metallurgy

Question 1

the method used to separate ore from gangue by preferential wetting

Answer 1

froth flotation

Question 2

a compound added to lower the fusion temp of electrolytic bath in the extraction of aluminium

Answer 2

cryolite

Question 3

ore of zinc containing its sulphide

Answer 3

zinc blende

Question 4

metals present in cryolite

Answer 4

sodium, fluorine, aluminium

Question 5

black powdery substance used for the reduction of zinc oxide during its extraction

Answer 5

coke

Question 6

the substance is an alloy of zinc, copper and tin

Answer 6

bronze

Question 7

electrolytic deposition of a superior metal on a base metal

Answer 7

electroplating

Question 8

an alloy used to make statues

Answer 8

bronze

Question 9

the most common ore of iron

Answer 9

haematite

Question 10

the raw materials required for the extraction of iron from haematite are ____, ____ and hot air. the minerals present in haematite is _____ which is reduced by _____ to iron

Answer 10

a. coke
b. limestone
c. iron II oxide
d. carbon monoxide

Question 11

why is platinum, gold and silver used to make jewellery

Answer 11

they are resistant to the attacks of air, water and acids

Question 12

why cant aluminium oxide be reduced by a reducing agent

Answer 12

al2o3 is a highly stable compound and Al has a strong affinity for oxygen

Question 13

why are carbonate and sulphide ores usually converted into oxides during the process of extraction

Answer 13

it is easier to reduce oxides to the respective metal than the sulphide and carbonate ores

Question 14

why is aluminium used to make flash bulbs

Answer 14

Al burns in oxygen producing an intense white light. this property makes it suitable for flash bulbs

Question 15

state 2 diff between roasting and calcination

Answer 15

calcination:
1. ore is heated in the absence/ limited supply of air
2. used for carbonate ores

roasting:
1. ore is heated in the presence of air
2. used for sulphide ores