chapter 14: metals

Question 1

why are pure metals not used in industry?

Answer 1

1. pure metals are soft
   > in pure metal, atoms are packed regularly in layers
   > layers of atoms can slide over one another easily when a force is applied
   * metal atoms of the same size
2. pure metals may react with air and water and wear away or corrode easily

Question 2

what are alloys?

Answer 2

• a mixture of a metal with one or few other elements

Question 3

why are metals often used in the form of alloys?

Answer 3

• they are stronger and do not wear away easily
  used for the following purpose:

1. to make harder and stronger metals
   > brass ( an alloy of zinc and copper) harder than pure copper or pure zinc

2.to improve the appearance of metals

3. to lower melting points of metals
   >solder ( alloy of tin and lead) lower melting point than most metals
   > used to join electronic parts to circuit boards
4. to make metals more resistant to corrosion
   > cupronickel ( alloy of copper and nickel)
   > used in coins cuz does not corrode easily

Question 4

why are alloys stronger and harder than their constituent metals?

Answer 4

• in alloys, atoms of different metals or elements
  > are different sizes which disrupts the regular arrangement of atoms in a pure metal
• the atoms of different sizes cannot slide over each other easily when a force is applied
  > alloy is stronger and harder than pure metal

Question 5

metal reactivity series

Answer 5

K: potassium
Na: sodium
Ca: calcium
Mg: magnesium

[C]

Zn: zinc
Fe: iron
Pb: lead

[H]

Cu: copper
Ag: silver
Au: gold

Question 6

what are displacement reactions of acids and what are some examples?

Answer 6

• a more reactive metal can displace a less reactive metal from its salt solution
• eg: when iron fillings added to solution of copper(II) sulfate
  >copper is precipitated out of the solution as a pink or reddish brown solid
  > the solution turns green
• the iron has displaced copper from the copper (II) sulfate solution

iron + copper(II) sulfate > iron(III) sulfate + copper

Question 7

what is the reaction between a metal an the oxide of another metal?

Answer 7

• a more reactive metal can reduce the oxide of a less reactive metal
• zinc + copper (II) oxide > zinc oxide + copper

Question 8

what is the reaction of metal and cold water?
+ which metals react with cold water?

Answer 8

• potassium
• sodium
• calcium
• magnesium

metal + water > metal hydroxide + hydrogen

• a more reactive metal reacts more violently with cold water

Question 9

what is the reaction of metal and steam?
+ which metals react with cold water?

Answer 9

• potassium
• sodium
• calcium
• magnesium
• zebra
• iron

metal + steam > metal oxide + hydrogen

• a more reactive metal reacts more violently with steam

Question 10

what is the reaction of metals with dilute hydrochloric acid?

Answer 10

• metals react with dilute acids to produce salt and hydrogen

metal + dilute HCl > metal chloride and hydrogen

Question 11

reduction of metal oxides with carbon.

Answer 11

• metal oxide + carbon»_space;(heat)» metal + carbon dioxide
• the more reactive a metal is, the more difficult it is to reduce its oxide to the metal by carbon

Question 12

what is the importance of reduction of metal oxides with carbon in the industry?

Answer 12

• metals need to be extracted from their ores ( which are naturally-occurring compounds)
  > ores are mainly made of metal oxides

in the industry,
- metals that are below magnesium in the reactivity series are often extracted by reduction with carbon
- the metal oxides above zinc in the reactivity series are often not reduced by carbon
> oxides are very stable and are usually reduced by passing electricity through them

Question 13

reduction of metal oxides with hydrogen

Answer 13

• metal oxide + hydrogen > metal and steam
• the more reactive a metal is, the more difficult it is to reduce its oxide to the metal by hydrogen

Question 14

what is the action of heat on metal carbonates?

Answer 14

• the more reactive a metal is, the more difficult it is to decompose its carbonate by heat
• sodium and potassium are higher up the reactivity series
  > carbonates are very stable to heat
• the carbonates of metals below sodium in the reactivity series decompose to form the oxides of the metals and carbon dioxide
• for silver carbonate, the silver oxide produced is thermally unstable
  > further decomposes to form silver

Question 15

which metals are extracted by electrolysis and why?

Answer 15

• potassium
• sodium
• calcium
  -magnesium

> these metals are reactive
compounds are very difficult to be broken down
metals can only be extracted using electricity called electrolysis

Question 15

which metals are extracted by electrolysis and why?

Answer 15

• potassium
• sodium
• calcium
  -magnesium

> these metals are reactive
compounds are very difficult to be broken down
metals can only be extracted using electricity called electrolysis

Question 16

which metals are extracted by carbon and why?

Answer 16

• zinc
• iron
• lead
• copper
  -silver
• these metals are not so reactive
  > they are readily extracted by reducing their oxides with carbon

Question 17

blast furnace

Answer 17

i lazy