trnaisiton metals

Question 1

what is a catalyst

Answer 1

• A substance which increases the rate of a chemical reaction
• Without being used up

Question 2

how does a catalyst work

Answer 2

• Provide an alternative reaction pathway
• With a lower activation energy

Question 3

what is a heterogenous catalyst

Answer 3

Heterogeneous – where the catalyst is in a DIFFERENT phase to the reactants

Question 4

what is a homogenous catalyst

Answer 4

Homogeneous – where the catalyst is in the same phase as the reactants

Question 5

how does a heterogenous catalyst work?

Answer 5

(1) Reactants adsorb onto the surface of the catalyst on an active site.

(2) Reaction occurs on the surface of the catalyst

(3) Products desorb from the surface if the catalyst

Question 6

how are catalysts made as efficient as possible

Answer 6

• Increase the surface area
• Spread the catalyst over an inert support medium.

Question 7

how does poisoning effect catalysts

Answer 7

• Impurities can block the active sites.
• This prevents the reactants from adsorbing
• Purifying the reactants is the best way to prevent poisoning.

Question 8

an example of a heterogenous catalyst in harber process

Answer 8

Making Ammonia in the Haber Process

Catalysed by solid IRON

Question 9

an example of heterogenous catalyst in the contact process

Answer 9

Making Sulfuric Acid in the Contact Process

Catalysed by solid Vanadium (V) Oxide – V2O5

Question 10

how do transition metals catalyse homogenously

Answer 10

Transition metals have variable oxidation states, so they can act as catalysts.

Question 11

what group cannot catalyse

Answer 11

group 1

Question 12

why can group one not be catalysts

Answer 12

Group 1 metals don’t catalyse reactions as they only exist in one oxidation state.

Question 13

why does an uncatalysed reaction have a high EA

Answer 13

The uncatalyzed reaction has a high Ea as the two negative ions repel each other

Question 14

what is autocatalysis

Answer 14

one of the products of the reaction actually catalyses the reaction as it proceeds further.

Question 15

an example of autocatalysis is

Answer 15

oxidation of ethanedioic acid by manganate (VII) ions.

Question 16

hoe can a reaction be self indicating

Answer 16

• As MnO4- reacts to form Mn2+ it turns from deep purple to colourless.
• As the MnO4- is added to the Fe2+ solution it decolourises as it reacts.
• As soon as all the Fe2+ is reacted, the reaction mixture will start to turn purple as the MnO4- has nothing to react with.

Question 17

Whenever transition metal redox reactions take place in acidic conditions, what shouldn’t occur

Answer 17

HCl should NEVER be used to acidify the solution.

Question 18

what are the features of transition metals

Answer 18

· Transition Elements form Complex Ions

· Coloured Ions – Many Transition Metal compounds are different colours.

· Catalytic Properties – Many Transition Elements and compounds formed from Transition Elements can act as catalysts.

· Variable Oxidation States – Transition Elements form compounds in which the metal can be in different oxidation states.

Question 19

why can XCl4 only form 4 co ordinate bonds

Answer 19

The chlorine atoms are too big to fit more than 4

Question 20

what bonds does EDTA4- form

Answer 20

EDTA4- can form six coordinate bonds; two coordinate bonds form from the N atoms, and four coordinate bonds form the O- atoms.