Chp 3- Metals And Non Metals

Question 1

How many element a are present?

Answer 1

118- total element 
92- nature
26- artificial 
89-metals
22-  non metal
8- metallois

Question 2

What are the physical properties of metals? state the uses of few metals

Answer 2

• are generally hard except alkali metals like Na, K,Li
• are generally solid except Hg,
• are ductile( most ductile-gold-2km wire from 1gm )
  -sonorous
  -Malleable - max in Au and Ag
• have high melting pt(except Ga,Caesium, Na, K,Li)
  -high boiling pt
  -Are good conductors Of heat
  (best- silver, copper ; poor- Lead and mercury)
• good conductors of electricity( except tungsten(W), bismuth)
  -have high tensile strength
  -high density (except Na, K,Li)

chromium - assists in metabolism of sugar
cobalt- present in vitamin B12
Mangnese- role in maintaining proper calcium levels in bones.
copper- involved in production of red blood cells

Question 3

What are metalloids?

Answer 3

Those substances that have common properties of both metals and non metals. The eight elements classified as metalloids are boron, silicon, germanium, arsenic, antimony, tellurium, astatine, and polonium.

Question 4

Why are electric wires are coated with PVC or a rubber-like material?

Answer 4

Electric wires and cables are coated with substance like PVC(polyvinyl chloride) to prevent from electric shock since PVC is insulator pad conductor of electricity). and it does not conduct electricity it is therefore on excellent material to use for electrical applications such as insulation sheathing for cables.

Question 5

Physical properties of non metals

Answer 5

• Non-metals may be either solids, liquids or gases.
• Solid non-metals are brittle and break down into powdery mass on striking with a hammer except diamond which is the hardest non-metal.
• No luster but iodine n graphite is lustrous.
• They have low melting points except graphite that has very high melting point.
• They are poor conductors of heat and electricity except graphite.
• They are not malleable.
• They are not ductile.
• They are not sonorous.
• low tensile strength
• low densities

Question 6

tell-
1) first 4 most abundant elementsn present in our body 
2 ) top 5 abundant metals
3) hardest metal
4) softest metal

Answer 6

most abundant elements in body-

1) o2- 65%%
2) carbon 18%
3) H2- 10%
4) Nitrogen- 3%

Top 5 metals-

1) Aluminium
2) iron
3) calcium
4) sodium
5) magnesium
6) potassium

hardest metal- chromium
softest metal- cesium

Question 7

why do metals posses lustre?

Answer 7

when light falls on the surface of th metals, the atoms absorb photons as energy. they get excited and start vibrating. these vibrating e- release the light in the form of energy.

Question 8

how metals conduct elctricity?

Answer 8

metals conduct heat by the process of conduction . when we heat a piece of metal, metal atoms gain nergya and start vibrating . during vibration, they transfer their energy to neighbouring atom and the neighbouirng atom repeats the same.

Question 9

1) why are metals regarded as electropositive elements?
2) what is the chemical properties of metals linked with?
3) why do Non-metals not react with water

Answer 9

1) metals in general have the tendency to lose 1,2,3 e- to from positive ions. thus are called electropositive elements.
2) the chemical prop of the metals are mostly linked with the electron releasing tendency of the atoms. Greater the tendency, more will be the reactivity.
3) Non-metals are electronegative and are unable to break the bond between H and O in water. The non metals cannot reduce hydrogen by donating electrons. Thus, non-metals do not react with water.

Question 10

t/f-

1) metal oxides and non metal,s oxides are ionic in nature.
2) All non metal oxides are acidic in nature
3) copper doesn’t react with HCL
4) the combining power of an atom is valency

Answer 10

1) F, metal oxides are ionic in nature however NM oxides are covalent. for eg- sodium oxide ,potassium oxide,Carbon dioxide, Nitrogen dioxide are covalent.
2) F, water, Carbon monoxide, Nitrous oxide(N2O), Nitric oxide(NO) are neutral

3) in the case of reaction copper and HCL , no bubbles were seen and the temp remains unchanged.
4) True

Question 11

what happens when Na, K, Mg, Cu, Al, Au and Ag are burned in O2

Answer 11

Na and K react vigorously to form their oxides. sodium burns with a golden yellow flame while K with a lilac flame.
Mg burns easily with white flame to form MgO
Cu and Al do not burn but on heating in air form blank CuO and Al2O3. these metals oxides are found to be insoluble in water.
Au and Ag do not react with oxygen and water even at high temp.

Question 12

Why is sodium n K stored in kerosene but not Li

Answer 12

Due to high reactivity of Na and K with oxygen, they are kept in kerosene. If they are kept in air they will react with oxygen to form their respective oxides.
Lithium cannot be stored in kerosene oil because it is the lightest metal and it floats on its surface and reacts with air. Thus, it is kept wrapped in paraffin wax.

Question 13

Give examples of

1) metal oxides that react with water
2) amphoteric

Answer 13

Na2O + H2O = 2NaOH
(Metal oxides react with water to form alkalis however most metals oxides are insoluble in water.)

1- With alkali-
2NaOH + Al2O3 = 2NaAlO2 + H2O
(sodium meta aluminate)
ZnO+ NaOH= Na2ZnO2+ H2O

2-With acid
6HCl + Al2O3 = 2AlCl3 +
3H2O

Question 14

What is anodising?

Answer 14

At ordinary temperature, the surfaces of metals such as magnesium, zinc and lead, etc. are covered with a thin layer of the oxide. The protective layer of the oxide prevents the metal from further oxidation.

Anodising is a process of forming a thick oxide layer of aluminium. Aluminium develops a thin oxide layer when it exposed to air. This oxide coat of aluminium (Al) makes it resistant to further corrosion. During anodising, the resistance can be improved further by making the oxide layer thicker. In this process, a clean Al article is made the anode and dilute sulphuric acid is used for electrolyte. The oxygen gas evolved at the anode react with Al to make a thicker protective oxide layer. This oxide layer can be dyed easily to give Al articles an attractive finishing.

Question 15

Explain the reaction of metals with water.

Answer 15

Metal reacts with water and produce a metal oxide and hydrogen gas. Metal oxides that are soluble in water dissolve in it to form metal hydroxide. But all metals do not react with water.

• Metals like potassium and sodium react violently with cold water. In case of sodium and potassium, the reaction is so violent and exothermic that the evolved hydrogen immediately catches fire.
• reaction of calcium with water is less violent. The heat evolved is not sufficient for the hydrogen to catch fire. Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal.
• Magnesium does not react with cold water. It reacts with hot water to form magnesium hydroxide and hydrogen. It also starts floating due to the bubbles of hydrogen gas sticking to its surface.
• Metals like aluminium, iron and zinc do not react either with cold or hot water. But they react with steam to form the metal oxide and hydrogen.
• Metals such as lead, copper, silver and gold do not react with water at all.

Question 16

What is royal water?

Answer 16

Aqua regia is a Latin word it means “royal water”. It is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3: 1. It is a highly corrosive, fuming liquid and is used to dissolve gold and platinium.
The two acids in a freshly prepared aqua regia combine to evolve nascent Chlorine (Cl). This nascent chlorine dissolves metals. Aqua regia form chlorides of Au and Pt. Thus it oxidises these metals and form their chlorides.

Question 17

Why is h2 not released A when a metal reacts with nitric acid?

Answer 17

Hydrogen gas is not evolved when a metal reacts with nitric acid. because HNO is a strong oxidising agent. It oxidises the H, produced water and itself gets reduced to any of the nitrogen oxides (N₂O, NO,NO₂). But magnesium (Mg) and manganese (Mn) react with very dilu HNO3, to evolve H₂ gas.

Question 18

Reaction of copper and hot concentrated H2SO4

Answer 18

copper reacts with hot concentrated sulphuric acid (H₂SO4) to produce copper sulphate, sulphur dioxide and water.

Cu(s)+2H₂SO4(aq)=CuSO4(aq)+ 2SO₂(g) + 2H₂O(0)

Question 19

Explain the reaction between metals with soln of other metal salts with the eg of reaction of copper with silver nitrateZ

Answer 19

When a strip of copper metal is placed in a solution of AgNO3, the solution becomes gradually blue due to the formation of copper nitrate and a shining coating of silver metal gets deposited on the copper strip. The reaction may be written as:

2AgNO3+ Cu→ Cu(NO3)₂+ 2Ag
Silver. (blue)

However, if we place silver wire in a copper sulphate solution no reaction occurs. This means copper can displace silver from its salt solution but silver cannot displace copper from its solution.

Question 20

What is reactivity series and why even when hydrogen is not a metal, it is kept in reactivity series

Answer 20

Reactivity series is the list of the metals arranged in the order of their decreasing reactivity.
hydrogen is not a metal but even then it has been placed in the reactivity series because hydrogen can also lose electron and form positive ion (H+) like metals.

Question 21

T/F ionic compounds exist as molecules

Answer 21

False: ionic com-pounds do not exist as molecules but aggregates of oppositely charged ions. These compounds do not bear any charge i.e. they are neutral.They are held together by a strong electrostatics force of attraction.

Question 22

Define electrovalent bond n electrovalency

Answer 22

Electrovalent bond or ionic bond may be defined as the electrostatic force of attraction which holds the oppositely charged ions together or it may also be defined as a chemical bond formed between two atoms by complete transfer of electrons from one atom to another so as to complete their octet and hence acquire the stable nearest noble gas configuration.

The number of electrons lost or gained by the atom is called its electrovalency.

Question 23

What are the properties of ionic compounds

Answer 23

Physical nature: Ionic compounds are solids and are somewhat hard because of the strong force of attraction between the positive and negative ions. These compounds are generally brittle and
break into pieces when pressure is applied.

Melting and Boiling points: Ionic compounds have high melting and boiling points.This is because a considerable amount of energy is required to break the strong inter-ionic attraction.

Solubility: Electrovalent compounds are generally soluble in water(because if polar nature) and insoluble in solvents such as kerosene, petrol, etc.

Conduction: lonic compounds in the solid state do not conduct electricity because movement of ions in the solid state is not possible due to their rigid But they can conduct electricity in molten or aqueous state. Metals and ionic compounds are both solids. Where metals like copper and silver conduct electricity as such, the ionic solids do so either in the molten state or in solution.

Colour to the flame: Most of the salts when brought into the flame, impart characteristic colour to the flame.

Question 24

Why are different flame produced?

Answer 24

Flame colors are produced from the movement of the electrons in the metal ions present in the compounds as they gain thermal energy.
Sodium- yellow golden
K- lilac/ violet
Ba- Green

The flame test is a qualitative test used in chemistry to help determine the identity of a metal found in an ionic compound.