbed and d electrons are excited
Only X light is transmitted/reflected

Question 14

How heterogeneous catalysts occurs

Answer 14

1. Adsorption- reactants bind into active site of the surface of catalysts. Adsorbs at active site
2. Reaction- bonds in reactants weaken nd reaction takes place
3. Desorption- products desorb and released from active site
   Ie. Catalytic cracking of alkanes with zeolite catalyst
   Ie. Haber process

Question 15

Why may a support medium be needed.

Answer 15

Reaction occurs at active site on surface and a support medium may be needed to maximise surface area of catalyst and minimise the costs
You can use powder/pellets or mesh catalyst

Question 16

Efficiency of heterogeneous catalysts

Answer 16

Can be poisoned by impurities that block the active site
-reduced efficiency and has cost implications

Haber process- iron poisoned by sulfur
Catalytic converters- platinum poisoned by lead

Question 17

Autocatalysis

Answer 17

2MnO4- +5C2O4- +16H+ —> 2Mn2+ +10CO2+8H20
Slow at 1st as reactants are both negative ions therefore repel each other and ae is high

Question 18

Why BaCl2 used to test for surface ions and why it is acidified?

Answer 18

Other anions would give a negative result which is no ppt forming
Acidified so white ppt forms